Initiation of Locomotion in Lampreys

Cross references:   Lamprey Locomotion   Lamprey Nervous System      
Lamprey Neurotransmitters          Lamprey GABA          Lamprey Motor Nerves    
Lamprey Fast-Slow Twitch    Amphioxus Locomotion       Salamander Locomotion  
Tonic Inhibition  
    Locomotion Sequence   


Is the  Cerebellum   a major source of behavioral excitation?

Cerebellum The cerebellum does not initiate movement, but it contributes to coordination, precision, and accurate timing.  It receives input from sensory systems and from other parts of the brain and *spinal cord, and integrates these inputs to fine tune motor activity. [2]"
    My comment
So.  If Cerebellum is not a major source of behavioral excitation, what is?  Maybe I should go back and take another look at these references.  



1976    320<349 
    "It was concluded that a spinal central network can account for the phase lag observed between successive segments during swimming."  
My comment
    This was the oldest reference to have an Abstract. 
No mention of neurotransmitters.


My comment
    There isn't any Abstract, but I thought the mention of a specific neurotransmitter warranted particular attention.     
    5<67 
    "Our findings indicated that GABAergic and glycinergic synapses played different roles in modulating neurochemically induced locomotion rhythms. GABAergic inhibition regulated the onset and duration of neurochemically induced locomotor-like rhythms, and glycinergic inhibition stabilized the pattern of the alternating rhythms."  
    Neurotransmitter:  glycine 


1981    302<349

Activation of NMDA-receptors elicits "fictive locomotion" in lamprey spinal cord in vitro.
My comment:

    There isn't any Abstract, but I thought the mention of a specific receptor warranted particular attention.     
    There were 97 Similar Articles:
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=6291323  
    Receptor:  NMDA 



1983   299<349 
The neural generation of locomotion in the lamprey: an incomplete account.
    No Abstract, but the title looked interesting. 
    Similar article.
    Neurotransmitter:  glutamate 
See:  Central Pattern Generators 


1983  298<349   
On the spinal generation of locomotion, with particular reference to a simple vertebrate: the lamprey.
    No Abstract, but the title looked interesting. 


1985 289<349
N-Methyl-D-aspartate (NMDA), kainate and quisqualate receptors and the generation of fictive locomotion in the lamprey spinal cord.

    "
The motor pattern underlying swimming can be elicited in an in vitro preparation of the lamprey spinal cord by applying excitatory amino acids in the bath activating N-methyl-D-aspartate (NMDA) receptors and kainate receptors, but not quisqualate receptors." 
    "
The findings further consolidate that NMDA receptors are efficient and demonstrates that kainate can also be effective in inducing fictive locomotion, and also that activation of either receptor type is sufficient.." 
    "It is suggested that these effects, presumably via aspartate and/or glutamate actions, are exerted on the input stage of interneuronal network."  
    Receptors:   NMDA, kainate, quisqualate 
    Neurotransmitters:  aspartate, glutamate (excitatory amino acids) 



    Receptor:  NMDA 
See:  Lamprey Neurotransmitters  for partial Abstract, Related citations and Cited by's. 


1985    279<349
The role of putative excitatory amino acid neurotransmitters in the initiation of locomotion in the lamprey spinal cord. I. The effects of excitatory amino acid antagonists. 
     The activation of N-methyl-D-aspartate (NMDA) and kainate receptors will evoke fictive locomotion in the appropriate motor pattern for locomotion in the isolated lamprey spinal cord, but not a selective activation of quisqualate receptors. The present experiments test whether the initiation of locomotion in response to sensory stimulation depends on these types of receptors.  
    An in vitro preparation of the lamprey spinal cord with part of its tailfin left innervated has been used. In this preparation a sequence of fictive locomotion (i.e. alternating bursts in the segmental ventral roots with a rostrocaudal phase lag) can be elicited by continual sensory stimulation of the tailfin. The effects of excitatory amino acid antagonists were studied by recordings from ventral roots (extracellularly) and motoneurones (intracellularly). It was found that the strong initial bursts of each swimming sequence induced by sensory stimulation were depressed by combined NMDA/kainate antagonists (cis-2,3-piperidine dicarboxylate (PDA) and gamma-D-glutamylglycine (gamma-DGG] whereas the less intense burst activity, occurring particularly towards the end of each swimming sequence, was depressed by a selective NMDA antagonist, 2-amino-5-phosphonovalerate (2-APV). This condition could be mimicked in an isolated spinal cord preparation by an application of L-glutamate; the low-level fictive locomotion induced by low doses of L-Glu (less than 100 microM) was depressed by a NMDA antagonist (2-APV), and, if higher doses were applied, the activity was only depressed by PDA/gamma-DGG.  
    The mode and time course of the depression (by excitatory amino acid antagonists) of fictive locomotion, induced by sensory stimulation, shows that the putative excitatory amino acid neurotransmitter directly or indirectly acts at the pattern generating circuitry within the spinal cord."  
    Neurotransmitters: L-glutamate,  excitatory amino acids and their antagonists.  Externally applied.   


1985   
278<349
The role of putative excitatory amino acid neurotransmitters in the initiation of locomotion in the lamprey spinal cord. II. The effects of amino acid uptake inhibitors. 
    "
Fictive locomotion can be evoked in an in vitro preparation of the lamprey spinal cord by an activation of N-methyl-D-aspartate (NMDA) or kainate receptors. To obtain further knowledge of the putative transmitters underlying this activation the effects of L-glutamate and L-aspartate were examined.  
    These endogenous amino acids exerted a distinctly different effect as compared to the synthetic amino acids (N-methyl-D,L-aspartate and kainate) previously tested. In a wide dose range L-glutamate and L-aspartate elicited fictive locomotion only when the bathing solution was rapidly circulated over the spinal cord surface. In the absence of fluid circulation the activity rapidly ceased. To test if this effect was due to an uptake of amino acids, two amino acid uptake inhibitors were administered. After exposure to p-chloromercuriphenylsulphonate (pCMS) or dihydrokainate (DHK), L-glutamate and L-aspartate elicited continuous fictive locomotion independently of whether the bathing fluid was circulated or not. This treatment also markedly lowered the threshold doses of L-glutamate and L-aspartate, while the effects of NMA and kainate were barely affected. Fictive locomotion induced by sensory stimulation of the tailfin was also prolonged by dihydrokainate.    
    These findings suggest that a highly effective amino acid uptake system is present in the lamprey spinal cord and furthermore that it takes part in the inactivation of synaptically released acidic amino acid neurotransmitters, which are of importance for the initiation of locomotion."  
    Neurotransmitters:  Excitatory amino acids and their uptake inhibitors.    Externally applied.   


   
    Neurotransmitters:  5-HT 
    My comment
Although not clearly stated, it seems that the "fictive locomotion" might be due to a central pattern generator. 
    Receptor:  NMDA   



1986    273<349     
Free Article   
Dual-component synaptic potentials in the lamprey mediated by excitatory amino acid receptors.
    "The synaptic mechanisms underlying amino acid-mediated excitation in the lamprey spinal cord have been investigated. Fine stimulating electrodes were used to stimulate single axons in the spinal cord and evoke unitary EPSPs in lamprey motoneurons and one type of premotor interneuron, the CC interneuron. Three types of EPSP, distinguished by their time course and sensitivity to amino acid antagonists, were seen."  
    My comment
Although there's no explicit mention of "central pattern generators", there is a clear statement that the lamprey spinal cord is excited by amino acids.  
   

1987
270<349  
Single sensory neurons activate excitatory amino acid receptors in the lamprey spinal cord.   
    "
Stimulation of individual dorsal cells evoked mono- and/or polysynaptic excitatory postsynaptic potentials (EPSPs) in giant interneurons.   ... mechanosensory neurons in the lamprey spinal cord activate EAA receptors (kainate/quisqualate receptors) on interneurons, via mixed chemical and electrical synapses."  
    My comment
If I understand correctly, monosynaptic postsynaptic potentials imply a direct connection between the sensory cells and the motor cells.  This would rule out transmission through the thalamus. 
    Receptors:  excitatory amino acid 


1987   
269<349  
Reticulospinal neurones activate excitatory amino acid receptors. 
    "...
5-phosphonovalerate caused a selective depression of a late component of the EPSP. Thus, fast-conducting reticulospinal neurones appear to release an excitatory amino acid acting at both NMDA and non-NMDA receptors."  
    Neurotransmitter 5-phosphonovalerate
    Receptors:  NMDA, non-NMDA   



1988    260<349   
A new class of small inhibitory interneurones in the lamprey spinal cord. 
    "
This type of interneurone undergoes rhythmical membrane potential oscillations during fictive locomotion and intracellular stimulation can have a profound effect on the burst generation occurring during fictive locomotion."  

    My hypothesis
Oscillations = Pattern.  
Central Pattern Generator = Central Oscillation Generator.   
    Neurotransmitter:  glycine 


1989   249<349 
Further evidence for excitatory amino acid transmission in lamprey reticulospinal neurons: selective retrograde labeling with (3H)D-aspartate. 
    "
The (3H)D-aspartate labeling correlates with previous electrophysiological studies showing that lamprey reticulospinal neurons utilize excitatory amino acid transmission."  
    My comment
It would be interesting to know which "excitatory amino acids" are utilized.     


1989   247<349 
Effects of 5-hydroxytryptamine on the afterhyperpolarization, spike frequency regulation, and oscillatory membrane properties in lamprey spinal cord neurons. 
    My comment
I don't know much about cell electrophysiology, so I didn't really understand this.  Sounds like CPG's. 
    See:  Rhombencephalon  for full Abstract, Related citations and Cited by's.   
    Neurotransmitters:  excitatory amino acids.
    See:  Lamprey GABA   for full Abstract, Similar articles & Cited by's. 
    Neurotransmitters:  GABA . 
    See:   GABA/Glycine Inhibition   for full Abstract, Related citations and Cited by's. 
    Neurotransmitters: (neuromodulators?)  GABA . 
    Neurotransmitter:  5-HT


1993    199<349   
Dorsal root and dorsal column mediated synaptic inputs to reticulospinal neurons in lampreys: involvement of glutamatergic, glycinergic, and GABAergic transmission   
http://www.ncbi.nlm.nih.gov/pubmed/8381143       
    "
This study was aimed at characterizing the inputs from dorsal roots and dorsal columns to reticulospinal neurons within the posterior rhombencephalic reticular nucleus in the lamprey. ... Taken together, the present results suggest that dorsal root and dorsal column stimulations give rise to disynaptic inhibition and excitation of reticulospinal neurons mediated by excitatory and inhibitory amino acid transmission via brainstem interneurons."  
    See:  Lamprey GABA  for full Abstract, Similar articles and Cited by's. 
    Neurotransmitters
glutamate, glycine, GABA 



1995    173<349
Neural networks that co-ordinate locomotion and body orientation in lamprey.  
http://www.ncbi.nlm.nih.gov/pubmed/7571002   
    "
The networks of the brainstem and spinal cord that co-ordinate locomotion and body orientation in lamprey are described. 
    The cycle-to-cycle pattern generation of these networks is produced by interacting glutamatergic and glycinergic neurones, with NMDA receptor-channels playing an important role at lower rates of locomotion. The fine tuning of the networks produced by systems involves a modulation of Ca2+-dependent K+ channels, high- and low-threshold voltage-activated Ca2+ channels and presynaptic inhibitory mechanisms."  
    Neurotransmitters:   
glutamate, glycine     
    Receptors:   
NMDA 


1995   172<349   
Reticulospinal neurones provide monosynaptic glycinergic inhibition of spinal neurones in lamprey. 
http://www.ncbi.nlm.nih.gov/pubmed/8527722   
See:   Inhibition of Locomotion in Lampreys   for Abstract and Similar articles.
    Neurotransmitter:   
glycine 


1995
   171<349
Trigeminal inputs to reticulospinal neurones in lampreys are mediated by excitatory and inhibitory amino acids.   
    Neurotransmitters:   
excitatory and inhibitory amino acids 
    inputs rather than CPG
See:  Lamprey Neurotransmitters  for full Abstract, Related citations and Cited by's. 



1996    168<349
Monosynaptic input from cutaneous sensory afferents to fin motoneurons in lamprey.   

    See: 
Lamprey Sensory Nerves  .   
    CPG rather than input


1996   
164<349
Rostrocaudal distribution of 5-HT innervation in the lamprey spinal cord and differential effects of 5-HT on fictive locomotion. 
    Neurotransmitter:    5 -HT   
    See:  Lamprey Neuropeptides  
    Neuropeptides:   
tachykinins,  substance P 


1997   
150<349
Diencephalic projection to reticulospinal neurons involved in the initiation of locomotion in adult lampreys Lampetra fluviatilis. 

   
See:  Initiation of Locomotion in Lampreys for full Abstract, Related citations and Cited by's. 



1998   
147<349     
Substance P modulates NMDA responses and causes long-term protein synthesis-dependent modulation of the lamprey locomotor network.   
http://www.ncbi.nlm.nih.gov/pubmed/9614253    
    "
Tachykinin immunoreactivity is found in a ventromedial spinal plexus in the lamprey. Neurons in this plexus project bilaterally and are thus in a position to modulate locomotor networks on both sides of the spinal cord. We have examined the effects of the tachykinin substance P on NMDA-evoked locomotor activity. Brief (10 min) application of tachykinin neuropeptides results in a prolonged concentration-dependent (>24 hr) modulation of locomotor activity, shown by the increased burst frequency and more regular burst activity. These effects are blocked by the tachykinin antagonist spantide II."  
    "
The effects of substance P were mimicked by the dopamine D2 receptor antagonist eticlopride. The effects of eticlopride were blocked by the tachykinin antagonist spantide II, suggesting that eticlopride may endogenously release tachykinins. Because locomotor activity in vitro corresponds to that during swimming in intact animals, we suggest that endogenously released tachykinins will result in prolonged modulation of locomotor behavior."  
    5 Cited by's
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=9614253  
   
Free Article 
http://www.jneurosci.org/content/18/12/4800.long   
    Neuromopeptide   
    See:   Lamprey Neuropeptides for full Abstract. 


1998   
139<349
Endogenous activation of metabotropic glutamate receptors contributes to burst frequency regulation in the lamprey locomotor network.   
    "
The effect of metabotropic glutamate receptor (mGluR) agonists and antagonists on the spinal cord network underlying locomotion in the lamprey has been analysed."  
    "
The group III mGluR agonist L-2-amino-4-phosphonobutyric acid The group III mGluR agonist L-2-amino-4-phosphonobutyric acid reduced intraspinal synaptic transmission and burst frequency. and burst frequency."  
    Receptors
mGluR 
    CPG:
intraspinal synaptic transmission and burst frequency. 


1999    134<349
Activity-dependent metaplasticity of inhibitory and excitatory synaptic transmission in the lamprey spinal cord locomotor network.       
Free Article   
    "
Trains of spikes at 5-20 Hz were used to mimic the frequency of spiking that occurs in network interneurons during NMDA or brainstem-evoked locomotor activity.  
    Inputs from inhibitory and excitatory interneurons exhibited similar activity-dependent changes, with synaptic depression developing during the spike train. The level of depression reached was greater with lower stimulation frequencies. Significant activity-dependent depression of inputs from excitatory interneurons and inhibitory crossed caudal interneurons, which are central elements in the patterning of network activity, usually developed between the fifth and tenth spikes in the train."  
    Receotir
NMDA 
    CPG
excitatory interneurons and inhibitory crossed caudal interneurons, which are central elements in the patterning of network activity  



1999    133<349   
Interactive effects of the GABABergic modulation of calcium channels and calcium-dependent potassium channels in lamprey.     
Free Article 
    "
Activation of GABAB receptors reduces calcium currents through both low- (LVA) and high-voltage activated (HVA) calcium channels, which subsequently results in the reduction of the calcium-dependent potassium (KCa) current. This in turn will reduce the peak amplitude of the afterhyperpolarization (AHP)"  
    Receptor
GABAB 


1999   
126<349
Inhibition of N- and L-type Ca2+ currents by dopamine in lamprey spinal motoneurons. 
    "
Thus, dopamine mediates inhibition of N- and L-type currents through a G-protein-dependent, voltage-independent pathway in lamprey spinal motoneurons."  
    Neuromodulators:   
Dopamine


2000   
122<349
GABA(B)-ergic modulation of burst rate and intersegmental coordination in lamprey: experiments and simulations.
    "
Activation of GABA(B)-receptors in the lamprey spinal cord reduce both calcium currents and the peak amplitude of the post-spike afterhyperpolarization (AHP). Activation of GABA(B)-receptors reduce the segmental alternation rate and modifies the intersegmental coordination when the spinal locomotor circuits are activated by NMDA."  
    Receptor
GABAB 
    CPG
spinal locomotor circuits   


2000    121<349
The activity-dependent plasticity of segmental and intersegmental synaptic connections in the lamprey spinal cord.   
    "
Segmental inputs from glutamatergic excitatory interneurons (EIN) to ipsilateral glycinergic crossed caudal (CC) interneurons were facilitated or depressed during spike trains at 5-20 Hz. Connections between EINs were depressed. Glycinergic inputs from small ipsilateral inhibitory interneurons were depressed in motor neurons, but were facilitated in CC interneurons. Excitatory inputs from small crossing interneurons to motor neurons were depressed, whereas inhibitory inputs were unaffected. With the exception of connections between EINs, significant effects occurred with stimulation that mimicked interneuron spiking during network activity."  
    Neurotransmitters
glutamate, glycine 
    CPG:
rhythmic network activity


2000   
119<349 
The spinal 5-HT system contributes to the generation of fictive locomotion in lamprey.   
    "
In P. marinus a blockade of 5-HT1A receptors by spiperone reversibly increased the frequency and the coefficient of variation. This implies that there is an endogenous release of 5-HT during fictive locomotion that is important for the generation of locomotor activity.  
    In L. fluviatilis bath applied NMDA or D-glutamate evoked in most cases irregular activity. An addition of 5-HT (0.5-2 microM) rapidly stabilised the burst generation and led to a sustained fictive locomotion."  
    "...
these results indicate that activity in the intrinsic 5-HT system in the lamprey spinal locomotor network contributes significantly to the rhythm generation"  
    Receptors:   
5-HT, NMDA, glutamate 
    CPU
fictive locomotion 


2001   
111<349
Ion channels of importance for the locomotor pattern generation in the lamprey brainstem-spinal cord.     
Free PMC Article 
    "
The network consists of excitatory glutamatergic and inhibitory glycinergic interneurones with known connectivity."  
    "...
the roles of the different subtypes of Ca2+ channels and potassium channels that regulate integrated neuronal functions, like frequency regulation, spike frequency adaptation and properties that are important for generating features of the motor pattern (e.g. burst termination), are reviewed."  
    Neurotransmitters
excitatory glutamatergic and inhibitory glycinergic 
    Channels
Ca2+ channels and potassium channels   



2001  110<349
Gating and braking of short- and long-term modulatory effects by interactions between colocalized neuromodulators.  
  
Free Article 
    "
A single 10 min application of the tachykinin substance P evokes a short-term ( approximately 1 hr) presynaptic facilitation of glutamate release and the postsynaptic potentiation of NMDA responses. The latter effect induces a long-term (>24 hr) protein synthesis-dependent increase in the frequency of network activity."  
    "
Dopamine did not directly modulate the effects of substance P. However, it reduced the presynaptic interactive effect of 5-HT and thus gated the presynaptic potentiation of glutamatergic inputs by substance P."  
    Neurotransmitters:   
substance P, glutamate, dopamine, 5-HT 
    Receptor
NMDA 
    CPG
Spinal locomotor networks 



2003   98<349

Endogenous and exogenous dopamine presynaptically inhibits glutamatergic reticulospinal transmission via an action of D2-receptors on N-type Ca2+ channels.   
    "
Bath application of DA (1-50 micro m) reduced the amplitude of monosynaptic reticulospinal-evoked glutamatergic excitatory postsynaptic potentials (EPSPs)."  
    "
DA did not affect the response to extracellularly ejected d-glutamate, the postsynaptic membrane potential, or the electrical component of the EPSPs. DA thus acts at the presynaptic level to modulate reticulospinal transmission."  
    Neurotransmitters
DA, glutamate 


2004   86<349  
Free Article  
The spinal GABAergic system is a strong modulator of burst frequency in the lamprey locomotor network 
http://www.ncbi.nlm.nih.gov/pubmed/15190090      
    See:   Lamprey GABA 


2005    84<349
Mechanisms for selection of basic motor programs--roles for the striatum and pallidum
.
http://www.ncbi.nlm.nih.gov/pubmed/15935487
    See:  Tonic Inhibition for full Abstract, Similar articles and Cited by's




2006   
76<349
5-HT Modulation of identified segmental premotor interneurons in the lamprey spinal cord.
    "
Ipsilaterally projecting spinal excitatory interneurons (EINs) generate the hemisegmental rhythmic locomotor activity in lamprey, while the commissural interneurons ensure proper left-right alternation. 5-HT is a potent modulator of the locomotor rhythm and is endogenously released from the spinal cord during fictive locomotion."  
    "
Thus 5-HT is a very potent modulator of membrane properties and synaptic transmission of last-order segmental premotor interneurons. "  

    Neurotransmitters
    See:   Lamprey GABA  for full Abstract, Related citations and Cited by's. 


2007    70<349  
Descending GABAergic projections to the mesencephalic locomotor region in the lamprey Petromyzon marinus.     
http://www.ncbi.nlm.nih.gov/pubmed/17226790  

    "These results suggest that the GABAergic projections to the MLR modulate the activity of MLR neurons, which would be inhibited by GABA at rest."  
    See:  Lamprey GABA


2007   
68<349     Free Article   
Tectal control of locomotion, steering, and eye movements in lamprey. 
http://www.ncbi.nlm.nih.gov/pubmed/17303814   
    "This study addresses the role of tectum in integrating eye, body orientation, and locomotor movements as in steering and goal-directed behavior."  
    "
These results show that tectum can provide integrated motor responses of eye, body orientation, and locomotion of the type that would be required in goal-directed locomotion."  
Consideration of components above the reticular system will make this  Free Article  very useful.  I will most certainly be coming back to this.


2007  66<349    Free Article 
Endogenous tachykinin release contributes to the locomotor activity in lamprey.   

http://www.ncbi.nlm.nih.gov/pubmed/17360825

    "
These data indicate that an endogenous tachykinin release contributes to the ongoing activity of the locomotor network by modulating the glutamate-glycine neuronal network responsible for the locomotor pattern."  
    3 Cited by's
    Neurotransmitters
tachykinins, glutamate, glycine
    CPG
neuronal network responsible for the locomotor pattern.   


2007  65<349

GABA distribution in lamprey is phylogenetically conserved.
http://www.ncbi.nlm.nih.gov/pubmed/17480011  
      
     See: 
Lamprey GABA for full Abstract, Similar articles and Cited by's.     
    Neurotransmitter:   
GABA


2008  56<349    
Free Article   
Diencephalic Locomotor Region in the Lamprey
http://www.ncbi.nlm.nih.gov/pubmed/18596192      
    See:  Diencephaloreticular Transmission  for full Abstract, Related citations, Cited by's, 
Important highlights and Free Full Text  . 


2009  48<349    
Free full text   
Nitric oxide potentiation of locomotor activity in the spinal cord of the lamprey. 
    "
Our results demonstrate a significant role of NO in adult vertebrate motor control which, via modulation of both excitatory and inhibitory transmission, increases the locomotor burst frequency."  
    Neuromodulator
nitric oxide (NO) 
    CPG:
spinal networks generating locomotion   


2009    46<349    
Free PMC Article   
Simple cellular and network control principles govern complex patterns of motor behavior   
http://www.ncbi.nlm.nih.gov/pubmed/19901329     
    "
The vertebrate central nervous system is organized in modules that independently execute sophisticated tasks. Such modules are flexibly controlled and operate with a considerable degree of autonomy.  
    One example is locomotion generated by spinal central pattern generator networks (CPGs) that shape the detailed motor output. The level of activity is controlled from brainstem locomotor command centers, which in turn, are under the control of the basal ganglia.  
    By using a biophysically detailed, full-scale computational model of the lamprey CPG (10,000 neurons) and its brainstem/forebrain control, we demonstrate general control principles that can adapt the network to different demands. Forward or backward locomotion and steering can be flexibly controlled by local synaptic effects limited to only the very rostral part of the network. Variability in response properties within each neuronal population is an essential feature and assures a constant phase delay along the cord for different locomotor speeds.
"  
    My comment
I will definitely be coming back to this since I'm very interested in the influence that more recently evolved neural centers have on behavior. 
   

2009     45<349    
Free PMC Article   
Measured motion: searching for simplicity in spinal locomotor networks   
http://www.ncbi.nlm.nih.gov/pubmed/19896834   
    "
Spinal interneurons are organized into networks that control the activity and output of the motor system. This review outlines recent progress in defining the rules that govern the assembly and function of spinal motor networks, focusing on three main areas.  
    We first examine how subtle variations in the wiring diagrams and organization of locomotor networks in different vertebrates permits animals to adapt their motor programs to the demands of their physical environment.  
    We discuss how the membrane properties of spinal interneurons, and their synaptic interactions, underlie the modulation of motor circuits and encoded motor behaviors.  
    We also describe recent molecular genetic approaches to map and manipulate the connectivity and interactions of spinal interneurons and to assess the impact of such perturbations on network function and motor behavior."  

    My comment
I will definitely be coming back to this since I'm very interested in spinal motor networks and I expect that the   Free PMC Article   will be very helpful.   


3<143   2010
Descending brain neurons in larval lamprey: spinal projection patterns and initiation of locomotion.
http://www.ncbi.nlm.nih.gov/pubmed/20510243    
    See:  Initiation of Locomotion in Lampreys   for full Abstract, Related citations, Cited by's and full free text. 


2011   
Localization, pharmacology, and organization of brain locomotor areas in larval lamprey.
http://www.ncbi.nlm.nih.gov/pubmed/21081157    
    See:  Initiation of Locomotion in Lampreys  for full Abstract, Related citations and 
Free PMC Article 


2012   35<349     Free PMC Article   
The dopamine D2 receptor gene in lamprey, its expression in the striatum and cellular effects of D2 receptor activation
  .  
    See:  Striatum  for full Abstract .   


2014   17<349 
The lamprey blueprint of the mammalian nervous system   
    See:  Lamprey Nervous System   for full Abstract, Similar articles and Cited by's.  


1988 10<13
Synaptic organization of the striatum   
http://www.ncbi.nlm.nih.gov/pubmed/3069970   
    "The striatum, the main component of the basal ganglia, is composed of mainly one type of neuron, the so-called medium spiny neuron. This neuron cell type, which constitutes over 90% of striatal neurons, is the major output neuron of the striatum.  Combined ultrastructural neuroanatomical methods have elucidated the organization of afferent connectivity to these neurons.  
    The major physiologic function of striatal efferent activity appears to be inhibition of tonically active GABAergic neurons in the globus pallidus and substantia nigra pars reticulata."   
    See:  Medium Spiny Neurons 
    My comment
So the striatum can be seen as initiating locomotion by inhibiting the tonically active inhibitory output neurons of the globus pallidus and substantia nigra pars reticulata. 


1988
Brainstem command systems for locomotion in the lamprey: localization of descending pathways in the spinal cord.
http://www.ncbi.nlm.nih.gov/pubmed/3219560   
    "The lamprey brainstem contains a 'command system' which descends into the spinal cord to activate motor networks and initiate locomotion. In the present study, partial lesions were made in the rostral spinal cord in order to spare various tracts and determine which tracts carry the descending command signal to the spinal cord. Sparing the medial areas of the rostral spinal cord usually blocked both sensory-evoked and spontaneous locomotion, while sparing the lateral regions of the rostral spinal cord did not abolish voluntary locomotor activity.  
    Either the ventrolateral or dorsolateral spinal tracts could support the initiation of locomotion. Brainstem structures rostral to the mesencephalon were not necessary for the initiation of locomotor behavior.  
    The data indicate that the lateral spinal tracts contain a significant part of the descending command pathway for locomotion. In contrast, the medial spinal tracts were neither necessary nor usually sufficient to support locomotor behavior, suggesting that the larger reticulospinal Muller cells, which project in these tracts, do not contribute significantly to the initiation of locomotion."   
    195 Related citations
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=3219560   
    4 Cited by's:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=3219560      
    My comments
1.  No mention of neurotransmitters.  
2. 
The data indicate that the lateral spinal tracts contain a significant part of the descending command pathway for locomotion 
3.  "Brainstem structures rostral to the mesencephalon were not necessary  ..."  


1989
Monosynaptic excitatory amino acid transmission from the posterior rhombencephalic reticular nucleus to spinal neurons involved in the control of locomotion in Lamprey
http://www.ncbi.nlm.nih.gov/pubmed/2555456  
    See:  Rhombencephalon  for the full Abstract, Related citations and Cited by's.   
    My comments
1.  Unspecified "excitatory amino acids". 
2.  Reticulospinal. 


1994  
Role of excitatory amino acids in brainstem activation of spinal locomotor networks in larval lamprey.
http://www.ncbi.nlm.nih.gov/pubmed/7908851   
    "An in vitro brain/spinal cord preparation from larval lamprey was used to determine the role of excitatory amino acid (EAA) receptors in the descending activation of spinal locomotor networks.  
    The general EAA receptor blockers KYN, PDA, and DGG completely blocked locomotor activity initiated from the brainstem. The NMDA receptor blocker APV and the non-NMDA receptor blocker DNQX usually attenuated but did not block locomotor activity. Relatively long and short cycle times were attenuated about equally by APV or DNQX, and therefore the attenuation was not cycle time dependent.  
    Receptor blockers for EAAs attenuated locomotor activity, but often with little or no change in the cycle time of burst activity. Although both NMDA and non-NMDA receptors for EAAs are important for the descending initiation of locomotor activity in the lamprey, it is unclear whether these receptors are concentrated in areas of the spinal locomotor networks that control cycle time."  
    126 Related citations:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_p
ubmed&from_uid=7908851  
     My comments
1.  Unspecified "excitatory amino acids". 
2.  Brainstem.   
3. The two statements;
        "The general EAA receptor blockers KYN, PDA, and DGG completely blocked locomotor activity" 
    and   "Receptor blockers for EAAs attenuated locomotor activity" 
seem to be almost mutually contradictory.  I need to look into this more closely.  Perhaps the Related citations might help.         


1996 
A mesencephalic relay for visual inputs to reticulospinal neurones in lampreys. 
http://www.ncbi.nlm.nih.gov/pubmed/8773792      
    "Visual stimuli elicit motor responses in lampreys. These responses rely, in part, on the activation of reticulospinal (RS) neurones which constitute the main descending pathway in these early vertebrates. This study sought to identify and characterize possible mesencephalic relays for visual inputs to RS neurones of the rhombencephalon.  
    The anatomical substrate subserving this function was investigated by iontophoretically ejecting cobalt-lysine, a retrograde tracer, in the middle rhombencephalic reticular nucleus in the in vitro isolated brainstem preparation of young adult Petromyzon marinus. Several populations of cells were retrogradely labeled in the brainstem.  
    Of particular interest were the cell populations found on each side of rostral mesencephalon, located in the tectum and pretectum. There were, on average, 113 cells labeled contralateral to the injection site and 80 cells labeled ipsilateral to the injection site. The cells were morphologically similar on both sides, except that the contralateral group had larger cell bodies as compared to the group on the ipsilateral side.  
    To determine whether the axons of the cells contacted reticulospinal neurones, electrophysiological experiments were carried out in which the region containing these cells was microstimulated. Large post-synaptic potentials were recorded intracellularly in RS neurones. Furthermore, microstimulation of the optic nerve on the same side as the recorded cell (i ON) evoked responses with a pattern similar to those resulting from stimulation of the optic tectum contralateral to the cell recorded (co OT), except for the longer response latencies. Local ejection of xylocaine (1% lidocaine hydrochloride) or CNQX (1 mM) onto the co OT reversibly abolished the responses evoked from stimulation of the i ON. There were no significant effects observed when the drug was ejected onto optic tectum ipsilateral to the cell.  
    Taken together, the results from this study indicate that the crossed tectoreticular pathway is involved in relaying optic nerve inputs to RS neurones of the middle rhombencephalic reticular nucleus. Moreover, cells of origin of this pathway appear, in all respect, homologous to cells giving rise to the crossed tectobulbar pathway in other vertebrates."  
     216 Related citations
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=8773792  
    2 Cited by's. 
    My comments
1.  cobalt-lysine, a retrograde tracer 
2.  mesencephalic relays of visual stimulation 
3.  crossed tectoreticular pathway
4.  middle rhombencephalic reticular nucleus 
5.  This is an example of behavior which was initiated not by the  Substantia Nigra pars Compacta  (SNc) and not by the rhombocephalon but by sensory input.  This may turn out to be what is actually happening in most cases.      


1997   
Diencephalic projection to reticulospinal neurons involved in the initiation of locomotion in adult lampreys Lampetra fluviatilis.     
http://www.ncbi.nlm.nih.gov/pubmed/9421142   
    "Morphological and electrophysiological techniques were used to characterize a diencephalic projection from the ventral thalamus to reticulospinal neurons and its role in initiating rhythmic locomotor activity in the spinal cord of adult lampreys (Lampetra fluviatilis).   
    Injection of fluorescein-coupled dextran amine (FDA) into the rhombencephalic reticular nuclei labeled neurons in the ventral thalamus region on both the ipsilateral side and the contralateral side. Injection of FDA into the ventral thalamus labeled axonal projections in all reticular nuclei, but no direct projections were found to the spinal cord.  
    Extracellular stimulation of the ventral thalamus elicited monosynaptic excitatory postsynaptic potentials (EPSPs), polysynaptic EPSPs, and inhibitory postsynaptic potentials (IPSPs) in reticulospinal neurons in the posterior (prrn) and middle (mrrn) rhombencephalic reticular nuclei.  
    The monosynaptic EPSPs were blocked by the glutamate antagonist kynurenic acid and can be considered glutamatergic. The monosynaptic EPSPs were potentiated (up to 12 minutes) following a brief high-frequency stimulation.  
    Stimulation of the ventral thalamus induced rhythmic firing of reticulospinal neurons and elicited rhythmic burst activity in the spinal ventral roots. The projections from the ventral thalamus to the reticulospinal neurons in the prrn and mrrn thus provide excitatory inputs to the reticulospinal neurons, which, in turn, can activate the spinal circuits underlying locomotion.  
    Also, the input nuclei to the ventral thalamus were labeled following injection of FDA into this nucleus. Labeled cells were found in the olfactory bulb, pallial areas, striatum, preoptic nucleus, hypothalamus, dorsal thalamus, optic tectum, and dorsal isthmic gray. The ventral thalamus, therefore, receives inputs from several different regions in the brain and controls the level of excitability in reticulospinal neurons."  
Brief summary
    "Injection of FDA into the ventral thalamus labeled axonal projections in all reticular nuclei, but no direct projections were found to the spinal cord. "  
    "Extracellular stimulation of the ventral thalamus elicited monosynaptic excitatory postsynaptic potentials (EPSPs), polysynaptic EPSPs, and inhibitory postsynaptic potentials (IPSPs) in reticulospinal neurons in the posterior (prrn) and middle (mrrn) rhombencephalic reticular nuclei. 
    The monosynaptic EPSPs were blocked by the glutamate antagonist kynurenic acid and can be considered glutamatergic". 
    "The ventral thalamus, therefore, receives inputs from several different regions in the brain and controls the level of excitability in reticulospinal neurons."   
    429 Related citations:   
http://www.ncbi.nlm.nih.gov/pubmed/?term=9421142   
     8 Cited by's:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=9421142     
     My comments
1. This is perhaps the reference which most clearly identifies the diencephalic efferent neurons as glutamatergic. 

I have tentatively added a "+" to the thalamic efferent symbol.  Th(GABA) > is now Th(GABA) >+ .  
2.  This reference seems to indicate that the  Ventral Thalamus  projects directly to the Rhombencephalon  and/or the Mesencephalic Locomotor Region in the lamprey.


1997
Role of sensory-evoked NMDA plateau potentials in the initiation of locomotion.   
http://www.ncbi.nlm.nih.gov/pubmed/9353193   
    "Reticulospinal (RS) neurons constitute the main descending motor system of lampreys. 
    This study reports on natural conditions whereby N-methyl-D-aspartate (NMDA)-mediated plateau potentials were elicited and associated with the onset of locomotion.  
    Reticulospinal neurons responded in a linear fashion to mild skin stimulation. With stronger stimuli, large depolarizing plateaus with spiking activity were elicited and were accompanied by swimming movements. Calcium imaging revealed sustained intracellular calcium rise upon sensory stimulation. Blocking NMDA receptors on RS neurons prevented the plateau potentials as well as the associated rise in intracellular calcium.  
    Thus, the activation of NMDA receptors mediates a switch from sensory-reception mode to a motor command mode in RS neurons."  
    160 Related citations:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=9353193   
    14 Cited by's
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=9353193    
    My comments
1.  "Reticulospinal neurons responded in a linear fashion to mild skin stimulation."        
2.  Full-length article free with registration.   
 

1998
Diencephalic and mesencephalic projections to rhombencephalic reticular nuclei in lampreys.   
    See:  Rhombencephalon   .  
    My comment:       
This is another example of behavior which was initiated, not by the Substantia Nigra pars Compacta  (SNc) and not by the rhombocephalon, but by sensory input relayed by interneurones in the rhombencephalon.  This may turn out to be what is actually happening in most cases.   


2000
Stimulation of the mesencephalic locomotor region elicits controlled swimming in semi-intact lampreys.
http://www.ncbi.nlm.nih.gov/pubmed/11069605
     "The role of the mesencephalic locomotor region (MLR) in initiating and controlling the power of swimming was studied in semi-intact preparations of larval and adult sea lampreys. The brain and the rostral portion of the spinal cord were exposed in vitro, while the intact caudal two-thirds of the body swam freely in the Ringer's-containing chamber.  
    Electrical microstimulation (2-10 Hz; 0. 1-5.0 microA) within a small periventricular region in the caudal mesencephalon elicited well-coordinated and controlled swimming that began within a few seconds after the onset of stimulation and lasted throughout the stimulation period. Swimming stopped several seconds after the end of stimulation. The power of swimming, expressed by the strength of the muscle contractions and the frequency and the amplitude of the lateral displacement of the body or tail, increased as the intensity or frequency of the stimulating current were increased. Micro-injection of AMPA, an excitatory amino acid agonist, into the MLR also elicited active swimming.  
    Electrical stimulation of the MLR elicited large EPSPs in reticulospinal neurons (RS) of the middle rhombencephalic reticular nucleus (MRRN), which also displayed rhythmic activity during swimming. The retrograde tracer cobalt-lysine was injected into the MRRN and neurons (dia. 10-20 microm) were labelled in the MLR, indicating that this region projects to the rhombencephalic reticular formation. Taken together, the present results indicate that, as higher vertebrates, lampreys possess a specific mesencephalic region that controls locomotion, and the effects onto the spinal cord are relayed by brainstem RS neurons."
    190 Related citations:
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=11069605
    19 Cited by's:
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=11069605

        
2003 
Nicotinic activation of reticulospinal cells involved in the control of swimming in lampreys. 
http://www.ncbi.nlm.nih.gov/pubmed/12534977  
    "In lampreys as in other vertebrates, brainstem centres play a key role in the initiation and control of locomotion. One such centre, the mesencephalic locomotor region (MLR), was identified physiologically at the mesopontine border. Descending inputs from the MLR are relayed by reticulospinal neurons in the pons and medulla, but the mechanisms by which this is carried out remain unknown.  
    Because previous studies in higher vertebrates and lampreys described cholinergic cells within the MLR region, we investigated the putative role of cholinergic agonists in the MLR-controlled locomotion. The local application of either acetylcholine or nicotine exerted a direct dose-dependent excitation on reticulospinal neurons as well as induced active or fictive locomotion. It also accelerated ongoing fictive locomotion.  
    Choline acetyltransferase-immunoreactive cells were found in the region identified as the MLR of lampreys and nicotinic antagonists depressed, whereas physostigmine enhanced the compound EPSP evoked in reticulospinal neurons by electrical stimulation of this region.  In addition, cholinergic inputs from the MLR to reticulospinal neurons were found to be monosynaptic. When the brainstem was perfused with d-tubocurarine, the induction of swimming by MLR stimulation was depressed, but not prevented, in a semi-intact preparation.   
    Altogether, the results support the hypothesis that cholinergic inputs from the MLR to reticulospinal cells play a substantial role in the initiation and the control of locomotion."    
    199 Related citations:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=12534977  
    6 Cited by's:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=12534977    
  
       
2004
Organization of higher-order brain areas that initiate locomotor activity in larval lamprey.    
http://www.ncbi.nlm.nih.gov/pubmed/15051142 
    "In the lamprey, spinal locomotor activity can be initiated by pharmacological microstimulation in several brain areas: rostrolateral rhombencephalon (RLR); dorsolateral mesencephalon (DLM); ventromedial diencephalon (VMD); and reticular nuclei.  
    During DLM- or VMD-initiated locomotor activity in in vitro brain/spinal cord preparations, application of a solution that focally depressed neuronal activity in reticular nuclei often attenuated or abolished the locomotor rhythm.  
     Electrical microstimulation in the DLM or VMD elicited synaptic responses in reticulospinal (RS) neurons, and close temporal stimulation in both areas evoked responses that summated and could elicit action potentials when neither input alone was sufficient.  
    During RLR-initiated locomotor activity, focal application of a solution that depressed neuronal activity in the DLM or VMD abolished or attenuated the rhythm.  
    These new results suggest that neurons in the RLR project rostrally to locomotor areas in the DLM and VMD. These latter areas then appear to project caudally to RS neurons, which probably integrate the synaptic inputs from both areas and activate the spinal locomotor networks.  
    These pathways are likely to be important components of the brain neural networks for the initiation of locomotion and have parallels to locomotor command systems in higher vertebrates."  

    My comment
This postulates communication from lower to higher levels, which is opposite of my basic assumption. 
    102 Related citations:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=15051142   
    6 Cited by's:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=15051142          
        - Free PMC Article -   
Click on the active link, above. 


2007
Movements and muscle activity initiated by brain locomotor areas in semi-intact preparations from larval lamprey.
http://www.ncbi.nlm.nih.gov/pubmed/17314244
    "In in vitro brain/spinal cord preparations from larval lamprey, locomotor-like ventral root burst activity can be initiated by pharmacological (i.e., "chemical") microstimulation in several brain areas: rostrolateral rhombencephalon (RLR); dorsolateral mesencephalon (DLM); ventromedial diencephalon (VMD); and reticular nuclei. However, the quality and symmetry of rhythmic movements that would result from this in vitro burst activity have not been investigated in detail. In the present study, pharmacological microstimulation was applied to the above brain locomotor areas in semi-intact preparations from larval lamprey. First, bilateral pharmacological microstimulation in the VMD, DLM, or RLR initiated symmetrical swimming movements and coordinated muscle burst activity that were virtually identical to those during free swimming in whole animals. Unilateral microstimulation in these brain areas usually elicited asymmetrical undulatory movements. Second, with synaptic transmission blocked in the brain, bilateral pharmacological microstimulation in parts of the anterior (ARRN), middle (MRRN), or posterior (PRRN) rhombencephalic reticular nucleus also initiated symmetrical swimming movements and muscle burst activity. Stimulation in effective sites in the ARRN or PRRN initiated higher-frequency locomotor movements than stimulation in effective sites in the MRRN. Unilateral stimulation in reticular nuclei elicited asymmetrical rhythmic undulations or uncoordinated movements. The present study is the first to demonstrate in the lamprey that stimulation in higher-order locomotor areas (RLR, VMD, DLM) or reticular nuclei initiates and sustains symmetrical, well-coordinated locomotor movements and muscle activity. Finally, bilateral stimulation was a more physiologically realistic test of the function of these brain areas than unilateral stimulation."  
    197 Related citations: 
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=17314244    
    5 Cited by's: 
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=17314244     
     Free full text: 
http://jn.physiology.org/content/97/5/3229.long   
     

2008
Initiation of Locomotion in Lampreys
http://www.ncbi.nlm.nih.gov/pubmed/17916380    
    "The spinal circuitry underlying the generation of basic locomotor synergies has been described in substantial detail in lampreys and the cellular mechanisms have been identified.  
    The initiation of locomotion, on the other hand, relies on supraspinal networks and the cellular mechanisms involved are only beginning to be understood. This review examines some of the findings relative to the neural mechanisms involved in the initiation of locomotion of lampreys.  
    Locomotion can be elicited by sensory stimulation or by internal cues associated with fundamental needs of the animal such as food seeking, exploration, and mating.  
    We have described mechanisms by which escape swimming is elicited in lampreys in response to mechanical skin stimulation. A rather simple neural connectivity is involved, including sensory and relay neurons, as well as the brainstem rhombencephalic reticulospinal cells, which act as command neurons.  
    We have shown that reticulospinal cells have intrinsic membrane properties that allow them to transform a short duration sensory input into a long-lasting excitatory command that activates the spinal locomotor networks. These mechanisms constitute an important feature for the activation of escape swimming.  
    Other sensory inputs can also elicit locomotion in lampreys. For instance, we have recently shown that olfactory signals evoke sustained depolarizations in reticulospinal neurons and chemical activation of the olfactory bulbs with local injections of glutamate induces fictive locomotion.  
    The mechanisms by which internal cues initiate locomotion are less understood. Our research has focused on one particular locomotor center in the brainstem, the mesencephalic locomotor region (MLR). The MLR is believed to channel inputs from many brain regions to generate goal-directed locomotion. It activates reticulospinal cells to elicit locomotor output in a graded fashion contrary to escape locomotor bouts, which are all-or-none.  
    MLR inputs to reticulospinal cells use both glutamatergic and cholinergic transmission; nicotinic receptors on reticulospinal cells are involved.  
     MLR excitatory inputs to reticulospinal cells in the middle (MRRN) are larger than those in the posterior rhombencephalic reticular nucleus (PRRN). Moreover at low stimulation strength, reticulospinal cells in the MRRN are activated first, whereas those in the PRRN require stronger stimulation strengths. The output from the MLR on one side activates reticulospinal neurons on both sides in a highly symmetrical fashion. This could account for the symmetrical bilateral locomotor output evoked during unilateral stimulation of the MLR in all animal species tested to date.  
    Interestingly, muscarinic receptor activation reduces sensory inputs to reticulospinal neurons and, under natural conditions, the activation of MLR cholinergic neurons will likely reduce sensory inflow. Moreover, exposing the brainstem to muscarinic agonists generates sustained recurring depolarizations in reticulospinal neurons through pre-reticular effects. Cells in the caudal half of the rhombencephalon appear to be involved and we propose that the activation of these muscarinoceptive cells could provide additional excitation to reticulospinal cells when the MLR is activated under natural conditions.  
     One important question relates to sources of inputs to the MLR. We found that substance P excites the MLR, whereas GABA inputs tonically maintain the MLR inhibited and removal of this inhibition initiates locomotion. Other locomotor centers exist such as a region in the ventral thalamus projecting directly to reticulospinal cells. This region, referred to as the diencephalic locomotor region, receives inputs from several areas in the forebrain and is likely important for goal-directed locomotion. In summary, this review focuses on the most recent findings relative to initiation of lamprey locomotion in response to sensory and internal cues in lampreys." 
     953 Related citations:
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=17916380
    28 Cited by's:
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=17916380 
See:  Tonic Inhibition
    Note
The full text is not available online, but, with a little help from a very nice librarian, I was able to download the PDF to my thumb drive. 
    from the full length PDF:  
    "Locomotion can be triggered by sensory inputs as lampreys react vigorously to sensory cues to generate either escape behavior (Fig. 1) or locomotion directed towards a specific target in their environment (for a review see Rossignol et al., 2006)."  
     2006   (Rossignol)  
Dynamic sensorimotor interactions in locomotion.      
http://www.ncbi.nlm.nih.gov/pubmed/16371596  
    152 Related citations
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=16371596  
    122 Cited by's
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=16371596   
    Full Free Text
http://physrev.physiology.org/content/86/1/89.long  
    My comments
1.  The Rossignol reference, above, wasn't very helpful. 
2.  "Other locomotor centers exist such as a region in the ventral thalamus projecting directly to reticulospinal cells. This region, referred to as the diencephalic locomotor region, receives inputs from several areas in the forebrain and is likely important for goal-directed locomotion."   
    a.  The Rossignol Abstract doesn't discuss the neurotransmitters used by the diencephalic locomotor region.
    b.  However, we found that substance P excites the MLR, whereas  GABA inputs tonically maintain the MLR inhibited and removal of this inhibition initiates locomotion.    
    c.  Alternatively, I could do a search for "ventral thalamus" or "diencephalic locomotor region".      


2010
A novel neural substrate for the transformation of olfactory inputs into motor output.
http://www.ncbi.nlm.nih.gov/pubmed/21203583      
    "It is widely recognized that animals respond to odors by generating or modulating specific motor behaviors. These reactions are important for daily activities, reproduction, and survival.  
    In the sea lamprey, mating occurs after ovulated females are attracted to spawning sites by male sex pheromones. The ubiquity and reliability of olfactory-motor behavioral responses in vertebrates suggest tight coupling between the olfactory system and brain areas controlling movements. However, the circuitry and the underlying cellular neural mechanisms remain largely unknown. Using lamprey brain preparations, and electrophysiology, calcium imaging, and tract tracing experiments, we describe the neural substrate responsible for transforming an olfactory input into a locomotor output.  
    We found that olfactory stimulation with naturally occurring odors and pheromones induced large excitatory responses in reticulospinal cells, the command neurons for locomotion. We have also identified the anatomy and physiology of this circuit. The olfactory input was relayed in the medial part of the olfactory bulb, in the posterior tuberculum, in the mesencephalic locomotor region, to finally reach reticulospinal cells in the hindbrain. Activation of this olfactory-motor pathway generated rhythmic ventral root discharges and swimming movements. Our study bridges the gap between behavior and cellular neural mechanisms in vertebrates, identifying a specific subsystem within the CNS, dedicated to producing motor responses to olfactory inputs." 
     113 Related citations:   
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=21203583  
     10 Cited by's
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=21203583   
       - Free PMC Article -     
Click on the active link, above. 


2010   
Descending brain neurons in larval lamprey: spinal projection patterns and initiation of locomotion.
http://www.ncbi.nlm.nih.gov/pubmed/20510243       Free PMC Article   
"Abstract
    In larval lamprey, partial lesions were made in the rostral spinal cord to determine which spinal tracts are important for descending activation of locomotion and to identify descending brain neurons that project in these tracts. In whole animals and in vitro brain/spinal cord preparations, 
     brain-initiated spinal locomotor activity was present when the lateral or intermediate spinal tracts were spared but usually was abolished when the medial tracts were spared.  
    We previously showed that descending brain neurons are located in eleven cell groups, including reticulospinal (RS) neurons in the mesenecephalic reticular nucleus (MRN) as well as the anterior (ARRN), middle (MRRN), and posterior (PRRN) rhombencephalic reticular nuclei. Other descending brain neurons are located in the diencephalic (Di) as well as the anterolateral (ALV), dorsolateral (DLV), and posterolateral (PLV) vagal groups. In the present study, the Mauthner and auxillary Mauthner cells, most neurons in the Di, ALV, DLV, and PLV cell groups, and some neurons in the ARRN and PRRN had crossed descending axons.  
    The majority of neurons projecting in medial spinal tracts included large identified Müller cells and neurons in the Di, MRN, ALV, and DLV. Axons of individual descending brain neurons usually did not switch spinal tracts, have branches in multiple tracts, or cross the midline within the rostral cord.  
    Most neurons that projected in the lateral/intermediate spinal tracts were in the ARRN, MRRN, and PRRN. Thus, output neurons of the locomotor command system are distributed in several reticular nuclei, whose neurons project in relatively wide areas of the cord."     
    105 Related citations:     
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=20510243   
    4 Cited by's: 
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=20510243      
    Full free text: 
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920350/   


2011   
Localization, pharmacology, and organization of brain locomotor areas in larval lamprey.
http://www.ncbi.nlm.nih.gov/pubmed/21081157    Free PMC Article   
    "In larval lamprey, spinal locomotor activity can be initiated by pharmacological microstimulation from the following higher order brain locomotor areas:
    rostrolateral rhombencephalon (RLR); 
    ventromedial diencephalon (VMD); or 
    dorsolateral mesencephalon (DLM).  
In the present study, pharmacological microstimulation with excitatory amino acids (EAAs) or their agonists in the brains of in vitro brain/spinal cord preparations was used to determine the sizes, pharmacology, and organization of these locomotor areas.  
    First, the RLR, DLM and VMD locomotor areas were confined to relatively small areas of the brain, and stimulation as little as 50 μm outside these areas was ineffective or elicited tonic or uncoordinated motor activity.  
    Second, pharmacological stimulation with NMDA, kainate, or AMPA in the VMD or DLM reliably initiated well-coordinated spinal locomotor activity. In the RLR, stimulation with all three ionotropic EAA receptor agonists could initiate spinal locomotor activity, but NMDA or AMPA was more reliable than kainate.  
    Third, with synaptic transmission blocked only in the brain, stimulation in the RLR, VMD, or DLM no longer initiated spinal locomotor activity, suggesting that these locomotor areas do not directly activate spinal locomotor networks.  
    Fourth, following a complete transection at the mesencephalon-rhombencephalon border, stimulation in the RLR no longer initiated spinal motor activity.  
    Thus, the RLR locomotor area does not appear able to initiate spinal locomotor activity by neural circuits confined entirely within the rhombencephalon but requires more rostral neural centers, such as those in the VMD and DLM, as previously proposed."  
    102 Related citations: 
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=21081157   
    Free PMC Article
   



SubC: Initiation of Locomotion in Lampreys 
180917 - 1632 





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