Monosynaptic inputs to lumbar interneurons from the lateral vestibulospinal tract and the medial longitudinal fasciculus

doi:10.1016/0304-3940(78)90236-7

Neuroscience Letters

Volume 10, Issue 3, December 1978, Pages 259-264

https://doi.org/10.1016/0304-3940(78)90236-7 Get rights and content

Abstract

In anesthetized cats, the lateral vestibulospina tract (LVSTr) and the descending medial longitudinal fasciculus (MLF) were electrically stimulated in the brain stem and intracellular recordings were made from interneurons in the lumbar spinal cord. Three groups of interneurons were identified on the basis of monosynaptic EPSPs which they received (1) from only the ipsilateral LVSTr ( $3796$ ), (2) from only the ipsilateral MLF ( $3496$ ) and (3) from both tracts ( $2596$ ), indicating convergence onto this group. The somas were primarily in laminae VIII and VII, with a few in VI and X. The location of field potentials was similar to the neuronal distribution.

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Cytoarchitecture of the Spinal Cord
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This chapter describes the cellular architecture of the spinal cord. The gray matter of the spinal cord is morphologically heterogeneous. The cells of the spinal cord gray matter differ considerably in terms of size, shape and density. However, the gray matter does show some intrinsic organization, so that zones of regularity or laminae can be identified. The concept of laminae has been adopted widely for describing cytoarchitectonic boundaries in the spinal cord in many species. These laminae were first described by Rexed (1954) in the cat. Since then, the concept of laminae has been adopted widely for describing cytoarchitectonic boundaries in the spinal cord in many species, though detailed examination and description of these laminae have only been completed in the mouse and human, in addition to Rexed's original work in the cat. In general, the organization of the Rexed's laminae in these mammalian species is similar. Ten laminae are recognized and these are organized in a series of layers from dorsal to ventral, but with lamina 10 (also called area 10) found around the central canal. The chapter discusses the major cytological characteristics of each of the laminae. Many studies have shown that neurons within a lamina often show distinct dendritic architecture, chemoarchitecture and patterns of connections as well as function.
Control of locomotion in the decerebrate cat
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Many of the general concepts regarding the control of walking were described years ago by: Sherrington (1906)Integrative Actions of the Nervous System. Yale University Press: New Haven, CT; Sherrington (1910a)Remarks on the reflex mechanism of the step, Brain 33, 1–25; Sherrington (1910b)Flexor-refex of the limb, crossed extension reflex, and reflex stepping and standing (cat and dog), J. Physiol. (Lond.) 40, 28–121; Sherrington (1931)Quantitative management of contraction in lowest level coordination, Brain 54, 1–28; Graham-Brown (1912)The intrinsic factors in the act of progression in the mammal, Proc. R. Soc. Lond. 84, 308–319; Graham-Brown (1914)On the nature of the fundamental activity of the nervous centres; together with an analysis of the conditioning of rhythmic activity in progression, and a theory of the evolution of function in the nervous system, J. Physiol. 49, 18–46; Graham-Brown (1915)On the activities of the central nervous system of the unborn foetus of the cat, with a discussion of the question whether progression (walking, etc.) is a ‘learnt’ complex, J. Physiol. 49, 208–215; Graham-Brown (1922)The physiology of stepping, J. Neur. Psychopathol. 3, 112–116.
Only in recent years, however, have the mechanisms been analyzed in detail. Quite a few of these mechanisms have been described using the decerebrate cat. Locomotion is initiated in decerebrate cats by activation of the mesencephalic locomotor region (MLR) that activates the medial medullary reticular formation (MRF) which in turn projects axons to the spinal cord which descend within the ventrolateral funiculus (VLF). The MRF region regulates as well as initiates the stepping pattern and is thought to be involved in interlimb coordination. Afferent feedback from proprioceptors and exteroceptors can modify the ongoing locomotor pattern. Recently, the types of afferents responsible for signaling the stance to swing transition have been identified. A general rule states that if the limb is unloaded and the leg is extended, then swing will occur. The afferents that detect unloading of the limb are the Golgi tendon organs and stimulation of these afferents (at group I strengths) prolongs the stance phase in walking cats. The afferents that detect the extension of the leg have been found to be the lenght- and velocity-sensitive muscle afferents located in flexor muscles. Plasticity of locomotor systems is discussed briefly in this article. Decerebrate animals can adapt locomotor behaviors to respond to new environmental conditions. Oligosynaptic reflex pathways that control locomotion can be recalibrated after injury in a manner that appears to be functionally related to the recovery of the animal. Copyright © 1996 Elsevier Science Ltd.
Population synaptic potentials evoked in lumbar motoneurons following stimulation of the nucleus reticularis gigantocellularis during carbachol-induced atonia
1994, Brain Research
The effect of electrical stimulation of the medullary nucleus reticularis gigantocellularis (NRGc) on lumbar spinal cord motoneurons was studied in the decerebrate cat using sucrose-gap recordings from ventral roots. The NRGc was stimulated ipsi- and contralaterally before and during atonia elicited by the microinjection of carbachol into the pontine reticular formation. Prior to carbachol administration, the NRGc-induced response recorded from the sucrose-gap consisted of two consecutive excitatory population synaptic potentials followed by a long-lasting, smallamplitude inhibitory population synaptic potential. Following carbachol injection, the same NRGc stimulus evoked a distinct, large amplitude inhibitory population synaptic potential, whereas the excitatory population synaptic potentials decreased in amplitude. In addition, after carbachol administration, the amplitude of the monosynaptic excitatory population synaptic potential, which was evoked by stimulation of group Ia afferents in hindlimb nerves, was reduced by 18 to 43%. When evoked at the peak of the NRGc-induced inhibitory response, this potential was further decreased in amplitude. Systemic strychnine administration (0.07–0.1 mg/kg, i.v.) blocked the NRGc-induced inhibitory population synaptic potential and promoted an increase in the amplitude of the excitatory population synaptic potentials induced by stimulation of the NRGc and group Ia afferents. These data indicate that during the state of carbachol-induced atonia, the NRGc effects on ipsi- and contralateral spinal cord motoneurons are predominantly inhibitory and that glycine is likely to be involved in this inhibitory process. These results support the hypothesis that the nucleus reticularis gigantocellularis is part of the system responsible for state-dependent somatomotor inhibition that occurs during active sleep.
Interneuronal relay in spinal pathways from proprioceptors
1992, Progress in Neurobiology
Convergent effects from vestibulospinal tract and primary cutaneous afferent fibers on motoneurons to proximal lower limb flexor and extensor muscles in humans
1988, Experimental Neurology
In human subjects, the latency and magnitude of cutaneomuscular test reflexes, evoked by stimulation of the sural nerve in the contralateral and ipsilateral quadricep and hamstring muscles, were investigated during static tilts in the pitch axis. The ANOVA demonstrated a highly significant, tilt-dependent modulation of the magnitude of the test reflex for the initial phase of both ipsilateral quadriceps and ipsilateral hamstrings. These results are consistent with results from a similar study on human ankle muscles and provide further evidence that the tilt-dependence of these cutaneomuscular reflexes originates from activity in the otolith receptors.
Convergent effects from vestibulospinal tract and primary cutaneous afferent fibers on motoneurons to ankle extensor and flexor muscles in humans
1987, Experimental Neurology
The latency and magnitude of cutaneomuscular reflexes, evoked by stimulation of the sural nerve in the contralateral and ipsilateral tibialis anterior and soleus, were investigated in normal human subjects during static tilts in the pitch axis. For all subjects the test reflex consisted of oscillating sequences of excitation and inhibition, each muscle exhibiting a characteristic pattern defined by its latency and sign of the initial phase. The latency of the various components and the sign of the initial phase did not vary with angle of tilt. However, the results of an ANOVA demonstrate a highly significant tilt-dependent modulation of the amplitude of the test reflex for the initial inhibitory phase of the contralateral tibialis anterior. We propose that this tilt-dependent effect on the crossed cutaneomuscular reflex originates from activity in the otolith organ receptors.

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Monosynaptic inputs to lumbar interneurons from the lateral vestibulospinal tract and the medial longitudinal fasciculus

Abstract

Brain Res.

Brain Res.

Exp. Neurol.

Cervical branching of lumbar vestibulospinal axons

J. Physiol. (Lond.)

Neurological Anatomy in Relation to Clinical Medicine

Interaction between the vestibulospinal tract, contralateral flexor reflex afferents and Ia afferents

Brain Res.

The vestibulospinal tract. Effects on alpha-motoneurones in the lumbosacral spinal cord in the ???

Exp. Brain Res.

Convergent effects on alphamotoneurones from the vestibulospinal tract and a pathway descending the medial longitudinal fasciculus

Exp. Brain Res.

The origin of a descending pathway with monosynaptic action on flexor motoneurones

Acta physiol. scand.

The vesibulospinal tract: crossed and uncrossed effects on hindlimb motoneurones in the cat

Exp. Brain Res.