Development and characterization of pathways descending to the spinal cord in the embryonic chick

1995 ◽  
Vol 73 (3) ◽  
pp. 1223-1233 ◽  
Author(s):  
G. N. Sholomenko ◽  
M. J. O'Donovan
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Motor Activity ◽  
Brain Stem ◽  
Reticular Formation ◽  
Cervical Spinal Cord ◽  
Embryonic Chick ◽  
Medullary Reticular Formation ◽  
Lumbosacral Spinal Cord ◽  
The Brain

1. We used an isolated preparation of the embryonic chick brain stem and spinal cord to examine the origin, trajectory, and effects of descending supraspinal pathways on lumbosacral motor activity. The in vitro preparation remained viable for < or 24 h and was sufficiently stable for electrophysiological, pharmacological, and neuroanatomic examination. In this preparation, as in the isolated spinal cord, spontaneous episodes of both forelimb and hindlimb motor activity occur in the absence of phasic afferent input. Motor activity can also be evoked by brain stem electrical stimulation or modulated by the introduction of neurochemicals to the independently perfused brain stem. 2. At embryonic day (E)6, lumbosacral motor activity could be evoked by brain stem electrical stimulation. At E5, neither brain stem nor spinal cord stimulation evoked activity in the lumbosacral spinal cord, although motoneurons did express spontaneous activity. 3. Lesion and electrophysiological studies indicated that axons traveling in the ventral cord mediated the activation of lumbosacral networks by brain stem stimulation. 4. Partition of the preparation into three separately perfused baths, using a zero-Ca2+ middle bath that encompassed the cervical spinal cord, demonstrated that the brain stem activation of spinal networks could be mediated by long-axoned pathways connecting the brain stem and lumbosacral spinal cord. 5. Using retrograde tracing from the spinal cord combined with brain stem stimulation, we found that the brain stem regions from which spinal activity could be evoked lie in the embryonic reticular formation close to neurons that send long descending axons to the lumbosacral spinal cord. The cells giving rise to these descending pathways are found in the ventral pontine and medullary reticular formation, a region that is the source of reticulospinal neurons important for motor activity in adult vertebrates. 6. Electrical recordings from this region revealed that the activity of some brain stem neurons was synchronized with the electrical activity of lumbosacral motoneurons during evoked or spontaneous episodes of rhythmic motor activity. 7. Both brain stem and spinal cord activity could be modulated by selective application of the glutamate agonist N-methyl-D-aspartate to the brain stem, supporting the existence of functionally active descending projections from the brain stem to the spinal cord. It is not yet clear what role the brain stem activity carried by these pathways has in the genesis and development of spinal cord motor activity.

Connections of midbrain periaqueductal gray in the monkey. II. Descending efferent projections

1983 ◽  
Vol 49 (3) ◽  
pp. 582-594 ◽  
Author(s):  
P. W. Mantyh
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Reticular Formation ◽  
Cervical Spinal Cord ◽  
Great Majority ◽  
Periaqueductal Gray ◽  
Locus Ceruleus ◽  
Contralateral Projection ◽  
Efferent Projections ◽  
The Brain

1. We have defined the descending efferent projections of the midbrain periaqueductal gray (PAG) by injecting small amounts of [3H]leucine into the various regions of the squirrel monkey PAG. 2. Despite the fact that different regions of the PAG were injected in separate animals, the majority of the brain stem areas labeled remained constant. 3. The PAG exhibited a dense projection to the superior colliculus, the nucleus cuneiformis, and the locus ceruleus. Parts of the reticular formation (nucleus reticularis: pontis oralis, pontis caudalis, gigantocellularis, magnocellularis, and ventralis) received a projection from the PAG, as did the nucleus parabrachial pars lateralis, ambiguous, the nucleus raphe magnus, and raphe pallidus. 4. In contrast to the brain stem, the deep laminae of the nucleus caudalis and the deep laminae of the cervical spinal cord were labeled only after injections of the lateral aspect of the PAG. 5. The main route for the PAG leads to brain stem projections is through the lateral edge of the paramedian reticular formation. The great majority of the anterograde labeling was ipsilateral to the injection although a small contralateral projection was present. 6. These results indicate that the PAG projects to the brain stem and spinal cord in the monkey. Many of the brain stem areas that the PAG projects to are known to project to the spinal cord. These secondary spinal projections coupled with the direct PAG leads to spinal projection provide a wide variety of routes through which the PAG may influence spinal cord activity.

scholarly journals Atonia-Related Regions in the Rodent Pons and Medulla

2000 ◽  
Vol 84 (4) ◽  
pp. 1942-1948 ◽  
Author(s):  
T. Hajnik ◽  
Y. Y. Lai ◽  
J. M. Siegel
Keyword(s):  
Electrical Stimulation ◽  
Brain Stem ◽  
Reticular Formation ◽  
Muscle Tone ◽  
Neck Muscle ◽  
Medullary Reticular Formation ◽  
Anatomical Distribution ◽  
Hindlimb Muscles ◽  
The Brain ◽  
Stimulation Of

Electrical stimulation of circumscribed areas of the pontine and medullary reticular formation inhibits muscle tone in cats. In this report, we present an analysis of the anatomical distribution of atonia-inducing stimulation sites in the brain stem of the rat. Muscle atonia could be elicited by electrical stimulation of the nuclei reticularis pontis oralis and caudalis in the pons as well as the nuclei gigantocellularis, gigantocellularis alpha, gigantocellularis ventralis, and paragigantocellularis dorsalis in the medulla of decerebrate rats. This inhibitory effect on muscle tone was a function of the intensity and frequency of the electrical stimulation. Average latencies of muscle-tone suppressions elicited by electrical stimulation of the pontine reticular formation were 11.02 ± 2.54 and 20.49 ± 3.39 (SD) ms in the neck and in the hindlimb muscles, respectively. Following medullary stimulation, these latencies were 11.29 ± 2.44 ms in the neck and 18.87 ± 2.64 ms in the hindlimb muscles. Microinjection of N-methyl-d-aspartate (NMDA, 7 mM/0.1 μl) agonists into the pontine and medullary inhibitory sites produced muscle-tone facilitation, whereas quisqualate (10 mM/0.1 μl) injection induced an inhibition of muscle tone. NMDA-induced muscle tone change had a latency of 31.8 ± 35.3 s from the pons and 10.5 ± 0.7 s from the medulla and a duration of 146.7 ± 95.2 s from the pons and 55.5 ± 40.4 s from the medulla. The latency of quisqualate (QU)-induced reduction of neck muscle tone was 30.1 ± 37.9 s after pontine and 39.5 ± 21.8 s after medullary injection. The duration of muscle-tone suppression induced by QU injection into the pons and medulla was 111.5 ± 119.2 and 169.2 ± 145.3 s. Smaller rats (8 wk old) had a higher percentage of sites producing muscle-tone inhibition than larger rats (16 wk old), indicating an age-related change in the function of brain stem inhibitory systems. The anatomical distribution of atonia-related sites in the rat has both similarities and differences with the distribution found in the cat, which can be explained by the distinct anatomical organization of the brain stem in these two species.

Cervical spinal cord in experimental hydrocephalus

1972 ◽  
Vol 37 (5) ◽  
pp. 538-542 ◽  
Author(s):  
George J. Dohrmann
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Cervical Spinal Cord ◽  
Central Canal ◽  
Content Type ◽  
Experimental Hydrocephalus ◽  
Physiological Pressure ◽  
The Brain ◽  
Shunting Procedure ◽  
Fine Print

✓ Adult dogs were rendered hydrocephalic by the injection of kaolin into the cisterna magna. One group of dogs was sacrificed 1 month after kaolin administration, and ventriculojugular shunts were performed on the other group. Hydrocephalic dogs with shunts were sacrificed 1 day or 1 week after the shunting procedure. All dogs were perfused with formalin at physiological pressure, and the brain stem and cervical spinal cord were examined by light microscopy. Subarachnoid granulomata encompassed the superior cervical spinal cord and dependent surface of the brain stem. Rarefaction of the posterior white columns and clefts or cavities involving the gray matter posterior to the central canal and/or posterior white columns were present in the spinal cords of both hydrocephalic and shunted hydrocephalic dogs. Predominantly in the dogs with shunts, hemorrhages were noted in the spinal cord in association with the clefts or cavities. A mechanism of ischemia followed by reflow of blood is postulated to explain the hemorrhages in the spinal cords of hydrocephalic dogs with shunts.

scholarly journals Morphologic and Immunoperoxidase Study of Neurologic Lesions in Naturally Acquired Rabies of Raccoons

1992 ◽  
Vol 4 (4) ◽  
pp. 369-373 ◽  
Author(s):  
A. N. Hamir ◽  
G. Moser ◽  
C. E. Rupprecht
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Ganglion Cells ◽  
Cervical Spinal Cord ◽  
Fluorescent Antibody ◽  
Antibody Test ◽  
Immunoperoxidase Method ◽  
Spinal Cord Regions ◽  
Trigeminal Nerves ◽  
The Brain

Histopathologic (hematoxylin and eosin [HE]) and immunoperoxidase (streptavidin-biotin complex) methods were used for examination of formalin-fixed tissues of rabid raccoons from an enzootic area of Pennsylvania. Extensive morphologic lesions of rabies encephalitis were present in the cerebrum and the brain stem regions. Negri bodies were detected by both methods and were present in the brain (cerebral cortex, hippocampus, brain stem, cerebellum, and cervical spinal cord) and in the ganglia of the trigeminal nerves. The viral inclusions were also seen in ganglion cells in the tongue, parotid salivary glands, pancreas, intestines, and adrenal glands. These sites were not associated with any inflammatory cellular infiltrate. The immunoperoxidase method was superior to HE for the detection of Negri bodies. Because lesions of rabies encephalitis were consistently observed in the cerebrum, brain stem, and cervical spinal cord regions, these areas of the brain should be included when raccoons are examined by the fluorescent antibody test for rabies.

Functional organization within the medullary reticular formation of intact unanesthetized cat. I. Movements evoked by microstimulation

1990 ◽  
Vol 64 (3) ◽  
pp. 767-781 ◽  
Author(s):  
T. Drew ◽  
S. Rossignol
Keyword(s):  
Brain Stem ◽  
Reticular Formation ◽  
Functional Organization ◽  
The Body ◽  
Large Area ◽  
Medullary Reticular Formation ◽  
Discrete Movements ◽  
The Brain ◽  
Flexion And Extension ◽  
Made In

1. The present article described the various patterns of movement evoked in the limbs and neck by microstimulation (33-ms trains, 330 Hz, 0.2-ms pulses at less than or equal to 35 microA) of the medullary reticular formation (MRF) of seven chronically implanted, unanesthetized, intact cats. Altogether 878 loci were stimulated in 83 penetrations. However, as stimulation in the more lateral regions of the MRF was less effective, the results are based on stimulation in 592 loci made in 56 penetrations at distances of between 0.5 and 2.5 mm lateral to the midline. 2. Of these 592 loci, movement of one or more parts of the body was evoked from a total of 539 (91%) sites. Most of these movements were compound in nature, involving movement of one or more limbs as well as the head. Discrete movements were observed only with respect to the head; limb movements were always accompanied by head movement. In addition, hindlimb movements were always accompanied by forelimb movements, although the inverse was generally not true. 3. The most common effects of the stimulation were as follows: a turning of the head to the ipsilateral side (79% of stimulated sites); flexion of the ipsilateral elbow (41%); and extension of the contralateral elbow (45%). Effects in the hindlimbs were more variable and less frequent, with the majority of the effective loci causing flexion of the ipsilateral knee (9%) together with extension of the contralateral knee (8%). In total, including both flexion and extension, 18% of the stimulated sites caused movement of the ipsilateral hindlimb and 11% of the contralateral hindlimb. 4. Although movements of the head were obtained from the whole extent of the brain stem, movements of the forelimbs showed a dorsoventral organization with flexion of the ipsilateral elbow being evoked from the more dorsal regions of the brain stem, whereas contralateral elbow extension was evoked more frequently from the ventral regions. There was a large area of overlap from which movements of both limbs could be obtained simultaneously. Movements of the hindlimbs were more frequently evoked from central and ventral areas of the brain stem and from the most rostral aspect of the explored region. 5. In examining the combinations of movements evoked by the MRF stimulation, it was found that the most commonly evoked pattern was movement of the head to the stimulated side together with flexion of the ipsilateral forelimb and extension of the contralateral forelimb (26.5% of sites).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Crossed activation of thoracic trunk motoneurons by medullary reticulospinal neurons

2019 ◽  
Vol 122 (6) ◽  
pp. 2601-2613
Author(s):  
Brandon K. LaPallo ◽  
Andrea Giorgi ◽  
Marie-Claude Perreault
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Brain Stem ◽  
Neural Circuits ◽  
Single Cells ◽  
The Other ◽  
Medullary Reticular Formation ◽  
Functional Connections ◽  
Cord Injury ◽  
The Brain

Activation of contralateral muscles by supraspinal neurons, or crossed activation, is critical for bilateral coordination. Studies in mammals have focused on the neural circuits that mediate cross activation of limb muscles, but the neural circuits involved in crossed activation of trunk muscles are still poorly understood. In this study, we characterized functional connections between reticulospinal (RS) neurons in the medial and lateral regions of the medullary reticular formation (medMRF and latMRF) and contralateral trunk motoneurons (MNs) in the thoracic cord (T7 and T10 segments). To do this, we combined electrical microstimulation of the medMRF and latMRF and calcium imaging from single cells in an ex vivo brain stem-spinal cord preparation of neonatal mice. Our findings substantiate two spatially distinct RS pathways to contralateral trunk MNs. Both pathways originate in the latMRF and are midline crossing, one at the level of the spinal cord via excitatory descending commissural interneurons (reticulo-commissural pathway) and the other at the level of the brain stem (crossed RS pathway). Activation of these RS pathways may enable different patterns of bilateral trunk coordination. Possible implications for recovery of trunk function after stroke or spinal cord injury are discussed. NEW & NOTEWORTHY We identify two spatially distinct reticulospinal pathways for crossed activation of trunk motoneurons. Both pathways cross the midline, one at the level of the brain stem and the other at the level of the spinal cord via excitatory commissural interneurons. Jointly, these pathways provide new opportunities for repair interventions aimed at recovering trunk functions after stroke or spinal cord injury.

Differential Effects of the Reticulospinal System on Locomotion in Lamprey

1998 ◽  
Vol 80 (1) ◽  
pp. 103-112 ◽  
Author(s):  
T. Wannier ◽  
T. G. Deliagina ◽  
G. N. Orlovsky ◽  
S. Grillner
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Reticular Formation ◽  
Reticular Nucleus ◽  
Caudal Part ◽  
Ventral Roots ◽  
Reticular Nuclei ◽  
The Brain ◽  
Rostral Part ◽  
Different Parts

Wannier, T., T. G. Deliagina, G. N. Orlovsky, and S. Grillner. Differential effects of the reticulospinal system on locomotion in lamprey. J. Neurophysiol. 80: 103–112, 1998. Specific effects of stimulating different parts of the reticulospinal (RS) system on the spinal locomotor pattern are described in lamprey. In the in vitro brain stem and spinal cord preparation, microstimulation in different areas of the reticular formation was performed by ejecting a small amount of d-glutamate from a micropipette. These areas were distributed over the four reticular nuclei of the brain stem: the mesencephalic reticular nucleus (MRN) and the anterior, middle and posterior rhombencephalic reticular nuclei (ARRN, MRRN, and PRRN, respectively). To prevent synaptic spread of excitation within the brain stem, the synaptic transmission was blocked by using a low Ca2+, high Mn2+ physiological saline in the brain stem pool. “Fictive” locomotion was evoked by applying N-methyl-d-aspartate (NMDA) to the spinal cord. Rhythmical discharges of motoneurons were recorded bilaterally in the midbody area, from the ventral roots that had been subdivided in dorsal and ventral branches, supplying the dorsal and ventral part of the myotome, respectively. Two major effects of brain stem stimulation were elicited: a change in the frequency of the locomotory rhythm and an induction of asymmetry (left/right, dorsal/ventral) in the segmental motor output. Approximately 50% of the stimulated sites evoked a change in locomotor frequency. In the PRRN almost all effective sites evoked an increase in frequency (10–50%). In the other nuclei, increase and decrease (10–30%) were observed equally frequently. Most of the stimulated sites (50–80%) in any reticular nucleus evoked asymmetry in the segmental motor output. Distortion of the segmental output symmetry was classified into eight categories by comparing the intensity of locomotor bursts in the dorsal and ventral branches of the two ventral roots, ipsilateral and contralateral to the stimulated side. These categories differed in the direction of the body flexion, which would be evoked during normal swimming: ipsilateral (I), contralateral (C), dorsal (D), ventral (V), ipsilateral and dorsal (ID), ipsilateral and ventral (IV), contralateral and dorsal (CD), and contralateral and ventral (CV). The different categories were not equally represented in each nucleus and across the nuclei. The most pronounced categories for each nucleus were as follow. In MRN: I (33%); ARRN: C (44%); MRRN: rostral part, I (36%) and caudal part, CV (42%); and PRRN: rostral part, I (40%) and caudal part, IV (35%). Other categories were also present but less common in each nucleus. To examine if the effects of brain stem stimulation were uniform along the spinal cord, recordings were performed from distal parts of the cord. Stimulation of a given point in the brain stem produced similar pattern of effects in 59% of cases and different patterns in 41% of cases. The main conclusion of the present study is that 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. The specificity of RS influences may represent a basis for modifications of the segmental locomotor output necessary for the control of equilibrium and steering during locomotion.

Intraoperative SEP monitoring in neurosurgery around the brain stem and cervical spinal cord: differential recording of subcortical components

1994 ◽  
Vol 81 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Wolfgang Wagner ◽  
Lydia Peghini-Halbig ◽  
Johannes C. Mäurer ◽  
Axel Perneczky
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Cervical Spinal Cord ◽  
False Negative ◽  
False Negative Rate ◽  
Content Type ◽  
Negative Rate ◽  
Neurosurgical Patients ◽  
The Brain

✓ The results of intraoperative monitoring of median nerve somatosensory evoked potentials (SEP's) were evaluated in 75 neurosurgical patients in order to assess the role of differential derivation of brain stem (P14) and spinal cord (N13) wave activity. These components were compared with the conventionally recorded neck potential (“N13”) that reflects overlap of P14 and N13. The spinal cord N13 wave was recorded from the posterior to anterior lower aspect of the neck and the brain stem P14 wave from the midfrontal scalp to the nasopharynx; both derivations enabled isolated low-artifact recording of these components. In 18.7% of patients, moderate to major latency and/or amplitude shifts of N13 or P14 were found that were masked in conventional neck-scalp recordings of “N13”. There was a 6.7% false-negative rate in this series. Using a neck-scalp derivation alone, a 14.7% false-negative rate would have resulted and an isolated worsening of the P14 component (with stable neck potential) in six cases would have been overlooked. It is concluded that the proposed SEP recording technique allows independent assessment of spinal cord and brain stem activity. It is, therefore, superior to the conventional neck-scalp derivation technique, in which important information may be concealed or even lost due to the overlap of the brain stem P14 and spinal cord N13 potentials.

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