Diencephaloreticular Transmission

Cross references:  ;   Locomotion Sequence      Locomotion Sequence Revision   
Reticulospinal Transmission      Thalamus Tectal Connections    

Rhombencephalon  aka 
Medulla Oblongata  aka  Reticular Activating Sytem      


1998
Diencephalic and mesencephalic projections to rhombencephalic reticular nuclei in lampreys.
http://www.ncbi.nlm.nih.gov/pubmed/9748487  
    "
Behavioral studies in lampreys of the northern genera, Ichthyomyzon, reveal that sensory inputs initiate and modulate locomotion by activation of reticulospinal (RS) neurones, which constitute the primary descending system involved in motor activity. 
The interneurones relaying afferent  
    vestibular,  
    trigeminal,  
    lateral line,  
    cutaneous and  
    proprioceptive inputs  
are localized in the rhombencephalic region of the lamprey brainstem
, unlike the visual inputs that are relayed in the mesencephalic region. 
   
The knowledge of diencephalic-mesencephalic cell distributions that project to the RS neurones is limited. They were isolated by iontophoretically injecting cobalt-lysine in vitro into the middle (MRRN) and posterior (PRRN) rhombencephalic reticular nuclei of Petromyzon marinus and Ichthyomyzon unicuspisFourteen of 31 injections were successful (MRRN, 7; PRRN, 7).   
Cell groups were labeled ipsilateral to the injection site
    in the thalamus (corpi geniculati; pars dorsalis thalami lateralis and medialis; nucleus (n.) subhabenularis lateralis),
    in the epithalamus (n. commissura posteriori) and
    in the pretectum.    
Cell groups were labeled bilaterally
    within the dorsal region along the diencephalic-mesencephalic border (caudal pretectum and rostral tectum opticum),
    in tectum opticum, torus semicircularis, and tegmentum mesencephali.  
There were more backfilled cells from MRRN injections (538-6466 cells) than from PRRN injections (53-553 cells) (MW Rank Sum, p < 0.001). The cell bodies were less than 40 microns long ipsilateral to the injection site, and longer contralaterally. Those greater than 50 microns were backfilled from PRRN injections. The location and organization of the cell groups identified is comparable to that of other vertebrates."  

    My comments:   
1. 
This makes it sound as though behavior is initiated in the rhombencephalon, which is way below the NAC, GP, STN, Th, PTc and Tec
2.  I'm going to have to look at this more carefully, but my initial impression is that the nuclei identified as afferent to the rhombencephalon are not the nuclei which receive the initial sensory input.   
3.  Abstract does not mention neurotransmitters.
    143 Related citations: 
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed&from_uid=9748487   
    I've changed the order of the Related Citations from "Sorted by Link", which is the PubMed default, to "Sorted by Publication Date".  Whenever possible, I prefer to review references in chronological order. 

133<143 1981
Cells of origin of pathways descending to the spinal cord in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata.
http://www.ncbi.nlm.nih.gov/pubmed/7298910  
    "
Cells of origin of diencephalic nuclei, which project to the spinal cord, were observed in the nucleus periventricularis hypothalami and in the thalamus ventralis pars medialis which can in this respect be considered hypothalamic.  
    Descending pathways from mesencephalic structures originate from the interstitial nucleus of the fasciculus longitudinalis medialis, the tectum mesencephali, the nucleus intercollicularis, the tectotegmental junction zone, and from diffusely arranged tegmental neurons.  
    A contralateral rubrospinal pathway could be recognized in Raja, but not in Scyliorhinus.  
    Rhombencephalic cells of origin of pathways descending to the spinal cord were found in all parts of the reticular formation, i.e., the nucleus raphes inferior, the nucleus reticularis inferior, medius, superior, and isthmi, in two vestibular nuclei, and in three nuclei, which have been tentatively indicated as nucleus B, F, and G. Furthermore cells of origin of descending pathways have been found in the nucleus tractus descendens nervi trigemini, in the nucleus funiculi lateralis, and in the nucleus tractus solitarii. The descending pathways of the two species studied have been compared with those of other vertebrates. It is concluded that the basic pattern in the organization of descending pathways to the spinal cord, as proposed by ten Donkelaar ('76) for terrestrial vertebrates, also holds for cartilaginous fishes."      

My comments
1.  Although this paper does not mention the  PTc, in other respects it seems to confirm  the  Th > PTc > Tec > MLR > RAS > SLG  segment of my hypothesized   Locomotion Sequence   .
2.  No mention of neurotransmitters. 

132<143 1982
    The afferent connections of the tectum mesencephali in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata  

http://www.ncbi.nlm.nih.gov/pubmed/7076889  
  
    "
Diencephalic projections to the tectum originate from the thalamus dorsalis pars medialis, the thalamus ventralis pars lateralis, the nucleus medius infundibuli, and the pretectal area."  
    See:  Thalamus Tectal Connections   for full Abstract and Related citations .  
No mention of neurotransmitters.  
  

119<143 1989
Origins of the descending spinal projections in petromyzontid and myxinoid agnathans.
http://www.ncbi.nlm.nih.gov/pubmed/2925902  
    "
The origins of the descending spinal pathways ... in lampreys, the majority of HRP-labeled cells were located along the length of the brainstem reticular formation in the inferior, middle, and superior reticular nuclei of the medulla, mesencephalic tegmentum, and nucleus of the medial longitudinal fasciculus."    
    "
The existence of reticulospinal and possible vestibulo-, trigemino-, and solitary spinal projections ..."  
My comments
1.  This reference confirms the MLR > RAS > SLG  segment of my hypothesized   Locomotion Sequence  and, in addition suggests "possible vestibulo-, trigemino-, and solitary spinal projections".    
2.  No mention of neurotransmitters. 


109<143  1994 
Rostro-caudal distribution of reticulospinal projections from different brainstem nuclei in the lamprey
http://www.ncbi.nlm.nih.gov/pubmed/7882039  
    "
The reticulospinal (RS) system in the lamprey is responsible for the control of locomotion, postural corrections and steering. To perform these functions, the RS system has to affect different muscular compartments along the body axis selectively. In this study, the possibility that RS neurones in different nuclei may project to different parts of the spinal cord, was investigated. The rostro-caudal extent of single RS axons was defined by stimulating them antidromically while recording from their cell body.  
    All recorded mesencephalic RS neurones projected to the caudal tip of the spinal cord. Of the rhombencephalic RS neurones, 26% of the recorded neurones did not reach the caudalmost fourth of the spinal cord and this proportion varied between the anterior (18%), middle (17%) and posterior (36%) rhombencephalic reticular nuclei. For these RS axons, the level of termination covered the whole rostro-caudal extent of the spinal cord. No correlation was found between the length of an axon and its conduction velocity or between the length of an axon and the rostro-caudal position of its cell body in the nuclei."  
My comments
1.  Technically speaking, this reference doesn't really consider thalamic projections since it doesn't consider anything above the MLR.     
2.  No mention of neurotransmitters. 


92<143 
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   
   

    "Injection of FDA into the ventral thalamus labeled axonal projections in all reticular nuclei, but no direct projections were found to the spinal cord.
My comments
1.  This seems to imply Th > RAS without any intervening Th > PTec or Th > Tec.     
2.  No mention of neurotransmitters. 
3.  See:  Initiation of Locomotion in Lampreys for full Abstract, Related citations and Cited by's. 


86<143    1998 
Electrophysiological and neuropharmacological study of tectoreticular pathways in lampreys.  
    See:  Tectospinal Tract  for full Abstract and Related citations . 


68<143    2000   
Activity of reticulospinal neurons during locomotion in the freely behaving lamprey.  
    "
In conclusion, different aspects of locomotor activity-initiation and termination, vigor of locomotion, steering and equilibrium control-are well reflected in the mass activity of the larger RS neurons."
    See:    Activity of Reticulospinal Neurons During Locomotion   for full Abstract, Related citations, Cited by's, and a full free text. 

 
    

61<143    2000
Stimulation of the mesencephalic locomotor region elicits controlled swimming in semi-intact lampreys.  
    "
Electrical stimulation of the MLR elicited large EPSPs in reticulospinal neurons (RS) of the middle rhombencephalic reticular nucleus (MRRN)"  
My comment
    This confirms the MLR > RAS   segment of my hypothesized   Locomotion Sequence  .  
    See:    Initiation of Locomotion in Lampreys   for full Abstract, Related citations and Cited by's.   


41<143      2003  
Differential contribution of reticulospinal cells to the control of locomotion induced by the mesencephalic locomotor region.  
    See:  Activity of Reticulospinal Neurons During Locomotion  .  

 

32<143 2005
The trigeminal sensory relay to reticulospinal neurones in lampreys
http://www.ncbi.nlm.nih.gov/pubmed/15708494  
    "
This study was carried out to identify lamprey neurones relaying trigeminal sensory inputs to reticulospinal cells.  
    Double labeling with fluorescent tracers was used in vitro. Fluorescein-conjugated dextran amines were applied to the proximal stump of the cut trigeminal nerve on both sides, and Texas Red-conjugated dextran amines were injected unilaterally in the middle (MRRN) or the posterior (PRRN) rhombencephalic reticular nuclei. Texas Red retrogradely labeled cells were found ipsi- and contralateral to each injection. Any of these cells with the soma or at least a major dendrite among the fluorescein-labeled trigeminal afferent axons was considered a candidate relay cell. Of these two possibilities, only cells with their soma among the fluorescein-labeled trigeminal afferents were found.  
    The candidate relay cells projecting to the MRRN were mostly clustered at the caudal vestibular nerve level within the trigeminal descending tract, whereas the majority of those projecting to the PRRN were located more caudally. The diameter of candidate relay cells ranged from 9.2 to 24.6 mum and 9.2 to 46.1 mum, after MRRN and PRRN injections, respectively.  
    A possible relay function for these cells was tested with electrophysiological experiments. The intracellular responses to trigeminal nerve stimulation were recorded in reticulospinal cells under control conditions and after  
    ejections of a combination of glutamate ionotropic receptor antagonists over the candidate relay cells in small areas along the sulcus limitans. The synaptic responses elicited in MRRN reticulospinal cells were maximally depressed when ejections were made at the level of the vestibular nerve, in accord with the anatomical data. The synaptic responses in PRRN reticulospinal cells showed maximal depression when ejections were made slightly more caudally.  
    Altogether, these results suggest that cells located within the trigeminal descending tract and projecting to reticular nuclei are likely to be the sensory trigeminal relays to reticulospinal neurones in lampreys."  
My comments
1.  Although I don't remember seeing it stated explicitly, I'm beginning to think that the label "reticulospinal cell" might be another way of identifying cells in the MRRN and PRRN.     
2.  Mentions "glutamate ionotropic receptor antagonists". 


29<143   2006
Neuroanatomical approaches of the tectum-reticular pathways and immunohistochemical evidence for serotonin-positive perikarya on neuronal substrate...
http://www.ncbi.nlm.nih.gov/pubmed/16303128  

     "Deep layers of the superior colliculus, the dorsal periaqueductal gray matter and the inferior colliculus are midbrain structures involved in the generation of defensive behavior and fear-induced anti-nociception.   Local injections of the GABA(A) antagonist bicuculline into these structures have been used to produce this defense reaction.  
    Serotonin is thought to be the main neurotransmitter to modulate such defense reaction in mammals. This study is the first attempt to employ immunohistochemical techniques to locate serotonergic cells in the same midbrain sites from where defense reaction is evoked by chemical stimulation with bicuculline.  
    The blockade of GABA(A) receptors in the neural substrates of the dorsal mesencephalon was followed by vigorous defensive reactions and increased nociceptive thresholds.  
    Light microscopy immunocytochemistry with streptavidin method was used for the localization of the putative cells of defensive behavior with antibodies to serotonin in the rat's midbrain. Neurons positive to serotonin were found in the midbrain sites where defensive reactions were evoked by microinjection of bicuculline.  
    Serotonin was localized to somata and projections of the neural networks of the mesencephalic tectum. Immunohistochemical studies showed that the sites in which neuronal perikarya positive to serotonin were identified in intermediate and deep layers of the superior colliculus, and in the dorsal and ventral columns of the periaqueductal gray matter are the same which were activated during the generation of defense behaviors, such as alertness, freezing, and escape reactions, induced by bicuculline.  
    These findings support the contention that serotonin and GABAergic neurons may act in concert in the modulation of defense reaction in the midbrain tectum. Our neuroanatomical findings indicate a direct neural pathway connecting the dorsal midbrain and monoaminergic nuclei of the descending pain inhibitory system, with profuse synaptic terminals mainly in the pontine reticular formation, gigantocellularis nucleus, and nucleus raphe magnus. The midbrain tectum-gigantocellularis complex and midbrain tectum-nucleus raphe magnus neural pathways may provide an alternative output allowing the organization of the fear-induced anti-nociception by mesencephalic networks."  
Important point
     "Deep layers of the superior colliculus, the dorsal periaqueductal gray matter and the inferior colliculus are midbrain structures involved in the generation of defensive behavior and fear-induced anti-nociception.   Local injections of the GABA(A) antagonist bicuculline into these structures have been used to produce this defense reaction."      


23<143    2006
Afferents of the lamprey optic tectum with special reference to the GABA input: combined tracing and immunohistochemical study.  
    See:  Lamprey GABA  .   
 

21<143  
2007
Afferent connections of the optic tectum in lampreys: an experimental study  
    See: Tectum  for full Abstract and Related citations.   


19<143    2007 

Descending GABAergic projections to the mesencephalic locomotor region in the lamprey Petromyzon marinus.     
    See:   GABA/Glycine Inhibition  .     


18<143 
2007
Movements and muscle activity initiated by brain locomotor areas in semi-intact preparations from larval lamprey.  

    See:  Initiation of Locomotion in Lampreys 


17<143   
2007
GABA distribution in lamprey is phylogenetically conserved. 
    See:   Lamprey GABA  .   


13<143 
2008
Initiation of Locomotion in Lampreys 
   
See:  Initiation of Locomotion in Lampreys 


11<143 
2008
Afferent and efferent connections of the mesencephalic reticular formation in goldfish.
 
    See:  Mesencephalic Locomotor Region  .   


8<143 2008
Diencephalic locomotor region in the lamprey--afferents and efferent control.
http://www.ncbi.nlm.nih.gov/pubmed/18596192  
    "
In vertebrates, locomotion can be initiated by stimulation of the diencephalic locomotor region (DLR). Little is known of the different forebrain regions that provide input to the neurons in DLR. 
    In the lamprey, it had been shown previously that DLR provides monosynaptic input to reticulospinal neurons, which in turn elicit rhythmic ventral root activity at the spinal level. To show that actual locomotor movements are produced from DLR, we use a semi-intact preparation in which the brain stem is exposed and the head fixed, while the body is left to generate actual swimming movements. DLR stimulation induced symmetric locomotor movements with an undulatory wave transmitted along the body.  
    To explore if DLR is under tonic GABAergic input under resting conditions, as in mammals, GABAergic antagonists and agonists were locally administered into DLR. Injections of GABA agonists inhibited locomotion, whereas GABA antagonists facilitated the induction of locomotion. These findings suggest that GABAergic projections provide tonic inhibition that once turned off can release locomotion.  
     Double-labeling experiments were carried out to identify GABAergic projections to the DLR. Populations of GABAergic projection neurons to DLR originated in the caudoventral portion of the medial pallium, the lateral and dorsal pallium, and the striatal area. These different GABAergic projection neurons, which also project to other brain stem motor centers, may represent the basal ganglia output to DLR. Moreover, electrical stimulation of striatum induced long-lasting plateau potentials in reticulospinal cells and associated locomotor episodes dependent on DLR being intact, suggesting that striatum may act via the basal ganglia output identified here." 
Important highlights
    "
DLR provides monosynaptic input to reticulospinal neurons, which in turn elicit rhythmic ventral root activity at the spinal level."         
    "
Injections of GABA agonists inhibited locomotion, whereas GABA antagonists facilitated the induction of locomotion. These findings suggest that GABAergic projections provide tonic inhibition that once turned off can release locomotion."  
    12 Cited by's
    Free Full Text:   
http://jn.physiology.org/content/100/3/1343.long   


3<143 2010
Descending brain neurons in larval lamprey: spinal projection patterns and initiation of locomotion.
    See:  Initiation of Locomotion in Lampreys   for full Abstract, Related citations, Cited by's and full free text. 


1<143 2011
Inhibitory descending rhombencephalic projections in larval sea lamprey.  
    See:  GABA/Glycine Inhibition  for full Abstract and Related citations. 
  


 

 

 

      
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