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.     

Sources of cortical,hypothalamic and spinal serotonergic projections: Topical organization in the dorsal raphe nucleus

A study was made of retrograde axon transport of luminescent stains (primulin, fluoro-gold, fast blue, and nuclear yellow) from the spinal cord, the frontal cortex and lateral hypothalamus to various neuron groups of the periventricular gray matter of the midbrain and the dorsal tegmentum of the pons Varolii. Two large groups of serotonergic neurons are localized in the dorsomedial area of the dorsal raphe nucleus where projections to the thoracic segments of the spinal cord originate. Some of these neurons form divergent axon collaterals to the frontal cortex. Our data indicate that the antinociceptive effect of stimulating the "purely analgesic zone" of the midbrain periventricular gray matter may be due to direct involvement of the dorsal raphe nucleus in the descending control of impulsation induced by nociceptive stimulation at the spinal cord level. The neurotransmitter and neuromodulator role of separate cortical and hypothalamic projections of serotonin-containing neurons in the dorsal raphe nucleus is discussed.A. M. Gorky Medical Institute, Donetsk. A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 1, pp. 87–96, January–February, 1992.     

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.     

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.     

The shortened spinal cord in tetraodontiform fishes

In teleosts, the spinal cord generally extends along the entire vertebral canal. The Tetraodontiformes, in which the spinal cord is greatly reduced in length with a distinct long filum terminale and cauda equina, have been regarded as an aberration. The aims of this study are: 1) to elucidate whether the spinal cord in all tetraodontiform fishes shorten with the filum terminale, and 2) to describe the gross anatomical and histological differences in the spinal cord among all families of the Tetraodontiformes. Representative species from all families of the Tetraodontiformes, and for comparison the carp as a common teleost, were investigated. In the Triacanthodidae, Triacanthidae, and Triodontidae, which are the more ancestral taxa of the Tetraodontiformes, the spinal cord extends through the entire vertebral canal. In the Triacanthidae and Triodontidae, the caudal half or more spinal segments of the spinal cord, however, lack gray matter and consist largely of nerve fibers. In the other tetraodontiform families, the spinal cord is shortened forming a filum terminale with the cauda equina, which is prolonged as far as the last vertebra. The shortened spinal cord is divided into three groups. In the Ostraciidae and Molidae, the spinal cord tapers abruptly at the cranium or first vertebra forming a cord‐like filum terminale. In the Monacanthidae, Tetraodontidae, and Diodontidae, it abruptly flattens at the rostral vertebrae forming a flat filum terminale. The spinal cord is relatively longer in the Monacanthidae than that in the other two families. It is suggested by histological features of the flat filum terminale that shortening of the spinal cord in this group progresses in order of the Monacanthidae, Tetraodontidae, and Diodontidae. In the Balistidae and Aracanidae, the cord is relatively long and then gradually decreased in dorso‐ventral thickness. J. Morphol. 276:290–300, 2015. © 2014 Wiley Periodicals, Inc.     

Ultrastructural characteristics of dendrites of spinal neurons

A qualitative and quantitative analysis of outgrowths from the surface membrane of dendrites in regions of the gray matter of the spinal cord where different long descending tracts terminate was undertaken by electron microscopy. These outgrowths of dendrites were found to be most simply organized in the medial part of the ventral horn, where synaptic endings of fibers of the medial lemniscus are concentrated. In the dorsal regions of gray matter, where fibers of the lateral systems terminate, the outgrowths have a more complex structural organization, expressed as changes in size and shape and also as the appearance of elements of a weakly developed spinous apparatus in the matrix. These outgrowths were described as spine-like. A statistically significant difference was found between the size of dendritic outgrowths in the lateral part of Rexed's lamina V and the lateral part of laminae VI–VII, and also the medial part of lamina VIII.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 3, pp. 271–277, May–June, 1978.     

Effects of partial bulbar section on inhibition of jaw-opening reflexes induced by central gray matter stimulation in the cat

The effects of severing the spinal trigeminal tract and its caudal nucleus on high-threshold jaw-opening reflex elicited by tooth pulp stimulation were investigated during experiments on cats under chloralose-Nembutal anesthesia. Low-threshold jaw-opening reflex produced by stimulating the A--infraorbital nerve at an intensity 2–3 thresholds in relation to the most excitable fibers on this nerve was also observed, as well as suppression of these reflexes induced by central gray matter stimulation. It was found that spinal trigeminal tract section produces a 8–52% increase in high-threshold reflex. The amplitude of low-threshold reflex either remained unchanged or showed a slight tendency to rise or fall. Brief stimulation of the central gray matter produced a 100% decrease in high-threshold reflex in intact animals compared with a 40–60% decrease after section of the trigeminal tract. Protracted stimulation of the central gray brought about an 80% decline in high-threshold reflex in intact animals as against 25–30% after section. The degree to which brief stimulation of the central gray produced depression of low-threshold stimulation remained unchanged by trigeminal tract section. Protracted stimulation of the central gray matter brought about a 25–50% reduction in low-threshold reflex in intact animals and a reduction of 75% in three animals and 15–20% in four animals. This implied that the caudal nucleus of the spinal trigeminal tract exerts a more substantial influence on the process of high- than low-threshold reflex inhibition when the central gray matter is stimulated.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 362–368, May–June, 1987.     

A technique for decalcification and demonstration of substance P-like immunoreactivity

Substance P-like immunoreactivity (SPLI) was demonstrated in mouse spinal cord by an indirect immunofluorescence method after decalcification of the vertebra with a mixture of EDTA and Zamboni's fixative. SPLI was observed mainly in the gray matter of the spinal cord, especially the superficial layers of the dorsal horn; the distribution was the same as in the control spinal cord. No diffusion and depletion of SPLI were recognized after decalcification and no specific fluorescence was observed. The findings reported here indicate that decalcification with a mixture of EDTA and Zamboni's fixative is a useful method for examining SPLI in nervous tissue surrounded in situ by calcified tissues.     

A Technique for Decalcification and Demonstration of Substance P-Like Immunoreactivity

Substance P-like immunoreactivity (SPLI) was demonstrated in mouse spinal cord by an indirect immunofluorescence method after decalcification of the vertebra with a mixture of EDTA and Zamboni's fixative. SPLI was observed mainly in the gray matter of the spinal cord, especially the superficial layers of the dorsal horn; the distribution was the same as in the control spinal cord. No diffusion and depletion of SPLI were recognized after decalcification and no specific fluorescence was observed. The findings reported here indicate that decalcification with a mixture of EDTA and Zamboni's fixative is a useful method for examining SPLI in nervous tissue surrounded in situ by calcified tissues.     

Spread of a neurotropic coronavirus to spinal cord white matter via neurons and astrocytes.

Mouse hepatitis virus strain JHM (MHV-JHM) causes a chronic encephalomyelitis in susceptible mice, with histological evidence of demyelination in the spinal cord. After intranasal inoculation, virus spreads retrogradely to several brain structures along neuroanatomic projections to the main olfactory bulb. In the absence of experimental intervention, mice become moribund before the spinal cord is infected. In this study, infusions of anti-MHV neutralizing monoclonal antibodies were administered to protect mice from the MHV-JHM-induced acute encephalitis and to allow survival until virus spread to the spinal cord. Under these conditions, virus was observed to enter specific layers (primarily laminae V to VII) in the gray matter of the upper spinal cord, consistent with transneuronal spread. While the brain structures which are the sources for virus spread to the spinal cord cannot be determined with certainty, the ventral reticular nucleus is likely to be important since it is consistently and extensively labeled in all mice and receives projections from subsequently infected areas of the spinal cord. After initial entry into the gray matter, virus rapidly spread to the white matter of the spinal cord. During the early stages of this process, extensive infection of astrocytes was noted, suggesting that cell-to-cell spread via these glial cells is an important part of this process. Reports from other laboratories using cultured cells strongly suggested that astrocytes serve as important regulators of oligodendrocyte function and, by extrapolation, have a major role in vivo in the processes of both demyelination and remyelination. Thus, our results not only outline the probable pathway used by MHV-JHM to infect the white matter of the spinal cord but also, with the assumption that infection of astrocytes leads to subsequent dysfunction, raise the possibility that infection of these cells contributes to the demyelinating process.     

Changes in electrical activity of spinal cord neurons in adrenalectomized rats under the effects of corticosteroid hormones

The effects of glucocorticoid (dexamethasone) and mineralocorticoid (deoxycorticosterone) hormones on electrical excitability of nerve cells belonging to the dorsal and ventral horns of the spinal cord induced by stimulating the sciatic nerve, as well as background and evoked activity in single dorsal horn cells were investigated during experiments on adrenalectomized spinal rats using intracellular techniques for recording potential. Both hormones were found to produce mainly facilitatory effects in adrenalectomized animals, manifesting in increased background activity rates in single cells and higher amplitude of field potentials in nerve cells of the dorsal half of the spinal cord. It was shown that neuronal response followed different patterns in the ventral half of the spinal cord gray matter under the action of gluco- and mineralocorticoids: dexamethasone and deoxycorticosterone respectively increased and reduced the amplitude of field potentials in the motoneuronal region. Findings indicate the modulatory influence of adrenal cortical hormones on the electrical activity of spinal cord neurons.Institute of Experimental Biology, Academy of Sciences of the Armenian SSR, Erevan. I. A. Orbeli Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 233–238, March–April, 1989.     

CNS Cell Distribution and Axon Orientation Determine Local Spinal Cord Mechanical Properties

Mechanical signaling plays an important role in cell physiology and pathology. Many cell types, including neurons and glial cells, respond to the mechanical properties of their environment. Yet, for spinal cord tissue, data on tissue stiffness are sparse. To investigate the regional and direction-dependent mechanical properties of spinal cord tissue at a spatial resolution relevant to individual cells, we conducted atomic force microscopy (AFM) indentation and tensile measurements on acutely isolated mouse spinal cord tissue sectioned along the three major anatomical planes, and correlated local mechanical properties with the underlying cellular structures. Stiffness maps revealed that gray matter is significantly stiffer than white matter irrespective of directionality (transverse, coronal, and sagittal planes) and force direction (compression or tension) (K_g= ∼130 Pa vs. K_w= ∼70 Pa); both matters stiffened with increasing strain. When all data were pooled for each plane, gray matter behaved like an isotropic material under compression; however, subregions of the gray matter were rather heterogeneous and anisotropic. For example, in sagittal sections the dorsal horn was significantly stiffer than the ventral horn. In contrast, white matter behaved transversely isotropic, with the elastic stiffness along the craniocaudal (i.e., longitudinal) axis being lower than perpendicular to it. The stiffness distributions we found under compression strongly correlated with the orientation of axons, the areas of cell nuclei, and cellular in plane proximity. Based on these morphological parameters, we developed a phenomenological model to estimate local mechanical properties of central nervous system (CNS) tissue. Our study may thus ultimately help predicting local tissue stiffness, and hence cell behavior in response to mechanical signaling under physiological and pathological conditions, purely based on histological data.     

Upregulation of Vascular Endothelial Growth Factor Receptor-3 in the Spinal Cord of Lewis Rats with Experimental Autoimmune Encephalomyelitis

We investigated the spatiotemporal expression of vascular endothelial growth factor receptor–3 (VEGFR-3) in the spinal cord of Lewis rats with experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. VEGFR-3 mRNA and protein were constitutively expressed in gray matter neurons and in a few white matter astrocytes. Induction of VEGFR-3 occurred predominantly in perivascular infiltrated macrophages in the spinal cord white matter during the inductive phase of EAE. VEGFR-3 expression was also induced in activated microglial cells in the gray and white matter, mainly in the peak phase. In addition, reactive astrocytes in the white matter, but not in the gray matter, expressed VEGFR-3 as disease severity increased. These data suggest that VEGFR-3 is involved in the recruitment of monocytic macrophages and in glial reactions during EAE.     

Age,Gender and Normalization Covariates for Spinal Cord Gray Matter and Total Cross-Sectional Areas at Cervical and Thoracic Levels: A 2D Phase Sensitive Inversion Recovery Imaging Study

The source of inter-subject variability and the influence of age and gender on morphometric characteristics of the spinal cord, such as the total cross-sectional area (TCA), the gray matter (GM) and white matter (WM) areas, currently remain under investigation. Understanding the effect of covariates such as age, gender, brain volumes, and skull- and vertebra-derived metrics on cervical and thoracic spinal cord TCA and GM areas in healthy subjects would be fundamental for exploring compartment specific changes in neurological diseases affecting the spinal cord. Using Magnetic Resonance Imaging at 3T we investigated 32 healthy subjects using a 2D phase sensitive inversion recovery sequence and we measured TCA, GM and WM areas at 4 cervical and thoracic levels of the spinal cord. We assessed age and gender relationships of cord measures and explored associations between cord measures and a) brain volumes and b) skull- and vertebra-derived metrics. Age and gender had a significant effect on TCA, WM and GM areas (with women and elderly having smaller values than men and younger people respectively), but not on the GM area/TCA ratio. The total intracranial volume and C3 vertebra dimensions showed the highest correlations with cord measures. When used in multi-regression models, they reduced cord areas group variability by approximately a third. Age and gender influences on cord measures and normalization strategies here presented might be of use in the study of compartment specific changes in various neurological diseases affecting the spinal cord.     

Properties of axons of sympathetic preganglionic neurons in the cat lumbar spinal cord

Responses arising in ventral root filaments and antidromic discharges of single sympathetic preganglionic neurons in the lateral horn of gray matter in segment L₂ of the cat spinal cord were recorded during stimulation of the white rami communicantes in the same segment. Conduction velocities, thresholds, and refractory periods were determined for individual groups of sympathetic preganglionic fibers. Excitation was conducted more slowly along the intramedullary part of the axons of some sympathetic neurons than along the extramedullary part. In a third group of neurons studied the second antidromic discharge appeared in response to paired stimulation if the interstimulus interval was appreciably longer than their refractory period. It is postulated that axons of sympathetic preganglionic neurons in the lumber spinal cord have a thin intramedullary part and are supplied with recurrent collaterals.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 6, No. 2, pp. 143–151, March–April, 1974.     

On the vegetative network of guinea pig thoracic spinal cord

Summary A dense AChE-positive network was visualized by light microscopy in the thoracic spinal cord of grown-up guinea pigs of both sexes (bodyweight 250–300 g). This network connects in a horizontal and vertical direction the preganglionic sympathetic nuclei (n. intermediolateralis pars principalis (ILp), n. intermediolateralis pars funicularis (ILf), n. intercalatus spinals (IC), n. intercalatus pars paraependymalis (ICpe), (Petras and Cummings, 1972) all along the thoracic spinal cord. In addition to AChE activity, the bundles of fibers of this network also show a strong formaldehyde-induced NA fluorescence.Electron microscopy demonstrated granular vesicles in the cytoplasm of ILp cells. The surface of the ILp and IC neurons is almost entirely covered with synaptic buttons which have clear and granulated synaptic vesicles. The bundles of fibers consists of parallel myelin-free axones and dendrites. On their cource the axones form varicosities. In the varicosities and in the synaptic enlargements there are also clear and granulated (40–100 nm) vesicles. The probable origin of the vegetative network fibers of guinea pig thoracic spinal cord is discussed.     

Muscle tissue changes in vertebrogenic myofascial syndromes

Asymmetrical electrical activity of paired deep segmentary (short) muscles of the back at the level of a vertebra rotation subluxation was found in 50 patients with early neurological thoracic column osteochondrosis (recorded with point electrodes). The proposed experimental simulation of spinal column osteochondrosis (rotation subluxation of the second thoracic vertebra in rabbit) establishes the presence of persistent tonic activity of the deep short paired back muscles at the level of the subluxation and exposes the dynamics of ultrastructural change in the muscle group. Persistent excitation irritation in that segment of the spinal cord and disorganization of deep short back muscle function are associated with over-stretching of richly innervated soft tissues of the same dislocating segment.Scientific-Research Laboratory Center, A. A. Bogomolets Medical Institute, Ukrainian Public Health Ministry, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 3, pp. 298–306, May–June, 1992.     

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.     

Localization of substance P-like immunoreactive fibers in the thoracic spinal cord of guinea pig

Summary A dorsal-horn fiber system is revealed in the thoracic spinal cord of guinea pig by means of substance P immunocytochemistry. This system has repeated craniocaudal and/or caudo-cranial extensions and possesses five main components: (1) a superficial network, situated beneath the dorsolateral surface of the spinal cord. This network is connected with the dorsal root fibers and the accumulations of substance P-like immunoreactive (SP-LI) fibers in the Lissauer's tract; (2) an accumulation of SP-LI fibers in the Lissauer's tract at the border of the dorsal horn; (3) two collateral SP-LI fascicles (one lateral and one medial) emerging from the SP-LI fiber accumulation in the Lissauer's tract; (4) a transversal fascicle running through laminae III–V, and (5) an SP-LI network in the region of the lateral spinal cord nucleus. These components of the dorsal-horn fiber system show widespread connections with ipsi-and contralateral spinal cord areas, connecting them in cranio-caudal and/or caudo-cranial directions. The SP-LI dorsal-horn system has close relationship with groups of preganglionic sympathetic cells in the intermediate zone of the spinal cord, respective with the vegetative network of this zone. It is suggested that some fibers of the dorsal-horn system that originate from dorsal-root ganglia may represent primary sensory or visceral afferents. It is likely that the dorsal-horn fiber system and the vegetative network of the thoracic spinal cord may represent the morphological basis for the integration of (1) the central and peripheral vegetative nervous systems, and (2) the somatic and vegetative nervous system.