[Electrophysiological and morphohistochemical study of adrenalectomy on the hippocampal neurons].

Chronic insufficiency of adrenal hormones is a pathology leading to brain dysfunction. In electrophysiological studies, by extracellular recording of spike activity of single hippocampal neurons (HN) caused by high-frequency stimulation of the entorhinal cortex (EC) in rats with unilateral removal of adrenal (adrenalectomy - AE), we analyzed mechanisms of adaptation of neural networks to chronic hormonal deprivation. The balance of excitatory and inhibitory responses, recorded in HN of intact rats was submitted to characteristic changes in dynamics of development of neurodegeneration: the dominating in norm inhibitory responses were decreased at all AE terms (from 42 % to 25 % by the 18th week). On the contrary, the minimal in norm percent of excitatory responses sharply increased (from 17 % to 60 %) at the 25-27th day after AE, which indicates a possible increase of cholinergic neurotransmission. There was recorded a high level of the mean frequency of peristimulus spiking from the 25-27th day to the 18th week after AE, which indicates the high glutamate level or pronounced activation of NMDA receptors. On the whole, the ratio of excitatory/inhibitory HN responses indicates discoordinated activity of neuronal chains of EC-HN under conditions of AE. Histochemical analysis revealed an increased sensitivity to AE in neurons of the CA1 fields. After disturbance of neuronal structure by the 5th day, 25-27 days after AE, there was observed proliferation cell elements in the CA1 field; as a result, by the 10th week, there is observed the complete filling of "devastated" areas of hippocampus and a sharp rise of phosphatase activity in nuclei of dentate gyrus. 18 weeks after AE, the majority of the CA1 field neurons are submitted to chromatolysis, and the phosphatase activity falls. The presented data make certain contribution to understanding of mechanisms of control of cognitive brain functions and plasticity in interconnection with the hormonal factor.

[Protective effect of Vipera raddei venom damage of peripheral nerve]. / Protectivnyi éffekt iada Vipera raddei pri povrezhdenii perifericheskogo nerva.

In rats, single pulse activity of inter- and motoneurons of the spinal cord lumbar segment was studied in stimulation of cut. n. ischiadicus, extensor (n. gastrocnemius) and flexor (n. peroneus communis) after treatment with the Viper raddei venom for 4 weeks. In the control rats, no responses occurred in the n. ischiadicus distal stump, whereas the responses to contralateral nerve stimulation did occur. On the intact side, the responses occurred in opposite sequence. The absence of effects of the cut nerve distal stump stimulation in control rats resulted from the coalescence absence in the proximal stump which suggests atrophy of the distal stump. Morphological data prove a distal stump hypertrophy and restoration of the affected limb motor activity. The findings suggest a possibility of application of the Viper raddei venom for regeneration of injured peripheral nerve.

[The characteristics of the synaptic reorganization in the sensorimotor cortex of cats after the destruction of the symmetrical portion of the cortex in the opposite hemisphere]. / Osobennosti sinapticheskoi reorganizatsii v sensomotornoi kore mozga u koshek posle razrusheniia simmetrichnogo otdela kory protivopolozhnogo polushariia.

Intracellular recording technique has been used to study reactions of corticospinal neurons (CSN) to stimulation of the ipsilateral ventrolateral nucleus (VLN) of the thalamus in acute experiments on adult intact cats and on cats after lesion on the contralateral sensorimotor cortex (exposition from 6 months to 1.5 years). Acceleration of the monosynaptic EPSPs rise phase in slow CSN was revealed in operated animals, which presumed the reorganization of the synaptic contacts in the SD membrane of flow CSN. Detailed analysis of features and branching of CSN axon, collaterals passing to VLN of the thalamus and participating in formation of the ipsilateral pyramidal tract was made by the method of collision test. The significance of the plastic synaptic reconstruction in the ipsilateral thalamo-cortex reverberating system during the outflow formation under conditions of the partial cortex interhemisphere deafferentation is discussed.

[Plastic synaptic reorganization in the sensorimotor cortex of adult cats after destruction of the contralateral nucleus intermedius of the cerebellum]. / Plasticheskaia sinapticheskaia reorganizatsiia v sensomotornoi kore mozga u vzroslykh koshek posle razrusheniia kontralateral'nogo promezhutochnogo iadra mozzhechka.

Using the intracellular microelectrode technique the reactions were investigated in corticospinal neurons (CSN) after stimulation of contralateral (cIP) and ipsilateral interpositus nucleus of cerebellum as well as ventrolateral nucleus of thalamus. Experiments were made on adult intact cats and the same preliminary lesion of cIP nucleus (exposition from 1 to 6 months). Acceleration of the monosynaptic thalamo-cortical EPSPs time to peak in slow CSN was revealed in operated animals. It indicated that there was remote terminal dendrosomatic sprouting and formation of new synapses on proximal segments of SD-membrane of CSN. This made it possible to suppose that there was formed ipsilateral interposito-thalamocortical way which duplicated the same contralateral in intact animals. The contralateral cortico-interposital collaterals in intact and the analogic ipsilateral sprouting in operated animals have been shown.

[Reorganization of the synaptic inputs of the sensorimotor cortex to the red nucleus after the destruction of the cerebellar nucleus interpositus in adult cats]. / Reorganizatsiia sinapticheskikh vkhodov sensomotornoi kory mozga v krasnoe iadro posle razrusheniia promezhutochnogo iadka mozzhechka u vzroslykh koshek.

Responses of the red nucleus to neurons to stimulation of the ipsilateral sensorimotor cortex have been studied in acute cats with preliminary lesion of the contralateral cerebellar nucleus interpositus (exposition from two weeks to a year and longer period) by intracellular recording technique. Acceleration of the monosynaptic EPSPs rise testifying to formation of the terminal dendrosomatic sprouting of axons of the corticorubral neurons on proximal segments of the somatodendritic membrane of the red nucleus neurons was observed. Various division of the sensorimotor cortex were unequally involved in the process of reorganization of synaptic inputs on the level of individual red nucleus neurons.

[Intracellular study of the formation of new synapses and collateral sprouting of red nucleus neurons after destruction of the cerebellar nucleus interpositus in the adult cat]. / Vnutrikletochnoe issledovanie formirovaniia novykh sinapsov i kollateral'nogo sprautinga v neironakh krasnogo iadra posle razrusheniia promezhutochnogo iadra mozzhechka u vzorslykh koshek.

Responses of red nucleus neurons to stimulation of ipsilateral cerebellar nucleus interpositus were studied in cats after lesion of contralateral cerebellar nucleus interpositus within the period ranging from two weeks to one year and seven weeks. Recording of fast and slow mono- and polysynaptic EPSPs showed collateral sprouting of axons of interposito-rubral neurons to occur in various parts of soma-dendritic membrane of rubro-spinal neurons. Stimulation of ipsilateral cerebellar nucleus interpositus evoked antidromic activation in many red nucleus neurons, suggesting the sprouting of axon collaterals from rubro-spinal neurons onto the neurons of ipsilateral cerebellar n. interpositus projecting to the red nucleus.

[Electrophysiologic study of the rubro-nigral projection of the cat]. / Elektrofiziologicheskoe issledovanie rubro-nigral'noi proektsii u koshek.

Peculiarities of short-latency responses evoked in the red nucleus neurons with stimulation of substantia nigra were studied in acute experiments on cats. Analysis of the antidromic activation parameters of these neurons revealed an existence of a rubro-nigral projection. The fact that some rubro-spinal neurons can be antidromically activated from the black substance and n. interpositus of the cerebellum, identifies them as neurons having dichotomized collateral branching of axons. The neurons in question are supposed to maintain a simultaneous positive feed-back with neurons of both the cerebellar n. interpositus and the substantia nigra.

[Synaptic responses of neurons of the red nucleus of the alert cat to stimulation of the sensomotor area of the cortex and the nucleus interpositus of the cerebellum]. / Sinapticheskie reaktsii neironov krasnogo iadra bodrstvuiushchei koshki na stimuliatsiiu sensomotornoi oblasti kory i promezhutochnogo iadra mozzhechka.

Postsynaptic potentials of the red nucleus neurons evoked by stimulation of the cortical sensomotor region and the cerebellar nucleus interpositus were studied in chronic experiments on awake cats by means of intracellules revording. Rubro-spinal neurons identified by their antidromic activation in response to the stimulation. A decrease of the critical depolarization level was a specific feature for mono- and polysynaptic responses of the red nucleus neurons in alert animals. Isolated EPSPs, therefore, were rarely recorded as well as a great number of polysynaptic potentials. Burst discharges of rubro-spinal neurons and intensive activity of the red nucleus interneurons, were observed.

[Synaptic processes in red nucleus neurons in response to stimulation of the entopeduncular nucleus and the globus pallidus of the cat]. / Sinapticheskie protsessy v neironakh krasnogo iadra pri razdrazhenii éntopedunkuliarnogo iadra i blednogo shara u koshki.

Peculiarities of synaptic processes in red nucleus neurons evoked by stimulation of nucleus entopeduncularis and globus pallidus were studied in acute experiments on cats by means of intracellular recording technique. Stimulation of the structures mentioned was found to evoke mono- and polysynaptic excitation of the rubrospinal neurons. Analysis of time parameters of the recorded excitatory postsynaptic potentials suggested activation of axo-somatic and axo-dendritic synapses. Mechanisms of basal ganglia participation in integration of the red nucleus activity are discussed.

[Neuronal mechanisms of red nucleus interaction with brain stem structures]. / Neironnye mekhanizmy vzaimodeistviia krasnogo iadra so strukturami stvola mozga.

Axon collaterals of rubrospinal neurons to various brainstem structures were identified in acute experiments in cats using the technique of intracellular recording of antidromic action potentials in combination with collision testing. A systemic principle of organization of the rubrospinal influences as well as a tendency to synchronous arrival of rubral impulses at various brainstem centres are shown. Most of the brainstem centres are relay nuclei sending direct efferent projections to those cerebellar areas which, in turn, control the red nucleus activity. Besides this loop which provides dynamic cerebellar control of motor activity, the somatosensory information transmission from the dorsal column nuclei of the spinal cord directly to the red nucleus is shown. The recorded mono- and polysynaptic EPSPs evoked by stimulation of the dorsal column nuclei are characterized by peculiarities which suggest that they originate in various parts of the somadendritic membrane of the red nucleus neurons. The mechanisms of integration of the descending motor command by the red nucleus are discussed.

[Distribution and characteristics of the axonal collaterals of the rubrospinal neurons at the brain stem level]. / Raspredelenie i osobennosti kollateralei aksonov rubro-spinal'nykh neironov na urovne stvola mozga.

In acute experiments on cats, intracellular recording of antidromic APs and the collision test, analysis of correlation between the time of antidromic conduction along the axon's main stem before and after collateral branching as well as the time of conduction in collaterals themselves, revealed a tendency to synchronous arrival of rubrospinal impulses to various brain stem centers at the expense of increased conduction velocity in response to lengthened distance between the brain stem structures and the red nucleus. The data obtained is discussed in the light of sensomotor integration mechanisms and role of the red nucleus in planning and actualization of the motor act.

[Synaptic processes in red nucleus neurons induced in the cat by stimulation of the substantia nigra]. / Sinapticheskie protsessy v neironakh krasnogo iadra, vyzvannye razdrazheniem chernoi substantsii, u koshek.

Peculiarities of synaptic processes in red nucleus neurons evoked by stimulation of various parts of substantia nigra and cerebellar interposital nucleus were studied in acute experiments in cats using an intracellular recording technique. Such stimulation is stated to induce mono- and polysynaptic activation of the rubrospinal neurons. Great similarity is found in developing monosynaptic cerebellar and nigral excitatory effects. Convergence of these influences onto the same rubro-spinal neurons is revealed. Functional significance of inputs from substantia nigra to the red nucleus for performance of movements is discussed.

[Classification of the vestibulospinal neurons of the cat Deiter's nucleus]. / Klassifikatsiia vestibulo-spinal'nykh neironov iadra Deitersa koshki

The antidromic activation of neurons in the cat Deiters nucleus to stimulation of spinal cerevical segments was studied using the intracellular microelectrode recording technique. Separate components of the antidromic action potential and its after-deflections were analyzed in fast- and slow-conducting neurons. A direct dependence between the parameters of the after-deflections and duration of the refractory period was revealed for these neurons. Variable responsivity of neurons with the same axonal conductance velocity is shown to be dependent on the after-depolarizing potential.