Synaptic links of propriospinal neurons of the lumbar section of the cat spinal cord

The distribution of propriospinal fiber terminals of the lateral funiculus in the lumbar segments of the cat spinal cord was examined by light and electron microscopy. For the selective demonstration of these terminals, preliminary hemisectioning of the brain at the boundary of the thoracic and lumbar segment, eliminating all the long descending pathways, and subsequent hemisectioning or sectioning of the lateral funiculus at the level of the third lumbar segment was carried out. It was established by staining the degenerating endings (by the Fink—Heimer method) that the terminals of the descending and ascending propriospinal fibers, which form part of the lateral and ventral funiculi, are located mainly in the lateral and medial parts of lamina VII and the dorsal section of lamina VIII, according to Rexed, as well as in the regions adjacent to the dorsolateral and ventromedial motor nuclei. A large number of these terminals is found in the corresponding regions of the gray matter on the contralateral side of the brain. Since, in the case of selective injury of the lateral funiculus the number of degenerating terminals in lamina VIII is noticeably decreased, it can be assumed that the propriospinal neuron terminals of the ventral funiculus are concentrated mainly in lamina VIII. The axons of the propriospinal neurons extend over several segments both in the ascending and in the descending directions. It was shown in an electron microscopic study of the regions in which most of the propriospinal terminals are located that these terminals are of an axo-dendritic nature and terminate in the dendrites of both inter- and motor neurons. Their degeneration can be of the "light" or "dark" type.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 401–407, July–August, 1971.     

Experimental morphological study of primary afferent terminals at the base of the dorsal horn of the cat spinal cord

The distribution and ultrastructure of primary afferent terminals in the gray matter of the cervical and lumbar regions of the cat spinal cord were studied by the experimental degeneration method of Fink and Heimer. Most preterminals of primary afferents were shown to be concentrated in the region of the intermediate nucleus of Cajal (central part of Rexed's laminae VI–VII), in the substantial gelatinosa (laminae II–III), and in the nucleus proprius of the dorsal horn (central and medial parts of lamina IV). Fewer are found in the region of the motor nuclei. The number of degenerating axon terminals in the lateral parts of laminae IV and V differed: 31.5 and 0.4% respectively of all axon terminals. Many terminals of primary afferents in lamina IV contribute to the formation of glomerular structures in which they exist as terminals of S-type forming axo-axonal connections with other terminals. These results are in agreement with electrophysiological data to show that interneurons in different parts of the base of the dorsal horn differ significantly in the relative numbers of synaptic inputs formed by peripheral afferents and descending systems.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 406–414, July–August, 1973.     

Neuronal organization of the medial part of the ventral horn of the cat spinal cord

An electron-microscopic study was made of the normal structure of the medial part of the ventral horn (Rexed's laminae VII and VIII) in the cervical portion of the cat's spinal cord, the region where fibers of reticulospinal and vestibulospinal tracts terminate. Neurons of this region can be divided on the basis of the density of their cytoplasmic matrix into "light" and "dark," the dark being much more numerous in this area (26% of the total number counted) than in other parts of the gray matter of the spinal cord. The mean diameter of the soma of the dark cells is smaller than that of the light cells, and it usually is 15–20 µ. Dendrites of the neurons can also be subdivided into "light" and "dark" respectively. The surface of the former is comparatively simple in shape with a small number of appendages and spine-like structures. On the surface of the dark dendrites there are many projections and irregularly shaped lacunae. The glial cells and their processes often completely cover the surface of the soma of the small neurons, and synaptic endings are found on it only where the dendrites leave the soma. Analysis of 1000 randomly chosen synaptic endings showed that 76.1% of them form axo-dendritic synapses, 14.2% axo-somatic, and 9.7% axo-axonal synapses. Of the total number of endings 50.9% contain spherical and 40.9% flattened synaptic vesicles. Some synaptic endings contain special structures under the postsynaptic membrane and have osmiophilic synaptic vesicles. The possible functional role of the pattern of neuronal organization revealed in this region is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 176–183, March–April, 1972.     

Structural characteristics of connections between medial descending systems and spinal neurons

Structural and ultrastructural changes in the medial part of the ventral horn were studied in segments of the cat spinal cord following destruction of the ventral column at the level C₁–C₂. Analysis of results obtained by the Fink — Heimer method showed that degenerating preterminals occur mainly in Rexed's lamina VIII and also in ventromedial zones of lamina VII. Preterminals of descending pathways of the ventral column are also found in the intermediate nucleus of Cajal (central part of lamina VI) and in the ventromedial motor nucleus. Fewer of these preterminals are present in the thoracic and, in particular, in the lumbar segments. Staining by the Holländer — Vaaland method revealed degenerating myelinated axons of small diameter (3–5 µ), evidently collaterals of descending fibers entering the gray matter, in lamina VIII. Degenerative changes in myelinated axons may be manifested either as marked condensation and shrinking or as the appearance of numerous neurofilaments, polymembraneous structures, and cytolysomes. Degeneration also affects axon terminals (axo-dendritic, axo-somatic, and axo-axonal) with spherical or flattened synaptic vesicles. Counting the relative numbers of intact terminals of the various types and their comparison with the corresponding figures for normal animals shows that most connections of descending fibers with spinal neurons are axo-dendritic in character. No degenerating terminals were found on the soma of the "dark" neurons or their processes.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 6, pp. 579–586, November–December, 1972.     

Connections between the parietal cortex with the lateral suprasylvian gyrus (Clare-Bishop area) and auditory cortex in cats

Projections between areas 5 and 7 and the lateral suprasylvian gyrus (Clare-Bishop area) were investigated using anterograde degeneration techniques. This showed a topographic organization of projections from areas 5 and 7 to the lateral suprasylvian gyrus. Area 5 association fibers terminate mainly in the anterior portion of the lateral suprasylvian gyrus; this corresponds to the intermediate zone and anterior section of the posterior suprasylvian region. Area 7 efferents are located more caudally, terminating in the posterior section of the intermediate zone and in the posterior region, excluding the outer posterior limits. Fields 5 and 7 give rise to single efferent fibers terminating in the auditory cortex. Fibers from area 5 terminate in the medial ectosylvian and medial, sylvian gyri, i.e., in zones Al and AII or areas 22 and 50. A projection from area 7 terminates at the superior border of the medial ectosylvian gyrus, corresponding to the upper limit of zone A1 or areas 22 and 50.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 739–745, November–December, 1990.     

Synaptic connections of fibers of the rubrospinal tract in the cat spinal cord

The ultrastructure of the lateral part of laminae VI and VII of the spinal gray matter (the location of most of the terminal branches of the rubrospinal tract) was investigated in cats under normal conditions and at various times after destruction of the red nucleus. The neuron population of this region is formed by cells fairly homogeneous in size (25–40µ). The structure of the dendritic profiles is simple and they carry only infrequent and small membranous appendages. Most synapses are axo-dendritic. The axon terminals are divided into three groups depending on the size and shape of the synaptic vesicles and the presence of post-synaptic specialization. A few glomerular axon terminals contacting with various structures are found. Small axon terminals located chiefly on dendrites and their appendages show degenerative changes 1–8 days after destruction of the red nucleus. As a rule the degenerating terminals contain round synaptic vesicles. The glomerular terminals do not degenerate.A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 6, No. 6, pp. 610–618, November–December, 1974.     

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.     

Immunohistochemical study on the distribution of serotonin fibers in the spinal cord of the dog

Summary Distribution of serotonin fibers in the spinal cord of the dog was investigated by means of a modified PAP method; a rabbit anti-serotonin serum prepared in the laboratory of the authors was used in this study. Serotonin fibers were revealed as PAP-positive dark-brown elements displaying dot-like varicosities (0.5–2.0 m in diameter). In the spinal cord of the dog, the distribution of serotonin fibers is extensive. These fibers occur more densely in more caudal segments and are most prominent at the sacrococcygeal level. From the level of the cervical spinal cord to the upper lumbar region, the descending serotonin fibers are located immediately under the pia mater in the ventrolateral portion of the lateral funiculus. In more caudal segments, serotonin fibers are dispersed throughout the ventral and lateral funiculi. These longitudinal en passage-fibers send numerous transverse collaterals to the gray matter. Serotonin fibers are distributed abundantly in the laminae I and III of the posterior column, while only a few fibers are found in the lamina II (substantia gelatinosa). In the intermediate zone, two descending serotonin pathways, i.e., lateral and medial longitudinal bundles, are observed to coincide topographically with the nucleus intermediolateralis at C8(T1)-L3(L4) and the nucleus intermediomedialis at C1-Co respectively. The former is particularly prominent and communicates with the contralateral bundle via commissural bundles at intervals of 300–500 m. The large motoneurons in the anterior column, especially those in the nucleus myorabdoticus lateralis within the cervical and lumbar enlargements, are closely surrounded by fine networks of serotonin fibers and terminals.Supported by a grant (No. 56440022) from the Ministry of Education, Science and Culture, Japan     

Neuronal organization of the periaqueductal gray matter in the cat midbrain

It is shown by the use of Golgi's method in Antonova's modification that the neuronal structure of the periaqueductal gray matter (PGM) in the frontal plane is characterized by the presence of small and medium-sized cells of "reticular type," which can be subdivided into three types: fusiform, triangular, and multipolar. On the basis of the visual distribution of these types of neurons and also of statistical analysis of 800 identified neurons, two regions can be distinguished: medial, directly surrounding the aqueduct of Sylvius, containing small neurons, among which the fusiform kind predominate significantly (P<0.001), and a lateral region with larger neurons, with significantly (P<0.001) more triangular cells. Neurons in the medial region show a characteristic and strong (P<0.001) tendency for their dendrites to be oriented toward the lumen of the aqueduct, and through them the physiologically active substances of the CSF may influence the functional activity of neurons of PGM.Central Research Institute of Reflex Therapy, Moscow City Council Main Health Board, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 773–777, November–December, 1984.     

Connections of the corticospinal and rubrospinal tracts with neurons of the cervical spinal cord in cats

The distribution of focal potentials over the cross section of the 7th cervical segment of the spinal cord was studied during stimulation of the pyramids, the red nucleus, and a peripheral nerve (ulnar) in adult cats anesthetized with chloralose and Nembutal. The earliest focal potentials in the fasciculus dorsolateralis were recorded 1.4–1.5 msec after stimulation of the pyramids and 0.8–0.9 msec after stimulation of the red nucleus. These times correspond to maximal condution velocities of 56–68 and 105–124 m/sec respectively. The earliest post-synaptic activity in response to pyramidal stimulation was found in the lateral areas of laminae V and VI, and in response to stimulation of the red nucleus in laminae VI and VII in Rexed's classification. The pyramidal wave also evoked considerable postsynaptic activity in medial areas of the dorsal horn. In response to stimulation of peripheral afferents activity was evoked in neurons in the central and medial parts of laminae V and VI. It is postulated on the basis of these results that corticospinal and rubrospinal fibers may be connected monosynaptically with specialized interneurons, free from peripheral influences, in the lateral areas of laminae V and VII respectively; in the lateral part of lamina VI convergence of both types of influences on the same cells is possible. Interaction between descending and afferent influences possibly takes place on more medially located neurons.A.A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 158–167, March–April, 1972.     

Electrophysiological investigation of the cat ciliary ganglion

Electrical responses of some nerves of the ciliary ganglion to stimulation of its other nerves were recorded, and intracellular recordings were also made from neurons of the ganglion (in situ). The overwhelming majority of preganglionic fibers terminate synaptically on neurons of the ganglion. Postganglionic fibers leave in the lateral and medial ciliary nerves, in which the velocity of conduction of excitation ranges from 1.9 to 9.0 m/sec. A few preganglionic fibers pass through the ciliary ganglion into the lateral ciliary nerve, giving off collaterals to neurons of the ganglion, so that stimulation of the lateral ciliary nerve evokes a response in the medial ciliary nerve (preganglionic axon reflex). The resting potential of neurons of the ciliary ganglion is 57±2.8 mV, and their action potential 68±3.6 mV. Single orthodromic stimulation usually evokes a single action potential in a neuron. The amplitude of the EPSP is increased during hyperpolarization of the postsynaptic membrane, confirming the chemical nature of synaptic transmission in the ganglion. The antidromic response consists of an IS-component and spike. The spike is followed by after-hyperpolarization, with a mean amplitude equal to 31% of the spike amplitude, and the time taken for it to fall to one–third of its initial amplitude is 75–135 msec.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 101–108, July–August, 1969.     

Amino Acid Levels in the Guinea Pig Spinal Gray Matter After Axotomy of Primary Sensory and Descending Tracts

This study attempts to determine if the axonal endings of dorsal root sensory fibers and of descending axons to the spinal gray matter in the guinea pig store glutamate and/or aspartate. Bilateral dorsal rhizotomy (spinal segments C5-T1) and partial cordotomy (segment C5, right side) were used to interrupt primary sensory and descending tracts, respectively. At 1 and 2 days after surgery, amino acid levels were determined in regions microdissected from areas of the gray matter of spinal segment C7 that receive heavy projections from the primary sensory and the descending tracts. These regions were identified by visualizing the degeneration of axons and their terminal fields in silver-impregnated light microscopic preparations of the spinal cord. After dorsal rhizotomy, the heaviest degeneration in the spinal gray appeared centrally in laminae II-IV and medially in laminae IV-VI. The levels of aspartate, glutamate, and gamma-aminobutyrate were reduced by 34, 21, and 26% in laminae II-IV and 28, 33, and 23% in medial laminae IV-VI. The levels of glycine, alanine, and threonine-serine-glutamine (unseparated) were increased. After partial cordotomy, the heaviest degeneration in the spinal gray appeared laterally in laminae IV-VI, dorsolaterally in lamina VII, and in lamina IX. The levels of aspartate and glutamate were reduced by 22 and 28% in lateral laminae IV-VI and by 26 and 28% in dorsolateral laminae VII and IX. Glycine levels were reduced by 9% in dorsolateral laminae VII and IX. The levels of gamma-aminobutyrate, alanine, and threonine-serine-glutamine were either unchanged or raised. These findings suggest that the axonal endings of the primary sensory and of one or more of the descending tracts probably contain relatively high levels of glutamate and aspartate, and that they may use these amino acids as transmitters. The partial deafferentation of spinal interneurons and the destruction of some propriospinal fibers probably caused the losses of gamma-aminobutyrate and glycine, and contributed modestly to those of aspartate.     

Structural features of corticospinal connections in the cat

Structural features of connections between corticospinal fibers and neurons of the cervical and lumbar segments of the cat spinal cord were studied by the experimental degeneration method. It was shown by the Fink-Heimer method that the preterminals of these fibers are mainly located in the lateral part of Rexed's laminae V and VI (the lateral basilar region — LBR) and also, to some extent, in the medial basilar region (MBR). The diameters of the myelinated part of these fibers in LBR vary from 0.8 to 11µ. They form chiefly terminals of the F-type (with flattened synaptic vesicles), which undergo degeneration of the light type (lysis of the internal structures) or, less frequently, the dark type (increase in electron density), followed by phagocytosis by glial cells. No degenerating terminals are found in the glomerulus-like synaptic complexes, in axo-axonal synapses, or on dendrites with a dark matrix. Only a few degenerating axon terminals still remained 20 days or more after extirpation of the cortex. The relative number of terminals of different types was counted at this period. The number of axon terminals of F-type on the dendrites was reduced by 1.5 times, while the number on the soma remained relatively unchanged. The results confirm the earlier hypothesis that corticospinal fibers terminate on dendrites and their appendages in LBR as endings of the F-type. These neurons also receive many terminals from other intracerebral systems.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol.4, No.5, pp. 480–487, September–October, 1972.     

Laminar distribution of sources of ascending spinocerebral fiber systems in the cat spinal cord

The location of labeled neurons that are sources of ascending crossed and uncrossed supraspinal fiber systems was studied in the laminae of gray matter of the spinal cord in 18 cats by the retrograde axonal transport of horseradish peroxidase method. Neurons in the lateral zones of the dorsal horn were shown to make direct, and cells in neighboring regions indirect (through relay nuclei of the dorsal columns) connections with the contralateral thalamus. In the lower segments of the spinal cord sources of crossed spinoreticular and spinothalamic fiber systems are located in the medial regions of the ventral horn and lateral zones of the lateral basilar region. Some large neurons in the motor nuclei were shown to send their axons into the lateral reticular nucleus of the medulla. On the basis of the results a scheme of the laminar organization of sources of ascending fiber systems in the cat spinal cord is constructed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 451–459, September–October, 1979.     

Morphology of the cat auditory cortex

The ultrastructural features of the primary auditory cortex of the cats and the character of the endings of geniculo-cortical afferent fibers in the early stages of experimental degeneration evoked by destruction of the medial geniculate body were studied. In all layers of the cortex asymmetrical synapses with round synaptic vesicles on dendritic spines and on thin dendritic branches of pyramidal and nonpyramidal neurons are predominant. Symmetrical synapses with flattened or polymorphic vesicles are distributed chiefly on the bodies of the neurons and their large dendrites. Because there are few symmetrical synapses which could be regarded as inhibitory it is postulated that inhibitory influences may also be transmitted through asymmetrical synapses with round vesicles. Other types of contacts between the bodies of neurons, dendrites, and glial processes also were found in the auditory cortex. Degenerating terminals of geniculo-cortical fibers were shown to terminate chiefly in layer IV of the cortex on pyramidal and nonpyramidal neurons. Degeneration was of the dark type in asymmetrical synapses with round vesicles. The results are dicussed in connection with electrophysiological investigations of the auditory cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 519–524, September–October, 1973.     

Distribution and ultrastructure of thalamic afferents in the cat auditory cortex

Ultrastructural features of thalamic afferent fibers were studied in the cat auditory cortex in the early stages (on the 4th day) of experimental degeneration produced by destruction of the medial geniculate body. A coordinate grid was used in conjunction with an electron micro-scope to study the topography of the degenerating elements over wide areas of sections, so that the density of degeneration could be determined quantitatively in different layers of the cortex. Degenerating axons were found in all layers. Most of the large (5–7 µ) degenerating axons are located in layer VI; their diameters were smaller in the upper layers of the cortex. Degenerative changes affecting synaptic terminals of thalamo-cortical afferents were of the "dark" type. Fibers of the geniculo-cortical tract were shown to terminate mainly in cortical layer IV. A few degenerating synapses were found in the molecular layer. Terminals with sperical synaptic vesicles are found mainly on the spines of dendrites where they form "asymmetrical" contacts. A few degenerating axo-somatic synapses were observed on stellate neurons in layer IV. The results are discussed in connection with electrophysiological investigations of the cat auditory cortex during stimulation of specific afferent fibers.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 6, pp. 612–620, November–December, 1972.     

Ultrastructural organization of the neuropil in layer I of the cat cerebral cortex

The ultrastructure of layer I in the middle ectosylvian gyrus (area 22) of the cat's cerebral cortex was investigated. Beneath the subpial astrocytic layer most of the neuropil in layer I was shown to be occupied by nerve fibers and their terminals, terminal branches, dendritic spines, and astrocytic processes surrounding them. More than 90% of the presynaptic terminals contained spherical synaptic vesicles. The predominant types of interneuronal junctions are axo-spinous and axo-dendritic synapses of asymmetrical type. Presynaptic terminals, which contain flattened and pleomorphic synaptic vesicles, take part in the formation of all symmetrical junctions, accounting for 6% of the total number of synapses. Large polymorphic outgrowths filled with vacuoles — so-called multivacuolar sacs — are described. These structures were invaginated into varicose expansion of the terminal branches of apical dendrites of pyramidal neurons. They are shown to be outgrowths of presynaptic terminals. Dependence of synaptic function on the shape of the synaptic vesicles is examined.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 15, No. 1, pp. 50–55, January–February, 1983.     

Some morphological and functional properties of the lateral line system of the dwarf catfish

The peripheral and central portions of the lateral line system of the dwarf catfish were studied by morphological and electrophysiological methods. The posterior lateral line nerve, innervating the electro- and mechanoreceptors of the trunk, was shown to consist of poorly myelinated fibers 2–9 µ in diameter. The conduction velocity in this nerve varied from 10 to 15 m/sec. The lateral line nerves end in the medial nucleus of the acoustico-lateral region, which consists of dorsal and medial parts. The former is composed of circular and triangular cells measuring 6–14 µ, the second part by circular cells measuring 4–6 µ. These parts of the medial nucleus are most sharply differentiated in the region of entry of the auditory nerve. Responses to stimulation of the lateral line electro- and mechanoreceptors were recorded over the whole of the acousticolateral region in the caudal-rostral direction. The neurons studied were located at depths of 400–800 µ in the region of the medial nucleus.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad, Translated from Neirofiziologiya, Vol. 7, No. 2, pp. 203–207, March–April, 1975.     

Vasoactive intestinal polypeptide (VIP)-containing neurons: distribution throughout the brain of the chick (Gallus domesticus) with focus upon the lateral septal organ

The distribution of VIP-like perikarya and fibers was determined throughout the chick brain. The most rostral immunoreactive perikarya were found to be cerebrospinal fluid-contacting neurons in the pars medialis of the lateral septal organ. Additional data were presented supporting the idea that the lateral septal organ is another circumventricular organ within the brain of birds (Kuenzel and van Tienhoven 1982). A large group of immunoreactive perikarya was found in the lateral hypothalamic area and appeared continuous with immunoreactive neurons in the anterior medial and ventromedial hypothalamic nuclei (n). A few perikarya were located in the paraventricular hypothalamic n. A number of immunoreactive neurons were found within and about the infundibular and inferior hypothalamic n., none however was immunoreactive cerebrospinal fluid-contacting neurons. Immunoreactive perikarya were found predominantly in laminae 10–11 of the stratum griseum et fibrosum superficiale. A few scattered perikarya were found ventromedial to the n. tegmenti pedunculo-pontinus pars compacta and locus ceruleus. Some of the immunoreactivity was unusual, being very homogeneous within the cell body with little evidence of the material in the axon or dendrites. Perikarya were found in the central gray, n. intercollicularis, and area ventralis of Tsai. The most caudal structure showing immunoreactive neurons was the n. reticularis paragigantocellularis lateralis. Brain areas containing the most abundant immunoreactive fibers, listed from the rostral-most location, were found in the ventromedial region of the lobus parolfactorius and the lateral septal n. Continuing caudally, there were immunoreactive fibers within the periventricular hypothalamic n.; some of the fibers were found to travel for some distance parallel to the third ventricle. Dense immunoreactive fibers were found in the tractus cortico-habenularis et cortico-septalis, medial habenular n. and posterior and dorsal n. of the archistriatum. A number of areas had what appeared to be baskets of immunoreactive fibers (perhaps immunoreactive terminals) surrounding non-reactive perikarya. Brain areas containing terminals included the piriform cortex, area ventralis of Tsai, interpeduncular n., and specific regions of the stratum griseum et fibrosum superficiale. A very dense immunoreactivity occurred within the external zone of the median eminence, the dorsolateral parabrachial n., and n. tractus solitarii. Vasoactive intestinal polypeptide appears to be a useful peptide for defining the neuroanatomical constituents of the visceral forebrain in birds.     

The quantitative morphological characteristics of the neurons of the anterior horns of the spinal cord in the kitten]

Golgi preparations of cervical part of the spinal cord of 30-day kittens were used to study sparely and densely branching neurons of lamina VII, sparely and densely branching neurons of lamina VIII and big densely branching motor neurons (as classified by Leontovich) of medial and lateral regions of lamina IX. Qualitative morphological characteristics of geometry of each cell type were obtained by the method of computerized morphometry. The details of the structure of neurons belonging to different laminae of grey matter are discussed.