Reticulospinal Transmission

Note:  I've put the following references in chronological order and specified the searches which found them when that is known.   However, not all the searches used the same search terms, and I no longer remember what some of them were.

"reticulospinal transmission" - 150 PubMed references:   

1973   (Goog)            
On the Descending Control of the Lumbosacral Spinal Cord from the Mesencephalic Locomotor Region
No PubMed Abstract:   
but there is a Google Abstract:          
    "The results would be explained if the noradrenergic reticulospinal system was activated from the mesencephalic locomotor region."  
    See:    Mesencephalic Locomotor Region   .  

1974 142<150
Synaptic interactions of reticulospinal neurons and nerve cells in the spinal cord of the sea lamprey.
No PubMed Abstract:
but there is a Google Abstract:

    "The reticulospinal system is the major descending pathway from the brain to the spinal cord in the sea lamprey, Petromyzon marinus. In order to determine the synaptic connections of this system and to gain a better understanding of its functions, individual cell bodies and axons of identified reticulospinal neurons were stimulated intracellularly while recording from spinal interneurons and motoneurons.

  • 1
    Stimulation of reticulospinal axons of the bulbar and vagal groups produced unitary composite EPSP's in lateral cells. Both components of these EPSP's followed repetitive presynaptic action potentials one-to-one at constant short latencies. The first component was due to electrical coupling between the cell and axon. The second component was due to chemical transmission because it was eliminated after extracellular Ca was replaced with Mg and because it changed in amplitude during repeated stimulation. Evidence is presented that the second component, as well as the first, is monosynaptic.
  • 2
    Both fast and slow motoneurons to myotomal muscle received a predominantly electrical synapse from the Müller axon I1. They also exhibited composite EPSP's after stimulation of M1, M3, some bulbar cells, and the Mauthner cell. Stimulation of ventral roots produced depolarizations in Müller axons which excited motoneurons. Polysynaptic EPSP's were observed in a fin motoneuron after stimulation of the contralateral axon M3 or I1.
  • 3
    Some edge cells exhibited a composite EPSP after stimulation of the bursting axon I2.
  • 4
    Morphologically mixed synapses with both chemical and electrical junctions were observed between Müller axons and unidentified dendrites.
  • 5
    The cells of origin of the bursting axons were the pair I2. Stimulation of these axons in situ produced either no movements or weak fin movements. No synaptic potentials were observed in motoneurons in the cord or in bulbar cells in the brain after stimulation of I2.
  • 6
    Intracellular stimulation of giant interneurons produced EPSP's in one pair of bulbar cells.
  • 7
    The conclusions drawn from this and the preceding study are as follows: (a) Connections of identified neurons in the lamprey are specific but do not always occur. (b) The majority of synapses from large axons to identified cells utilize dual electrical and chemical transmission. (c) Most unitary EPSP's are subthreshold. Thus, other sources of excitation, especially from smaller unidentified neurons, are required for activity.   
My comments
"The first component was due to electrical coupling between the cell and axon. The second component was due to chemical transmission ..."  I'm surprised.  I had no idea that lampries used electronic synapses. 
2.  "
Both fast and slow motoneurons to myotomal muscle ..."  Although this is neurons rather than muscles, it  sounds like:   Fast vs. Slow Twitch Muscles   .    
3.  "
Morphologically mixed synapses with both chemical and electrical junctions were observed ...".  Again, I'm surprised.  

1974    141<150
Characteristics of fast and slow corticobulbar fibre projections to reticulospinal neurones. - PubMed
No PubMed Abstract:
but there is a Google Abstract     
"The brain stem reticular formation is an important structure transmitting extrapyramidal influences to the spinal cord. This transmission is realized predominantly through pontine reticular nuclei and nucleus reticularis gigantocellularis of the medulla; axons of many of the neurones of these nuclei project in a descending direction."   
My comment
     The statement, "
transmission is realized predominantly through pontine reticular nuclei and nucleus reticularis gigantocellularis", is very important to me.  I need to follow this thread.   
    See:  Lamprey Nervous System  and   Fast vs. Slow Twitch Muscles .    
Although there was no PubMed Abstract, there were 120 PubMed Related citations   

1976    137<15
Projections of reticular neurones to dorsal regions of the spinal cord in the cat. - PubMed
    "Approximately 34% of reticulospinal neurones in the medulla, and 28% in the pons, were found to project to dorsal regions of the cord"
46 Related Citations:  

Physiological and anatomical characteristics of reticulospinal neurones in lamprey.    
from the Abstract: 
    "1. Intracellular records were obtained from giant reticulospinal cells (Müller cells) in the brain of adult lamprey. ... 
    2. Individual spontaneous excitatory and inhibitory synaptic potentials (e.p.s.p.s and i.p.s.p.s) were observed, as well as occasional high frequency bursts of excitatory potentials. Much of the spontaneous synaptic activity could be eliminated by elevating the Ca(2+) concentration in the bathing solution to 10-15 mM, suggesting that the synaptic potentials were due to spike activity in elements presynaptic to Müller cells. 
    3. Electrical stimulation of cranial nerves produced synaptic responses in Müller cells. Ipsilateral vestibular nerve stimulation produced i.p.s.p.s; contralateral stimulation, e.p.s.p.s. Stimulation of either optic nerve produced mixed synaptic responses with e.p.s.p.s dominating in cells with large resting potentials. Trigeminal nerve stimulation produced mixed responses. Olfactory nerve stimulation produced excitation. Spinal cord stimulation produced e.p.s.p.s and i.p.s.p.s, the dominant effect being inhibition. 
    4. In favourable preparations strong electrical stimulation of cranial nerves produced after disharges in Müller cells, lasting from a few seconds after stimulation of the olfactory and vestibular nerves to as long as several minutes after optic, trigeminal or spinal cord stimulation. 
    5. Natural stimulation of tactile, visual and vestibular receptors resulted in synaptic responses similar to those produced by electrical stimulation of the cranial nerves. Fish odour applied to the olfactory mucosa produced no response. 
    6. Iontophoretic application of L-glutamate to Müller cells produced depolarization accompanied by a decrease in input resistance. In addition, glutamate produced bursts of inhibitory and excitatory synaptic potentials, presumably by depolarizing excitatory or inhibitory nerve terminals or nearby cell bodies. 
    7. Iontophoretic application of gamma-aminobutyric acid (GABA) resulted in a slight hyperpolarization, accompanied by a large reduction in input resistance. The reversal point both of the hyperpolarizations and of the spontaneous inhibitory post-synaptic potentials was about 6 mV greater than the resting potential. 
    8. There were two types of synaptic ending on Müller cell bodies, one type containing round vesicles and the other containing ellipsoidal vesicles. These terminals were intermixed over the surface of the cell bodies and dendrites with no readily apparent segregation. 
    9. Intracellular records from the spinal axons of Müller cells during electrical stimulation of cranial nerves and spinal cord showed, in addition to the normal propagating action potential activity which normally originates in the cell bodies, depolarizing, hyperpolarizing and biphasic evoked potentials. These membrane responses were grossly similar in appearance to synaptic potentials except that the large depolarizing potentials had unusually long decay times. The physiological basis of these potentials remains unclear. 
    10. Electron microscopic examination showed very few synaptic endings afferent to Müller axons, a finding in contrast to the abundance of synaptic-like potentials recorded. However, the occasional synapses afferent to Müller axons were invariably located near an efferent synaptic region of the axon itself. This raises the possibility that a very limited number of synaptic regions of Müller axons may be subject to presynaptic modulation of transmitter release. 
    11. The observations reported here support the idea that Müller cells in lamprey are an important motor outflow from the brain and serve to coordinate the lamprey's trunk responses to external sensory stimulation.   
My comments
1.  Since we humans don't have Muller cells, I'm not sure how applicable this is to us. 
2.  The similarity between this reference and the one preceeding it, #5503275, probably reflects the fact that they share the authorship of  Wickelgren WO
     579 Related citations:    
     12 Cited by's:
     Free PMC Article           
Click on the active link, above. 

1977  136<15
Transmission of reticulofugal activity through the ventromedial group of propriospinal neurons in cats
(in Russian)
Responses of propriospinal interneurons localized in the ventromedial regions of the cat lumbar cord to the reticulospinal tract stimulation were studied. Monosynaptic excitatory action usually accompanied by di- and polysynaptic components was found in most units. Strong single stimuli were able to evoke discharges only in some cells, while temporal summation was necessary in many others. Excitation of neurons was followed by a short postactivation inhibition limiting the maximal discharge frequency."      
91 Related citations   

1977    135<150
Synaptic effects induced in lamprey motor neurons by direct stimulation of individual presynaptic fibers
Parallel intracellular recording from giant reticulospinal axons and target motoneurons of the lamprey (Lampetra fluviatilis) revealed unitary synaptic actions produced in the post-synaptic membrane by direct stimulation of individual presynaptic fibres. It is shown that monosynaptic reticulomotoneuronal EPSPs contain both electrical and chemical components which have different synaptic delay, time course, amplitude, sensitivity to Cadeficit and operating characterisitcs. A single motoneuron may receive direct electrotonic inputs from several giant axons. Individual giant axons may affect segmental motoneurons not only via monosynaptic connections but also via additional synaptic relays."
111 Related citations:

1977  134<150

Electrotonic and chemical EPSPs in lamprey motor neurons following stimulation   
In experiments carried out on the isolated spinal cord of the lamprey (Lampetra fluviatilis) post-synaptic responses produced in spinal motoneurons by stimulation of the descending tract and dorsal roots were investigated by means of the intracellular recording technique. It is found that, in addition to giant reticulospinal (Müller's) axons, many other descending fibres as well as dorsal root afferents establish synaptic linkage with both chemical and electrical mode of transmission as revealed by their sensitivity to calcium-deficient and magnesium-rich perfusing solutions. Complex electrotonic EPSPs could have a very fast time course characteristic for the elementary responses but could also produce slow depolarization of the post-synaptic membrane, thus suggesting an integrative function of electrical synapses."  
107 Related citations       

1977  132<150

Interneuronal synapses with electrical and chemical mechanisms of transmission and the evolution of the central nervous system 
It becomes increasingly evident that not only chemical but also electrotonic synapses are characteristic feature of the vertebrate brain.
    See:  Motor Neuron Evolution  for full Abstract and Related citations

1980   123<150

Excitatory postsynaptic potentials in motor neurons of rats upon stimulation of individual reticulospinal neurons
    "Unit reticulo-motoneuronal EPSPs evoked by extra -- or intracellular stimulation of reticulo-spinal neurons were recorded intracellularly from rat lumbar motoneurons. Reticular neurons with fast conducting axons revealed higher probability of direct effect on motoneurons. Terminals of single reticular neurons to different motoneurons were shown to be widely distributed. Analysis of the time course of average unit EPSPs suggests proximal to soma location of some reticulo-motoneuronal synapses. Amplitude-frequency histograms of the unit EPSPs could be fitted in most cases by Poisson's or binominal distribution, suggesting the quantal nature of transmitter release."
    244 Related citations:

1981  118<150

Descending projections to the cervical spinal cord in the developing kitten. - PubMed
    "The distribution of neurons filled by retrograde axonal transport of horseradish peroxidase from the cervical enlargement is described in kittens prior to and following the time of appearance of mature alpha-motoneuron responses to motor cortical stimulation (at 107-111 days gestational age; about 41 days postnatally). Cortex and brainstem reconstructions of the distributions of filled neurons demonstrate a well-defined, discrete projection from cortical area 4 to spinal cord segments C3 to C8, both in mature and immature (20 and 24 days postnatal) animals. In addition, appropriate rubrospinal, reticulospinal and vestibulospinal projections were present at all ages studied."
    148 Related citations:
and 1 Cited by.
    Key Point
"kittens ...
rubrospinal, reticulospinal and vestibulospinal projections were present at all ages"     

128<144    1982 
Brain neurons which project to the spinal cord in young larvae of the zebrafish   
    "A small number of brain neurons project to caudal levels of the spinal cord in the larva of the teleost Brachydanio rerio." 
    "They were located within three regions of the brainstem: the midbrain nucleus of origin of the medial longitudinal fascicle (mlf), the hindbrain reticular formation, and the hindbrain vestibular nucleus."
    "The observed distribution of labeled reticulospinal cells is similar to that previously described for large reticular cells in adult teleosts and to the system of identified Mauthner and Müller cells in the lamprey."      
    23 Cited by's:  
    from:  Rhombencephalon

123<144    1984 
Early development of descending pathways from the brain stem to the spinal cord in Xenopus laevis   
The observations demonstrate that already very early in development reticulospinal fibers and, somewhat later, Mauthner cell axons and vestibulospinal fibers innervate the spinal cord."   
    from:  Rhombencephalon

1983  115<150

Convergence on reticulospinal neurons mediating contralateral pyramidal disynaptic EPSPs to neck motoneurons.
    "Convergence upon reticulospinal neurons which mediate disynaptic, contralateral pyramidal EPSPs to neck motoneurons has been examined in cats with contralateral pyramidal transection at the obex. Conditioning stimuli in the contralateral tectum and ipsilateral mesencephalic tegmentum produced monosynaptic facilitation of the disynaptic pyramidal EPSP, whereas facilitation evoked from the ipsilateral pyramid showed a disynaptic time course. These results show that contralateral pyramidal, tectal and ipsilateral tegmental fibers converge onto common reticulospinal neurons which have direct excitatory connections with neck motoneurons."
    362 Related citations: 
and 2 Cited by's.  
    Key Point
contralateral pyramidal, tectal and ipsilateral tegmental fibers converge onto common reticulospinal neurons which have direct excitatory connections"  

Early development of descending pathways from the brain stem to the spinal cord in Xenopus laevis
    "The observations demonstrate that already very early in development reticulospinal fibers and, somewhat later, Mauthner cell axons and vestibulospinal fibers innervate the spinal cord."
    282 Related citations:
    and 5 Cited by's.  

A spinal projection of 5-hydroxytryptamine neurons in the lamprey brainstem; evidence from combined retrograde tracing and immunohistochemistry.
    "To investigate whether there is a descending contribution to the spinal 5-hydroxytryptamine (5-HT) innervation in the lamprey, a primitive vertebrate, a study using retrograde transport of the fluorescent tracer Fast blue combined with 5-HT immunohistochemistry was conducted. Two to 4 weeks after an injection of Fast blue into the rostral spinal cord, retrogradely labelled cells were seen throughout the brainstem. Two groups of these cells, one within the posterior reticular nucleus of the rhombencephalon and another rostral to the trigeminal motor nucleus, were labelled after incubation with 5-HT antiserum. These findings suggest that in addition to the well-described local intraspinal 5-HT system, there is also, as in higher vertebrates, a descending 5-HT projection from the brainstem which extends at least 20 segments into the spinal cord."
    124 Related citations:
    and 2 Cited by's

1987 111<150 
Efficiency of electrical transmission in reticulomotoneuronal synapses of lamprey spinal cord.    
electrical transmission is involved in functioning of the lamprey nervous system"   
    See:   Lamprey Neurotransmitters   .

1988  107<150 
Excitatory amino acid-evoked membrane currents and excitatory synaptic transmission in lamprey reticulospinal neurons.  
Application of glutamate evoked depolarizations associated with a decrease in input resistance."  , but I think the experimental substances were bath-applied and therefore neuromodulators and not neurotransmitters.   
    See:   Lamprey Neurotransmitters   .  

Reticulospinal neurons in lamprey: transmitters, synaptic interactions and their role during locomotion
    No PubMed Abstract
     but full length, 28-page PDF with diagrams:   
The mesencephalic and rhombencephalic reticular formation in lamprey have been shown to contain several classes of descending neurons with different morphologies and putative neurotransmitters."  
    "The vestibular nerves also activate a direct vestibulospinal projection to the rostral segments of the spinal cord." 

1989  106<150 
Further evidence for excitatory amino acid transmission in lamprey reticulospinal neurons: selective retrograde labeling with (3H)D-aspartate.           
"lamprey reticulospinal neurons utilize excitatory amino acid transmission."
    See:   Lamprey Neurotransmitters   .  

1989  105<150 
Monosynaptic excitatory amino acid transmission from the posterior rhombencephalic reticular nucleus to spinal neurons involved in the control of locomotion in lamprey.  
   "1. The reticulospinal neurons in the lamprey posterior rhombencephalic reticular nucleus (PRRN) and their projections to different types of spinal neurons have been investigated by the use of simultaneous paired intracellular recordings from one pre- and one postsynaptic cell. PRRN is of particular importance for the initiation of locomotion.
    2. Intracellular stimulation of single PRRN neurons produced monosynaptic excitatory postsynaptic potentials (EPSPs) in simultaneously recorded motoneurons and spinal premotor interneurons of both the excitatory and inhibitory type. Individual PRRN neurons produced EPSPs in several different types of target cells, as revealed by signal averaging. Each single PRRN neuron had extensive monosynaptic connections to approximately 73% of the motoneuronal population. Conversely, several PRRN neurons converge on individual spinal neurons. ...
    3. The EPSPs produced by reticulospinal cells were composed of either exclusively chemical, exclusively electrical, or mixed chemical and electrical components. The electrical EPSPs remained when the ordinary physiological solution was substituted for one without Ca2+ but with Mn2+. The chemical component of the EPSPs was always depressed when a broad-spectrum excitatory amino acid (EAA) antagonist, such as kynurenic acid, was applied, suggesting that the chemical component was because of EAA transmission. The chemical EPSP could have two components, one late, suppressed by N-methyl-D-aspartate (NMDA) antagonists, and one early because of activation of kainate/quisqualate receptors.  
    4. Three-dimensional reconstructions of Lucifer yellow-filled PRRN neurons were performed with a confocal laser scanning microscope. PRRN neurons producing monosynaptic excitatory amino acid EPSPs were found to have a fusiform cell body located near the surface of the fourth ventricle and an extensive fanlike dendritic tree extending to the ventral and lateral margin of the brain stem within the basal plate. The axons descend in the lateral funiculi of the spinal cord.  
    5. PRRN neurons utilizing EAA transmission are active during fictive locomotion. They presumably initiate and reinforce ongoing spinal locomotor activity by monosynaptically increasing the general excitability of the spinal premotor interneurons of the spinal locomotor networks by means of their extensive divergent and convergent monosynaptic connections.
My comments:   
1.  Although this study used "
simultaneous paired intracellular recordings from one pre- and one postsynaptic cell", the experimenters also manipulated the bath solution.         
2.  Nevertheless, the "simultaneous paired intracellular recordings from one pre- and one postsynaptic cell" seem to indicate that "Intracellular stimulation of single PRRN neurons produced monosynaptic excitatory postsynaptic potentials (EPSPs) in simultaneously recorded motoneurons and spinal premotor interneurons" . 
3.  The evidence for a "chemical component" to the EPSPs is from bath-applied neuromodulators. 
4.  This is the first mention of the "posterior rhombencephalic reticular nucleus" . 
" Intracellular stimulation of single PRRN neurons produced monosynaptic excitatory postsynaptic potentials (EPSPs) in simultaneously recorded motoneurons and spinal premotor interneurons of both the excitatory and inhibitory type."  
paired intracellular recordings" rather than neurotransmitters or receptors. 
    242 Related citations:  
    6 Cited by's   

    See:   Lamprey Neurotransmitters   .  

Origins of the descending spinal projections in petromyzontid and myxinoid agnathans.   
    The origins of the descending spinal pathways in sea lampreys (Petromyzon marinus), silver lampreys (Ichthyomyzon unicuspis), and Pacific hagfish (Eptatretus stouti) were identified by the retrograde transport of horseradish peroxidase (HRP) placed in the rostral spinal cord.  
    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. Labeled reticular cells included the Mauthner and Müller cells. Horseradish-peroxidase-filled cells were also present in the descending trigeminal tract, intermediate and posterior octavomotor nuclei, and a diencephalic cell group, the nucleus of the posterior tubercle.  
    As in lampreys, the reticular formation of the Pacific hagfish was the largest source of descending afferents to the spinal cord. Labeled cells were found in the dorsolateral and ventromedial reticular nuclei, the dorsal tegmentum at the juncture of the medulla and midbrain, and the nucleus of the medial longitudinal fasciculus. Additional medullary cells projecting to the cord were located in the perivagal nucleus, the central gray, and the anterior and posterior magnocellular octavolateralis nuclei.  
    The existence of reticulospinal and possible vestibulo-, trigemino-, and solitary spinal projections in lampreys and hagfishes and the wide distribution of these pathways in jawed vertebrates suggest that they evolved in the common ancestor of gnathostomes and both groups of jawless fishes. However, descending spinal pathways from the cerebellum, red nucleus, and telencephalon appear to be gnathostome characters."

    4 Cited by's  

Searching PubMed for "spinal locomotor generator reticular" yielded 5 references.       
     Only 1 of the 5 is considered, below.  Although it's in Russian, the Related citations might be useful. 
[The brain stem pathways of locomotion initiation].  [Article in Russian] 
    "The data about structural organization, connections and different ways of activation of the brain stem locomotor regions are offered in the review. The specificity of the locomotor regions and pathways of their influence on the spinal locomotor generator is discussed, the role of the reticular formation is elucidated. It is suggested that side by side with the multilevel system of the locomotion initiation, which has an output on the spinal cord via medial reticular formation, nonspecific afferent activation of the brain stem is also very significant."  
119 Related citations:    

1992  102<150 
Phasic modulation of transmission from vestibular inputs to reticulospinal neurons during fictive locomotion in lampreys.  
phasic modulation of vestibular transmission is not due to changes in the membrane properties of the reticulospinal cell but is produced at a pre-reticular level"  
    See:   Activity of Reticulospinal Neurons During Locomotion   . 

1994  93<150

Giant neurons in the rat reticular formation: a sensorimotor interface in the elementary acoustic startle circuit?
   Full length PDF:

Rostro-caudal distribution of reticulospinal projections from different brainstem nuclei in the lamprey.    
    "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."
    159 Related citations:  

1995  87<150 
Reticulospinal neurones provide monosynaptic glycinergic inhibition of spinal neurones in lamprey.  
    "In lamprey, distinct groups of reticulospinal neurones utilize different neurotransmitters such as glutamate or serotonin. The present study demonstrates that a group of reticulospinal neurones inhibit their target neurones by an action on glycine receptors. 
     See:  Inhibition of Locomotion in Lampreys  .   

1995  85<150 
Trigeminal inputs to reticulospinal neurones in lampreys are mediated by excitatory and inhibitory amino acids.   
    See:   Lamprey Neurotransmitters   .      

1996 81<150
Visual potentiation of vestibular responses in lamprey reticulospinal neurons. - PubMed
    "The middle rhombencephalic reticular nucleus (MRRN) is considered a main nucleus for the control of roll orientation in lampreys. Practically all MRRN neurons receive vestibular and visual input and project to the spinal cord."
    1189 Related citations:
    and two Cited by's.

1997  76<150 
Role of sensory-evoked NMDA plateau potentials in the initiation of locomotion.   
Reticulospinal (RS) neurons constitute the main descending motor system of lampreys." 

1998  74<150 
Differential effects of the reticulospinal system on locomotion in lamprey.    
the proportion of RS neurons with different influences on the spinal locomotor network differs significantly among different parts of the reticular formation of the lamprey"  
    See:  Lamprey Locomotion .     

From: Searching PubMed for "thalamus tectal connections" identified 60 references: 

13<60    2001
Neural modulation of visuomotor functions underlying prey-catching behaviour in anurans: perception, attention, motor performance, learning. Only abstract available online, but I was able to obtain the full paper through the library.   

I was particularly attracted to this article because of it's discussion of the "retino-tecto/tegmento-bulbar/spinal serial processing streams".  This phrase is an accurate description of how I conceptualize locomotion.     

    Please see: 
Locomotion Sequence  and  Anurian Prey Catching  . 

Comparison of the motor effects of individual vestibulo- and reticulospinal neurons on dorsal and ventral myotomes in lamprey.
    "In the lamprey (a lower vertebrate), motor commands from the brain to the spinal cord are transmitted through the reticulospinal (RS) and vestibulospinal (VS) pathways. The axons of larger RS neurons reach the most caudal of approximately 100 spinal segments, whereas the VS pathway does not descend below the 15th segment. This study was carried out to compare functional projections of RS and VS neurons in the rostral spinal segments that the neurons innervate together. To reveal these projections, individual RS or VS neurons were stimulated, and the responses of different groups of spinal motoneurons were recorded in ventral root branches to dorsal and ventral parts of myotomes. The responses were detected using a spike-triggered averaging technique on the background of ongoing motoneuronal activity. Individual RS and VS neurons exerted uniform effects on segmental motor output within this rostral part of the spinal cord. The effects of VS neurons on different groups of motoneurons were weaker and less diverse than those of RS neurons. The results indicate that VS neurons are able to elicit a flexion of the rostral part of the body and to turn the head in different planes without affecting more caudal parts. By contrast, larger RS neurons can elicit head movement only together with movement of a considerable part of the body and thus seem to be responsible for formation of gross motor synergies."
    170 Related citations:
    5 Cited by's: 
    Full-length article:  

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


2004  48<150 
Locomotor role of the corticoreticular-reticulospinal-spinal interneuronal system.    
The corticoreticular-reticulospinal-spinal interneuronal connections appear to operate as a cohesive, yet flexible, control system for the elaboration of a wide variety of movements"  
    See:  Corticospinal Tract 

Brainstem control of activity and responsiveness in resting frog tadpoles: tonic inhibition.
    "The hatchling Xenopus laevis tadpole was used to study the brain neurons controlling responsiveness. Tadpoles have reduced motor activity and responsiveness when they hang at rest, attached by cement gland mucus. Afferent input from cement gland mechanosensory neurons has both a phasic role in stopping swimming and a tonic role in reducing responsiveness while tadpoles hang attached. Both these roles depend on GABA(A)-mediated inhibition. We provide evidence supporting the hypothesis that long-term reduced responsiveness in attached tadpoles results from tonic activity in the reticulospinal GABAergic pathway mediating the stopping response. Two groups of putative stopping pathway interneurons were recorded in the caudal and rostral hindbrain of immobilised tadpoles. Both groups showed a sustained increase in activity during simulated attachment. This attached activity was irregular and unstructured. We consider whether low-level firing in cement gland afferents (at approximately 1 Hz) during simulated attachment is sufficient to explain the low-level firing (at approximately 0.5 Hz) in reticulospinal neurons. We then ask if a small population of these neurons (approximately 20) could produce sufficient inhibition of spinal neurons to reduce the whole tadpole's responsiveness. We conclude that for most of their 1st day of life GABAergic brainstem neurons could produce inhibition continuously while the tadpole is at rest."  

2008 25<150
Initiation of locomotion in lampreys    
MLR inputs to reticulospinal cells use both glutamatergic and cholinergic transmission"  
GABA inputs tonically maintain the MLR inhibited and removal of this inhibition initiates locomotion"  

2008  21<150
Development and organization of the descending serotonergic brainstem-spinal projections in the sea lamprey.  
two serotonergic populations of the isthmic and vagal reticular regions present reticulospinal neurons from the beginning of the larval period"  
    See:   Lamprey Neurotransmitters  .  

Descending brain-spinal cord projections in a primitive vertebrate, the lamprey: cerebrospinal fluid-contacting and dopaminergic neurons.

We used Neurobiotin as a retrograde tract tracer in both larval and adult sea lampreys and observed a number of neuronal brainstem populations (mainly reticular and octaval populations and some diencephalic nuclei) that project to the spinal cord, in agreement with the results of previous tracer studies. We also observed small labeled neurons in the ventral hypothalamus, the mammillary region, and the paratubercular nucleus, nuclei that were not reported as spinal projecting. Notably, most of the labeled cells of the mammillary region and some of the ventral hypothalamus were cerebrospinal fluid-contacting (CSF-c) neurons. Combined tract tracing and immunocytochemistry showed that some of the labeled neurons of the mammillary and paratubercular nuclei were dopamine immunoreactive. In addition, some CSF-c cells were labeled in the caudal rhombencephalon and rostral spinal cord, and many were also dopamine immunoreactive. Results with other tracers (biotinylated dextran amines, horseradish peroxidase, and the carbocyanine dye DiI) also demonstrated that the molecular weight or the molecular nature of the tracer was determinant in revealing diencephalic cells with very thin axons. The results show that descending systems afferent to the spinal cord in lampreys are more varied than previously reported, and reveal a descending projection from CSF-c cells, which is unknown in vertebrates. The present results also reveal the existence of large differences between agnathans and gnathostomes in the organization of the dopaminergic cells that project to the spinal cord."  

2011  13<150 
Internal pallidum and substantia nigra control different parts of the mesopontine reticular formation in primate.  
anterograde tracing experiments revealed that the pedunculopontine nucleus and cuneiform nucleus project to large portions of the pontomedullary reticular formation"  
the nigro-cuneiform nucleus pathway could control axial posture whereas the pallido-pedunculopontine nucleus pathway could modulate locomotion"  
    See:  Mesencephalic Locomotor Region  . 

Searching PubMed for "reticular activating system spinal locomotor generator" yielded zero references. 

Reticulospinal Transmission
150622 - 1321  modified