Acetylcholine estimate in glial cells of the cat spinal cord

Structures containing acetylcholinesterase were found in the motor nuclei of the cervical enlargement of the cat spinal cord by light and electron microscopy in material stained by the Karnovsky-Roots method. The specific response was observed not only in neurons of the motor nuclei, but also in some satellite cells, astrocytic glial cells, and Schwann cells. A positive reaction for acetylcholinesterase was found in some of the satellite cells located close to both cholinergic and noncholinergic neurons. As a result of electron microscopy, an electron-dense deposit of copper ferrocyanide was found on the structures of the nucleolus, on the surface of the inner and outer layers of the nuclear membrane, in the pores of the nuclear membrane, in the perinuclear space, and in the endoplasmic reticulum of the perikaryon of some satellite cells, as well as on the outer and inner surfaces of the cytoplasmic membrane of the Schwann cells.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev, Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 48–51, January–February, 1977.     

Electron-microscopic analysis of adrenergic nerve endings in the cat caudal mesenteric ganglion

The ultrastructure of nerve endings of the cat caudal mesenteric ganglion was studied after fixation of the material with 4% lithium permanganate solution by Richardson's method in the modification of Hökfelt et al. [12]. This fixation method was shown to permit the demonstration of numerous adrenergic as well as cholinergic nerve endings. Four types of adrenergic organelles were distinguished in neurons of the ganglion: small and large granular vesicles 30–50 and 70–90 nm in diameter, respectively, a tubular reticulum with electron-dense contents, and small granular vesicles 15–20 nm in diameter. The localization of the adrenergic endings and their relations with other processes and cells of the caudal mesenteric ganglion were studied in detail. The problem of the origin and physiological role of adrenergic nerve endings in this ganglion is discussed.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 86–92, January–February, 1980.     

Response of rat hypothalamic perinuclear supraoptic neurons to stimulating the pituitary stalk and hippocampus

Orthodromically activated neurons (OAN) are found in the hypothalamic supraoptic area under pituitary stalk stimulation, differing in their dependence on pattern of orthodromic activation and recording site. More than a half of OAN responded to stimulation of the ventral hippocampus and response was consistently excitatory initially. Some similarity was found between the pattern of response of most OAN to pituitary stalk stimulation. Aspects of hippocampal influence on OAN taking account of their location within the supraoptic nucleus area and the perinuclear zone are examined, as well as their presumed morphofunctional connections with antidromically identified neurosecretory cells.A. A. Ukhtomskii Institute of Physiology, State University, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 596–604, September–October, 1990.     

Projections from the ventral subiculum to supraoptical hypothalamic region neurons not responding to stimulation of the hypophyseal pedunculus

Effects of subiculum stimulation on spike activity of neurons localized in the supraoptical nucleus (SON) and perinuclear region were studied in experiments on rats; special attention was paid to neurons that did not respond to stimulation of the hypophyseal pedunculus. With rare exception, the SON cells did not respond to subiculum stimulation; 47% of neurons in the perinuclear region were activated after subiculum stimulation, whereas in 15% the frequency of spike activity decreased. Some neurons were found in the perinuclear region that responded to subiculum stimulation by antidromic spike generation.Organization of the studied afferent input to neurons of the supraoptical region and probability of interconnections between investigated structures are discussed.Neirofiziologiya/Neurophysiology, Vol. 25, No. 4, pp. 253–257, July–August, 1993.     

Influence of Temocapril on Cultured Ventral Spinal Cord Neurons

Temocapril, a angiotensin-converting enzyme (ACE) inhibitor, was tested for neurotrophic activity in primary explant cultures of ventral spinal cord of fetal rats (VSCC). Temocapril had a remarkable effect on neurite outgrowth with a 4.2- to 5.1-fold increased over that of control VSCC at their effective concentrations. In temocapril-treated VSCC, choline acetyltransferase (ChAT) activity was also increased 2.4–3.2 times over that of control at 10^–9 and 10^–8 M, respectively. Our data suggest that temocapril is a candidate for neurotrophic factors on spinal motor neurons in vitro. A possible therapeutic role for temocapril in damaged motor neurons, such as in motor neuropathy and amyotrophic lateral sclerosis, remains to be defined.     

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.     

Ultrastructure of interneuronal connections in the superior cervical sympathetic ganglion in cats

The structure of interneuronal synapses in the superior cervical sympathetic ganglion was studied in cats under normal conditions and after division of the cervical sympathetic nerves and removal of spinal ganglia T₁₂–L₂. A definite number of dendro-dendritic and dendro-somatic junctions is observed in the ganglion and most of them remained intact after operations of both types; they are probably synapses formed by dendrites of neurons located in the ganglion. Synapses of this sort participate in the formation of nest-like complexes, consisting of consecutive junctions of one neuron with several dendrites. The formation of such complexes may provide the anatomical basis for synchronization of rhythmic neuronal activity in the cellular glomeruli of the ganglion. The results of an ultrastructural study of dendro-dendritic junctions suggests that they are synaptic in nature. Some dendro-dendritic junctions underwent degeneration after both types of operation and are probably endings of neurons in spinal ganglia. Wide club-like structures, probably receptor endings, formed by dendrites of afferent neurons of spinal ganglia, also are found in the ganglion. These structures lie freely in the stoma of the ganglion or form contacts with axon terminals and dendrites of neurons located in the ganglion; some of them degenerate after removal of spinal ganglia T₁₂–L₂.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 299–306, May–June, 1981.     

Study of firing pattern in human soleus motor units in tonic vibration reflex

Tonic vibration reflex was produced in the human soleus muscle by vibrating the tendon at the rate of 30–180 Hz and motor unit potentials were recorded. A correlation was found between the points at which these potentials occurred and vibratory stimuli over lower ranges of vibration rates (of up to 70–80 Hz) in all motor units, indicative of discrete bursts in the synaptic inflow to the motoneuron matching the vibratory stimuli. The correlation disappeared with an increase in vibration rate and manifested at high as well as low vibration rates in voluntarily contracted muscle. Since vibration is known to (presynaptically) depress monosynaptic reflexes induced by activating primary spindle endings, it is suggested and maintained that the correlation found at low vibration rate ranges could result from activating vibrational stimuli of secondary spindle endings which act on motoneurons via short pathways, thus evoking discrete motoneuronal EPSP.Information Transmission Research Institute, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 765–772, November–December, 1989.     

Neuronal organization of the lateral basilar region of the cat spinal cord

The neuronal organization of the lateral basilar region (LBR) of gray matter in the cervical portion of the cat spinal cord was studied by light and electron microscopy. It was found that LBR neurons form a homogeneous group with regard to the size of their soma. The ordinary pale ultrastructure of the cytoplasm is found in 96.8% of neurons examined. The ultrastructure of the cytoplasm of the small cells (3.2%) is dark and their matrix has high electron density. Most endings on LBR neurons have spherical vesicles (of the S-type). Endings with flattened vesicles (F-type) are next in order of numerical frequency. In some endings, besides the ordinary synaptic vesicles, there are other vesicles with an osmiophilic center, and endings with a dense matrix and numerous spherical vesicles. Endings of the F-type are relatively more numerous on dendrites of LBR neurons than on their soma. Axodendritic synapses form 87.8% of the synaptic connections of the LBR, and axo-somatic synapses 9.2%. The few axo-axonal synapses are formed by small endings with small synaptic vesicles and large plaques with spherical vesicles. The latter frequently make contact with several dendrites simultaneously. The functional role of the various neuronal structures of LBR in the transmission of descending and afferent influences is discussed.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. 3, pp. 296–302, May–June, 1972.     

Morphological characteristics of callosal neurons of the cat primary auditory cortex (AI)

Cortical stratification of neurons forming callosal projections to the primary cortical area (AI) was investigated in cats using horseradish peroxidase axonal transport techniques. The population of area AI callosal neurons was found to be composed of several groups of cells. The group comprising around 60% of all callosal neurons of this area consists of large layer III pyramidal neurons. Callosal neurons belonging to this layer have a mean perikaryon profile area of 261.8±8.2 µm²; they account for 22% of all cells found in the layer. The second group, comprising 27% of all area AI callosal neurons, was largely made up of large layer V and VI cells; these could not be classed as pyramidal neurons due to the shape of their somata and the geometry of their dendritic arborization. Perikaryon profile in these nonpyramidal neurons occupied an area of 250.3±8.4 µ². No callosal neurons were observed in layer I. These account for 6 and 7% of total numbers of callosal neurons of area AI in layers II and IV. Callosal neurons were found to form projections to all layers of area AI in the contralateral hemisphere. Highest density of callosal fiber endings was observed in layers II and III.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 249–256, March–April, 1990.     

Investigation of habituation reaction of neurons of the cat motor cortex

The neuronal and total surface activity of the cortical representation of the motor analyzer in the region of the posterior sigmoid gyrus of the cat brain in response to rhythmical light, sound, and electrical stimuli and their complexes was analyzed. Two groups of neurons were found, of which the first is characterized by a gradual decrease in the number of peaks in the response and by their subsequent disappearance and the second by the absence of a discharge in response to stimulation and by its development before the application of the next stimulus. The first group was comprised of neurons which do not have background activity and the second was made up of neurons with a background activity of 0.4–3.7 imp/sec. This reorganization of the activity of cortical neurons in response to rhythmical stimulation is considered to be a habituation phenomenon.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 245–251, May–June, 1971.     

Electron microscopic observations on synapse-like contacts between pituicytes and different types of nerve fibers in the anuran pars nervosa

Summary Pituicytes of Rana pipiens could be classified into two types, pale and dense, according to their relative densities of cytoplasm and the populations of free ribosomes and cell organelles. An intermediate type of pituicyte was also recognized.Lipid droplet such as are typical in the cytoplasm of mammalian pituicytes, are not in the cytoplasm of either types of frog pituicyte. Both types have long cytoplasmic processes which run among the nerve fibers, and some of them end at the pericapillary space.Nerve endings making synapse-like contacts with the cell bodies or the processes of the pituicyte are frequent. According to the structures and sizes of granules and vesicles in the nerve endings, these endings are classified into one of three types: 1) A, which appears to be a peptidergic neuronal ending containing dense granules 1,200–2,000 Å in diameter and small clear vesicles 300–400 Å in diameter; 2) B, which appear to be monoaminergic endings containing cored vesicles 600–1,000 Å in diameter and small clear vesicles 300–500 Å in diameter; 3) C, which appear to be cholinergic endings containing only small clear vesicles. Type C endings are relatively rare. In the synaptic area the axonal membranes appose those of the pituicytes across a gap of about 200 Å and numerous presynaptic vesicles are clustered or accumulated near the presynaptic membranes.The author wish to express his hearty thanks Professor Dr. A. Gorbman, Zoology Department, University of Washington, Seattle, U.S.A. and Professor Dr. H. Fujita for their helpful advices and criticisms. The frog tissues were obtained and fixed in Professor A. Gorbman's laboratory supported by U.S.P.H.S. grant NS 04887.     

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.     

Lobula plate and ocellar interneurons converge onto a cluster of descending neurons leading to neck and leg motor neuropil in Calliphora erythrocephala

Summary In the fly, Calliphora erythrocephala, a cluster of three Y-shaped descending neurons (DNOVS 1–3) receives ocellar interneuron and vertical cell (VS4–9) terminals. Synaptic connections to one of them (DNOVS 1) are described. In addition, three types of small lobula plate vertical cell (sVS) and one type of contralateral horizontal neuron (Hc) terminate at DNOVS 1, as do two forms of ascending neurons derived from thoracic ganglia. A contralateral neuron, with terminals in the opposite lobula plate, arises at the DNOVS cluster and is thought to provide heterolateral interaction between the VS4–9 output of one side to the VS4–9 dendrites of the other. DNOVS 2 and 3 extend through pro-, meso-, and metathoracic ganglia, branching ipsilaterally within their tract and into the inner margin of leg motor neuropil of each ganglion. DNOVS 1 terminates as a stubby ending in the dorsal prothoracic ganglion onto the main dendritic trunks of neck muscle motor neurons. Convergence of VS and ocellar interneurons to DNOVS 1 comprises a second pathway from the visual system to the neck motor, the other being carried by motor neurons arising in the brain. Their significance for saccadic head movement and the stabilization of the retinal image is discussed.     

Investigation of a monosynaptic excitatory connection by means of a biomathematical model of neuronal interaction

A biomathematical model of neuronal interaction, including real mollusk neurons and mathematical models of functioning of deficient synaptic connections between these neurons and synaptic endings of other neurons, was created on the basis of a computer and an experimental arrangement for investigating molluscan ganglia. The effect of the properties of a monosynaptic excitatory connection of the statistical characteristics of spike trains of interacting pacemaker neurons was investigated.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 413–420, July–August, 1980.     

Effects of cholinergic compounds on spontaneous quantal transmitter release at the frog neuromuscular junction

The effects of nicotinic and muscarinic mimetics and lytics on spontaneous quantal transmitter secretion from the motor nerve endings were investigated during experiments on theRana temporaria sartorius muscle. Acetylcholine and carbachol reduced the frequency of miniature endplate potentials both in a normal ionic medium and in one with potassium ion concentration raised to 10 mM. Similar effects were produced by nicotinic agonists, namely nicotine, tetramethylammonium, and suberyldicholine, whereas muscarinic mimetics — methylfurmetide, oxotremorine, and F-2268 (L- and D-stereoisomers) — did not affect transmitter release. Neither d-tubocurarine, benzohexonium, nor atropine abolished the presynaptic effects of carbachol and acetylcholine. It is concluded that nicotinic cholinoreceptors are present at the frog motor nerve endings which modify spontaneous transmitter release and differ in their pharmacological properties from recognized N-cholinoreceptors of the motor and autonomic systems of the higher vertebrates.S. V. Kurashov Medical Institute, Ministry of Public Health of the RSFSR, Kazan'. Translated from Neirofiziologiya, Vol. 18, No. 5, pp. 586–593, September–October, 1986.     

Neuronal responses of the reticular and anterior ventral thalamic nuclei to stimulation of the thalamic ventrolateral nucleus and motor cortex

Responses of 137 neurons of the rostral pole of the reticular and anterior ventral thalamic nuclei to electrical stimulation of the ventrolateral nucleus and motor cortex were studied in 17 cats immobilized with D-tubocurarine. The number of neurons responding antidromically to stimulation of the ventrolateral nucleus was 10.5% of all cells tested (latent period of response 0.7–3.0 msec), whereas to stimulation of the motor cortex it was 11.0% (latent period of response 0.4–4.0 msec). Neurons with a dividing axon, one branch of which terminated in the thalamic ventrolateral nuclei, the other in the motor cortex, were found. Orthodromic excitation was observed in 78.9% of neurons tested during stimulation of the ventrolateral nucleus and in 52.5% of neurons during stimulation of the motor cortex. Altogether 55.6% of cells responded to stimulation of the ventrolateral nucleus with a discharge of 3 to 20 action potentials with a frequency of 130–350 Hz. Similar discharges in response to stimulation of the motor cortex were observed in 30.5% of neurons tested. An inhibitory response was recorded in only 6.8% of cells. Convergence of influences from the thalamic ventrolateral nucleus and motor cortex was observed in 55.7% of neurons. The corticofugal influence of the motor cortex on responses arising in these cells to testing stimulation of the ventrolateral nucleus could be either inhibitory or facilitatory.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 460–468, September–October, 1978.     

Role of the midbrain periaqueductal gray matter in conditioned reflexes

Unit activity in the midbrain periaqueductal gray matter (PGM) during an instrumental placing reflex, its extinction, differentiation, and conditioned inhibition, was studied in chronic experiments on cats. Spike responses 1–2 sec in duration in 69 (36.7%) of 182 neurons preceded by 400–800 msec the beginning of conditioned-reflex and voluntary intertrial movements. These advanced responses appeared 200 msec before the corresponding advance responses of motor cortical neurons. Fifty-eight neurons (30.9%) responded directly to acoustic stimulation with a latent period of 10–50 msec for 2–6 sec, 19 neurons (10.1%) generated double responses, linked with both the acoustic stimulus and subsequent conditioned-reflex movement, and 42 neurons (22.3%) did not respond to acoustic stimulation, although individual neurons of this group changed the level of their spontaneous activity in response to repeated conditioned stimulation, and this change was maintained for some tens of minutes. Extinction, differentiation, and conditioned inhibition all abolished conditioned-reflex movements, but each type of internal inhibition was accompanied by its own characteristic changes in the firing pattern of PGM neurons. Functional independence of neurons of the first and second groups was demonstrated during extinction and recovery of the conditioned-reflex. The results indicate the important role of PGM not only in the mechanism of the conditioned reflex, but also in the development of its internal inhibition.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 3, pp. 403–419, May–June, 1984.     

Action of precursors of noradrenaline synthesis on membrane receptors of chick embryo spinal neurons

Effects of noradrenaline precursors on glycine and N-methyl-D-aspartate (NMDA) receptors in spinal cord neurons recently isolated from chick embryo were investigated using whole cell patch-clamp and concentration clamp techniques. Both L-alanine and L-DOPA were found to be glycine agonists capable of potentiating NMDA response, while L-tyrosine does not activate glycine but can potentiate NMDA response. Lastly, L-phenylalanine and dopamine do not interact with either glycine or NMDA receptors.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 665–670, September–October, 1990.     

Participation of midbrain periaqueductal gray matter in defense conditioning in rats

Responses of neurons of the periaqueductal gray matter (PAG) were studied in chronic experiments on cats during formation and extinction of a defensive conditioned reflex to sound and its differential inhibition. In response to conditioned stimulation these neurons developed phasic-tonic spike responses up to 3 sec in duration. During combination of stimuli these responses were formed long before the conditioned reflex and disappeared long after the latter was extinguished. In the case of an established conditioned reflex, the onset of spike responses occurred 100–200 msec before the appearance of motor responses. An increase in spike activity of tonic character in neurons of PAG preceded voluntary movements by 100–500 msec. The responses of these neurons to presentation of a differential stimulus consisted of groups of spikes 150–200 msec in duration. They were formed with difficulty, and their manifestation was made even more difficult by an interruption during the experiment and by preceding positive stimuli. On the basis of the results a conditioned reflex can be regarded as the result of a multilevel hierarchic process of readjustment of unit activity, which begins in the nonspecific structures of the midbrain.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 15, No. 3, pp. 278–287, May–June, 1983.