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V P Lebedev

Publications and source records attributed to V P Lebedev.

At least 73 records · Page 4Linked to original sources
PubMed1978

[Further study of the descending sympathoactivating pathways of the dorsolateral funiculus of the spinal cord].

The localization and conduction velocities of descending pathways which activate the different groups of sympathetic preganglionic nerons were studied in the cat cervical spinal cord. Certain evidences have been obtained that the fibres located near the dorsal surface of the dorsolateral funiculi with conduction velocities about 24--29 m/sec. can activate the ventral horn preganglionic neurons monosynaptically. In contrast to previous ideas, the sympathetic preganglionic neurons of the lateral horns seem to be activated not by different but by a single group of descending fibers with the conduction velocity 4--8.9 m/sec and localization in more ventral portions of the dorsolateral funiculus. The transmission from these fibers to the sympathetic preganglionic neurons of the lateral horns occurs in two ways: oligosynaptically (probably, disynaptically) and polysynaptically through a more complicated interneuronal chain. The sympathetic preganglionic neurons with unmyelinated axons, localized in the intermediate zone, for the first time were shown to be activated polysynaptically, probably via the same ways as the lateral horn neurons.

Animals↗
PubMed1977

[Convergence of preganglionic fibers on the vasomotor neurons of the sympathetic ganglia of cats].

By means of intracellular recordings from the neurons of isolated lumbar ganglia III-IV it is shown that B1-, B2- and C-preganglionic fibres widely converge on these neurons. The neurons antidromically activated by stimulation of muscular and cutaneous branches were identified as vasomotor ones. The latter had distinct features of preganglionic fibre convergence. Only B2- and C-preganglionic fibres were able to activate them, but the efficacy of the B2-fibres excitatory action was considerably higher. The vasomotor neurons had a lower conduction velocity in its axons (0.95 +/- 0.05 m/s) as compared to other postganglionic neurons (1.30 +/- 0.15 m/s).

Animals↗
PubMed1977

[Relationship between the early and late components of the somato-sympathetic reflex recorded in pre- and postganglionic sympathetic nerves].

In anesthetized cats, the somato-sympathetic reflex was recorded in T3 white ramus and in the lower cardiac nerve during stimulation of intercostal nerves of the T3 and T5 segments. The amplitude of the early response in the preganglionic nerve was considerably higher than the amplitude of the late response, while the reverse was true for the postganglionic nerve. After transection of the spinal cord in the C4-5 level, the late responses were observed both in the lower cardiac nerve and in T3 white ramus. The late response seems to be realisable by the spinal structures. Active role of sympathetic ganglion in transmission of impulses from the spinal cord to effectors, was noted.

Animals↗
PubMed1977

[Recurrent inhibition of the sympathetic pregnaglionic neurons of the lateral horns of the spinal cord].

32.5% of the lateral horn sympathetic preganglionic neurons (B2-SPN) recorded in T3, T8-9 and L2 spinal segments of anaesthetized and immobilized cats were able to respond antidromically to repeated stimuli with time interval (16 ms and more) considerably exceeding the refractoriness of these neurons. This effect was not associated with axonal subnormality. A prolonged time interval between antidromic discharges correlated with the ability of orthodromic spikes to inhibit the generation of antidromic discharges throughout the same period which was substantially longer than the possible collision time. Preceding antidromic activation of a fraction of the described neurons partly inhibited the responses of other neurons in this segment elicited by stimulation of segmental nerves or spinal descending pathways. These data indicate that certain lateral horn sympathetic preganglionic neurons have a recurrent inhibitory mechanism.

Animals↗
PubMed1977

[Neuronal organization of ganglia in the lumbar region of the cat sympathetic chain].

Neuronal organization of the isolated III--VI ganglia in the lumbar sympathetic chain of the cat was studied by means of intracellular recording. Most of the ganglionic neurons (66%) receive synaptic inputs simultaneously from sympathetic B1-, B2- and C-preganglionic fibres (conduction velocity 12.0 +/- 0.7; 4.4 +/- 0.3 and 1.0 +/- 0.1 m/s respectively). The rest of neurons are activated only by fast-conducting B1- and B2-fibres (24%) or only by slow-conducting C-fibres (10%). The main preganglionic input to the ganglionic neurons comes through the white rami of the rostral segments, the less effective inputs--through the other ones. A part of neurons receive preganglionic C-fibres coming into the ganglia through the grey rami.

Animals↗
PubMed1976

[Features of individual sympathetic preganglionic neurons and their axons in the superior thoracic portion of the spinal cord].

The existence of B- and C-preganglionic fibers in T3 spinal cord segment was shown with the aid of recording the antidromic waves in the ventral root filaments elicited by corresponding white ramus stimulation. Conduction velocity, excitability, and refractory period of these fibers were obtained. Antidromic discharges of sympathetic preganglionic neurons with high-speed B-axons were found in ventral horn. Sympathetic preganglionic neurons of the lateral horn have B-axons with slower conduction velocity, and those situated in lateral part of the intermediate zone have C-axons.

Animals↗
PubMed1976

[Responses in the superior thoracic white rami communicantes to stimulation of the dorsolateral funiculi of the spinal cord].

In anesthetized cats, the responses in T3 white rami to stimulation of the spinal dorsolateral funiculi at C5 level displayed three typical waves. The short latency first wave is the result of stimulation of descending fibres with conduction velocity over 20 m/sec, which activate some sympathetic preganglionic neurons monosynaptically. These neurons are, probably, outside of the lateral horns and have axons with conduction velocities over 10 m/sec. The second wave is associated with the discharges of lateral horn's sympathetic preganglionic neurons disynaptically activated by descending fibres with conduction velocity about 6 m/sec.

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PubMed1975

[Polysynaptic components of the early somato-sympathetic reflex response in the lumbar white rami communicantes].

The second and third components of early somatosympathetic relfex discharge were studied in anesthetized cats. Polysynaptic components of the early somatosympathetic and propriospinal somatosomatic discharges were compared. Evidence was found that these reflexes have both common and specialized interneurons in their central polysynaptic chains. It is suggested that the components of the early somatosympathetic reflex are formed by different types of sympathetic preganglionic neurons, namely the second component by neurons of the lateral horns and the third one--by neurons detected in the lateral part of intermediate zone (axonal velocity less than 1.5 m/s). A classification of sympathetic preganglionic neurons is presented.

Animals↗
PubMed1975

[An electron microscopic study of the intermediolateral nucleus of the cat spinal cord].

The intermedio-lateral nucleus in the 1--2 lumbar segments of spinal cord was studied in adult cats. Many large presynaptic terminals contained both the filaments and the light synaptic vesicles which were in contact either with neuronal body or with initial portions of dendrites. There were no spines on the dendrites. The nucleus was shown to contain more fibrous astrocytes than other parts of the c. n. s. The data obtained are discussed with regard to the results of recent electrophysiological study of sympathetic preganglionic neurons.

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