Ascending and descending projections of the lateral vestibular nucleus in the rat

The tracer neurobiotin was injected into the lateral vestibular nucleus in rat and the efferent fiber connections of the nucleus were studied. The labeled fibers reached the diencephalon rostrally and the sacral segments of the spinal cord caudally. In the diencephalon, the ventral posteromedial and the gustatory nuclei received the most numerous labeled fibers. In the mesencephalon, the inferior colliculus, the interstitial nucleus of Cajal, the nucleus of Darkschewitch, the periaqueductal gray matter and the red nucleus received large numbers of labeled fibers. In the rhombencephalon, commissural and internuclear connections originated from the lateral vestibular nucleus to all other vestibular nuclei. The medioventral (motor) part of the reticular formation was richly supplied, whereas fewer fibers were seen in the lateral (vegetative) part. In the spinal cord, the descending fibers were densely packed in the anterior funiculus and in the ventral part of the lateral funiculus. Collaterals invaded the entire gray matter from lamina IX up to lamina III; the fibers and terminals were most numerous in laminae VII and VIII. Collateral projections were rich in the cervical and lumbosacral segments, whereas they were relatively poor in the thoracic segments of the spinal cord. It was concluded that the fiber projection in the rostral direction was primarily aimed at sensory-motor centers; in the rhombencephalon and spinal cord, fibers projected onto structures subserving various motor functions.     

Projections of neurons of the hypothalamic locomotor region to some brainstem and spinal cord structures in the cat

Efferent projections of the thalamic locomotor region were investigated using the horseradish peroxidase technique of retrograde axonal transport. This enzyme was injected into different brain structures. Function was monitored during a micro-injection into the locomotor areas. It was found that direct descending projections from the hypothalamic locomotor region lead mainly to ipsilateral structures and reach the lumbar sections of the spinal cord. Neurons of the locomotor area of the hypothalamus make their major connections with thelocus coeruleus area and the medial brainstem reticular formation. Projections were observed from the hypothalamic locomotor region to the mesencephalic locomotor area and the locomotor strip.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 6, pp. 817–23, November–December, 1985.     

Efferent projections of mesencephalic locomotor neurons in the cat

Efferent neuronal projections of the mesencephalic locomotor region were investigated in cats using a horseradish peroxidase retrograde axonal transport technique. It was found that neurons located within the locomotor area form ascending and descending projections to many structures of the spinal cord and the brain but that short-axon connections running to the reticular formation of the midbrain and the medulla predominate. Small numbers of long-axon fibers may merge into the locomotor strips of the medulla and the spinal cord. The locomotor regions of the two halves of the midbrain are interlinked.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 117–125, January–February, 1986.     

An HRP study in the cat of brainstem projections to the spinal cord, with particular reference to sacral afferents

Cells of origin of the spinal projections from the brainstem of the cat have been studied by means of retrograde axonal transport of horseradish peroxidase (HRP). Following injections of HRP into various levels of the spinal cord, many labeled cells were found in several structures in the brainstem. The labeled cells occurred in the raphe nuclei, reticular formation, vestibular complex, and nuclei of the dorsolateral pontine tegmentum. In the dorsolateral pontine tegmentum, many labeled cells were found in the nuclei of locus coeruleus, subcoeruleus and K?lliker-Fuse. In the coeruleus and subcoeruleus, the greatest number of labeled cells were found, when HRP was injected into the sacral cord. No difference emerged, however, in the number of labeled cells appearing in the K?lliker-Fuse nucleus after injection of the enzyme into different levels of the spinal cord. It appears that neurons in the lateral vestibular nucleus which project to different levels of the spinal cord are located in different parts of this nucleus.     

Afferent connections of the cat caudate nucleus studied by the retrograde axonal transport method

Sources of direct and indirect afferent connections of the caudate nucleus were investigated in cats by the retrograde axonal transport of horseradish peroxidase method. Different parts of the neocortex were shown to form different types of projections to the caudate nucleus; the sources of these projections have a laminar organization. Connections of the globus pallidus with the caudate nucleus, not previously described, were found. Among the sources of the thalamo-caudate projections, besides nuclei of the intralaminar complex, an important place is occupied by the ventral anterior and mediodorsal nuclei. After injection of horseradish peroxidase into the caudate nucleus, retrograde axonal transport of the enzyme was observed in the caudal direction, as far as cells of the locus coeruleus. ON the basis of these results a general scheme of afferent projections to the caudate nucleus is drawn up, including its connections with the spinal cord mediated by the thalamic nuclei and mesencephalic reticular formation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 146–154, March–April, 1980.     

Spatial organization of vestibulospinal neurons in the guinea pig

Quantitative characteristics of spatial organization of neuron populations of vestibular nuclei, forming projections into the spinal cord, were obtained in experiments on guinea pigs by the retrograde axonal transport of horseradish peroxidase, injected unilaterally into the upper cervical and lower thoracic segments of the spinal cord, method. Neurons accumulating the enzyme were found ipsilaterally in the lateral vestibular nucleus and bilaterally in the descending and medial vestibular nuclei. The distribution of vestibulospinal neurons along the length of the spinal cord was studied. Neuron populations of the medial and descending vestibular nuclei whose projection regions coincide with those of fibers of the corticospinal and rubrospinal systems were discovered. The role of vestibulospinal systems in the structure of supra-segmental control of the neuronal apparatus of the spinal cord is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 3, pp. 353–362, May–June, 1991.     

Afferent projections to the mesencephalic locomotor region of the cat brain

Afferent projections to the functionally identified mesencephalic locomotor region were investigated in cats using the horseradish peroxidase retrograde axonal transport technique. Sources of afferent projections to this region were discovered in different structures of the fore-, mid-, and hindbrain. Numbers of horseradish peroxidase-labeled neurons were calculated in different brain structures after injecting this enzyme into the mesencephalic locomotor region. Apart from the endopeduncular nucleus, different hypothalamic structures, and the substantia nigra, labeled neurons were discovered in the central tegmental region, the central gray, raphe and vestibular nuclei, the solitary tract nucleus, and the brain stem reticular formation. Neurons accumulating horseradish peroxidase were also discovered in nuclei where ascending sensory tracts originate. This fact serves to bring out the structural inhomogeneity of the midbrain locomotor region; electrical stimulation of this area is an effect which may be attributed to excitation of neurons found within it and activation of accompanying fiber tracts.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 763–773, November–December, 1986.     

Influence of the efferent vestibular system on vestibulo-spinal reflexes in the guinea pig

The influence of the efferent vestibular system on vestibulo-spinal activity was investigated during experiments on guinea pigs decerebrated and following cerebellar extirpation at precollincular level. Efferent vestibular neurons forming compact groups ventromedially to the vestibular nuclei were excited by means of electrical stimulation. Electromyographic activity in the triceps brachii extensor muscles of the right and left forelimbs was adopted as a test reaction (crossed extensor reflex and locomotor activity produced by stimulating the mesencephalic locomotor region). Adequate stimulation of the vestibular apparatus was accomplished by static tilting and cyclic shifting of the animal around its longitudinal axis at angles of ±20°. The efferent vestibular system was found to exert a bilateral inhibitory action on vestibulo-spinal activity. Vestibular efferent stimulation produced a reduction in the intensity of vestibulo-fugal influences: it does not change the dynamics of vestibulo-spinal reflex effects, however. Mechanisms of vestibular efferent action on vestibular control of spinal motor activity are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 1, pp. 78–86, January–February, 1989.     

Localization of alcohol and aldehyde dehydrogenases in the human spinal cord and brain

Location of aldehyde dehydrogenase (AldDG) and alcohol dehydrogenase (ADG) has been studied in 38 nuclei of the human brain. Neurons with a high AldDG activity predominate in the nucleus of the descending root of the trigeminal nerve, motor nuclei of the craniocerebral nerves (trigeminal, facial, abducent, blocking, sublingual, supraspinal), motor nuclei of the anterior horns of the spinal cord, lateral vestibular nucleus, posterior nucleus of the vagus nerve, pedunculopontine nucleus, superior salivary nucleus, and in the nucleus of Westphal-Edinger-Jacobovich. Neurons with a moderate AldDG activity predominate in the superior olivary complex, nucleus of the lateral loop, parabrachial (pigmented) mesencephalic nucleus and reticular lateral nucleus. A low enzymatic activity is specific for neurons of the pons proper, inferior vestibular nucleus, trapezoid body of the inferior olivary complex, dentate nucleus of the cerebellum, reticular nucleus of the tegmen of Bekhterev's pons and posterior nucleus of Gudden's suture. A high ADG activity is revealed in piriform neurons of the cerebellar cortex. Functional importance of ADG and AldDG activity in the brain is discussed.     

Afferent connections of the cat lateral vestibular nucleus

Location within the brain of HP-labeled neurons (origins of projections to the lateral vestibular nucleus) was investigated by iontophoretic injection of this enzyme. Bilateral projections to the following midbrain structures were revealed: the field of Forel, interstitial nuclei of Cajal, oculomotor nerve nuclei, and the red nucleus — to all parts of the lateral vestibular nucleus. Bilateral projections were also shown from more caudally located structures, viz. the superior, medial and inferior (descending) vestibular nuclei, Y groups of the vestibular nuclear complex, facial nucleus and hypoglossi, nucleus prepositus nervi hypoglossi and caudal nuclei of the trigeminal tract; ipsilateral projections from crus IIa of lobulus ansiformus of the cerebellar hemisphere; contralateral projections from the bulbar lateral reticular nucleus and Deiter's nucleus. A tonic organization pattern of afferent inputs from a number of brainstem formations to the dorsal and ventral lateral vestibular nucleus is revealed and trajectories of HP-labeled fiber systems projecting to Deiter's nucleus described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 4, pp. 494–503, July–August, 1988.     

Distribution of horseradish peroxidase-labeled neurons giving rise to descending fiber systems in the basal ganglia and hypothalamus in cats

The distribution of neurons giving rise to various descending fiber systems to brain-stem structures in the basal ganglia (including amygdaloid nuclei) and hypothalamus of the cat was studied by the retrograde axonal transport of horseradish peroxidase method. Neurons in the medial part of the central nucleus and of the magnocellular part of the basal nucleus of the amygdaloid group were shown to send axons to the dorsal hippocampus, substantia nigra, lateral part of the central gray matter, and the mesencephalalic reticular formation and also to the region of the locus coeruleus and the lateral medullary reticular formation at the level of the inferior olives. The predominant source of projections to the hypothalamus and brainstem structures is the central amygdaloid nucleus, which also sends projections to the nucleus of the tractus solitarius, the dorsal motor nucleus of the vagus nerve, and the superior cervical segments of the spinal cord. Uncrossed fiber systems descending from the basal ganglia terminate at the level of the pons, whereas uncrossed and crossed fiber systems descending from the dorsal and ventromedial hypothalamus can be traced into the spinal cord. The possible role of nuclei of the amygdaloid group, the hypothalamus, and their efferent projections in the regulation of somatic and vegetative functions and also of complex behavioral reactions is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 1, pp. 14–23, January–February, 1981.     

Afferent and efferent connections of cortical transplants implanted into the damaged sensorimotor area of the cerebral cortex of mature rats

Afferent and efferent connections of the transplant, implanted in the previously damaged sensorimotor area of the mature rat cerebral cortex have been studied by means of axonal transport of horseradish peroxidase. For 5 months after transplantation neural axons of the transplant are capable to reach the caudo-putamen and thalamic structures, while connections with the spinal cord are absent. The afferent connections of the transplant are minimal and belong only to the neighbouring areas of the cortex and the caudo-putamen of the recipient brain. Presence of efferent projections to the striate and thalamic structures demonstrates specificity of the projections formed; this can be a morphological base for restoration of the functions lost after the damage of the sensorimotor area of the cortex in mature animals.     

Autoradiographic distribution of 125I calcitonin gene-related peptide binding sites in the rat central nervous system

Using autoradiographic method and 125I-Tyro rat CGRP as a ligand, receptor binding sites were demonstrated in the rat central nervous system. Saturation studies and Scatchard analysis of CGRP-binding to slide mounted tissue sections containing primarily cerebellum showed a single class of receptors with a dissociation constant of 0.96 nM and a Bmax of 76.4 fmol/mg protein. 125I-Tyro rat CGRP binding sites were demonstrated throughout the rat central nervous system. Dense binding was observed in the telencephalon (medial prefrontal, insular and outer layers of the temporal cortex, nucleus accumbens, fundus striatum, central and inferior lateral amygdaloid nuclei, most caudal caudate putamen, organum vasculosum laminae terminalis, subfornical organ), the diencephalon (anterior hypothalamic, suprachiasmatic, arcuate, paraventricular, dorsomedial, periventricular, reuniens, rhomboid, lateral thalamic pretectalis and habenula nuclei, zona incerta), in the mesencephalon (superficial layers of the superior colliculus, central nucleus of the geniculate body, inferior colliculus, nucleus of the fifth nerve, locus coeruleus, nucleus of the mesencephalic tract, the dorsal tegmental nucleus, superior olive), in the molecular layer of the cerebellum, in the medulla oblongata (inferior olive, nucleus tractus solitarii, nucleus commissuralis, nuclei of the tenth and twelfth nerves, the prepositus hypoglossal and the gracilis nuclei, dorsomedial part of the spinal trigeminal tract), in the dorsal gray matter of the spinal cord (laminae I-VI) and the confines of the central canal. Moderate receptor densities were found in the septal area, the "head" of the anterior caudate nucleus, medial amygdaloid and bed nucleus of the stria terminalis, the pyramidal layers of the hippocampus and dentate gyri, medial preoptic area, ventromedial nucleus, lateral hypothalamic and ventrolateral thalamic area, central gray, reticular part of the substantia nigra, parvocellular reticular nucleus. Purkinje cell layer of the cerebellum, nucleus of the spinal trigeminal tract and gracile fasciculus of the spinal cord. The discrete distribution of CGRP-like binding sites in a variety of sensory systems of the brain and spinal cord as well as in thalamic and hypothalamic areas suggests a widespread involvement of CGRP in a variety of brain functions.     

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 810–816, November–December, 1987.     

The organization of the corticonuclear and olivocerebellar climbing fiber projections to the rat cerebellar vermis: The congruence of projection zones and the zebrin pattern

The zonal organization of the corticonuclear and the olivocerebellar climbing fiber projections to the vermis of the cerebellum of the rat was compared to the pattern of zebrin-positive and zebrin-negative bands in material double-stained for zebrin II and for different anterograde tracers injected in subnuclei of the inferior olive, or retrograde tracers injected in the cerebellar and vestibular target nuclei of the Purkinje cells of the vermis. Projection zones A₁, A_X, X, B, C_X in the vermis and A₂ (accessory A zone) and C₂ in the hemisphere were defined by their efferent corticonuclear and their afferent climbing fiber connections, and were found to share the same topographical framework with the zebrin pattern.     

Connections of brainstem respiratory nuclei studied by the retrograde horseradish peroxidase axon transport method

Intrabulbar connections of respiratory nuclei and the medullary reticular formation and also descending pathways from these structures in the spinal cord were studied by the retrograde horseradish peroxidase axonal transport method in cats. Neurons of the nucleus ambiguus and nucleus retroambigualis (ventral respiratory group) and of the ventrolateral part of the nucleus of the tractus solitarius (dorsal respiratory group) were shown to form direct two-way connections with each other and with the medial region of the medulla. Neurons of the pneumotaxic center send uncrossed axons to the nucleus ambiguus and to the medial medullary reticular formation. Neurons of the contralateral homonymous nucleus and neurons of the nucleus of the tractus solitarius are sources of projections of the locus coeruleus. A well developed system of direct connections was found between neurons of respiratory nuclei of the two halves of the brain. The possible role of these nuclear formations in genesis of the respiratory rhythm and regulation of the respiratory and other motor functions of the reticular formation is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 149–157, March–April, 1982.     

Neuronal mechanisms of interaction between the red nucleus and other brain stem structures

Axon collaterals of rubrospinal neurons running to many brain stem structures were identified in acute experiments on cats by a technique of intracellular recording of antidromic action potentials in conjunction with collision testing. A systemic principle of organization of rubrospinal influences and also a tendency toward synchronous arrival of rubrospinal impulses at various brain stem centers were demonstrated. Most of these centers are relay nuclei, sending direct afferent projections to regions of the cerebellum which, in turn, control activity of the red nucleus. Besides such a loop, effecting dynamic cerebellar control over motor function, transmission of somatosensory information from nuclei of the dorsal columns of the spinal cord directly to the red nucleus was demonstrated. Special features of mono- and polysynaptic EPSPs evoked by stimulation of nuclei of the dorsal columns indicate that such PSPs arise in different regions of the soma-dendritic membrane of red nucleus neurons. The mechanisms of integration of descending motor volleys by the red nucleus are discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 16, No. 5, pp. 665–678, September–October, 1984.     

Somatostatin-immunoreactive fiber projections into the brain stem and the spinal cord of the rat

Summary By use of the PAP-immunohistochemical staining technique with serial sections, somatostatin-immunoreactive fiber projections into the brain stem and the spinal cord are described. These projections originate in the periventricular somatostatin-immunoreactive perikarya of the hypothalamus and form three main pathways: (1) along the stria medullaris thalami and the fasciculus retroflexus into the interpeduncular nucleus; (2) along the medial forebrain bundle into the mammillary body; and (3) via the periventricular gray and the bundle of Schütz into the midbrain tegmentum. Densely arranged immunoreactive fibers and/or basket-like fiber terminals are observed within the following afferent systems: somatic afferent systems (nucleus spinalis nervi trigemini, substantia gelatinosa dorsalis of the entire spinal cord), and visceral afferent systems (nucleus solitarius, regio intermediolateralis and substantia gelatinosa of the sacral spinal cord). These projections form terminals around the perikarya of the second afferent neuron. Perikarya of the third afferent neuron are influenced by somatostatin-immunoreactive projections into the auditory system (nucleus dorsalis lemnisci lateralis, nucleus corporis trapezoidei). Furthermore, a somatostatin-immunoreactive fiber projection is found in the ventral part of the medial accessory olivary nucleus, in nuclei of the limbic system (nucleus habenularis medialis, nuclei supramamillaris and mamillaris lateralis) and in the formatio reticularis (nucleus Darkschewitsch, nuclei tegmenti lateralis and centralis, nucleus parabrachialis lateralis, as well as individual perikarya of the reticular formation). Targets of these projections are interneurons within interlocking neuronal chains.Supported by the Deutsche Forschungsgemeinschaft (Grant Nr. Kr 569/3) and Stiftung Volkswagenwerk     

Vestibulospinal system organization in vertebrates

The data on the vestibular nuclear complex and vestibulospinal systems in vertebrates are reviewed. Literature data on the topography, structure, and fiber connections of vestibular cell groups forming descending projections and the effects on the spinal cord and skeletal muscles are summarized. Current conceptions of the structural and functional specificity of different vestibulospinal systems are discussed.O. O. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 2, pp. 215–238, March–April, 1992.     

Spinal projections of brainstem respiratory related neurons in the cat as revealed by retrograde fluorescent markers

By means of retrograde axonal transport of fluorescent tracers, connections between brainstem respiratory related regions and the spinal cord has been studied in the cat. Neurons at the pneumotaxic center project bilaterally (90% ipsi-, 10% contra-) to cervical and lumbar spinal cord and ipsilaterally to thoracic levels. The ventrolateral nucleus of the tractus solitarius project mainly contralaterally (85%) to cervical levels and only contralaterally to thoracic levels; no efferent projections were found to lumbar levels. The ventral respiratory group showed a great number of neurons projecting to the spinal cord especially from the nucleus retroambiguus. Both nuclei, ambiguus and retroambiguus, project mainly contralaterally (70%) to the spinal cord. The B?tzinger complex showed rather scarce bilateral projections to cervical and only ipsilateral projections to lower cervical, thoracic and lumber levels.