[Antihypoxic properties of opiates and substance P]. / Antigipoksicheskie svoistva opiatov i veshchestva P.

Using survival slices of the rat cerebellum, we studied the influence of opiates (alpha- and beta-endorphines, met-enkephalines) as well as substance P (SP) on the impulse activity (IA) of neurons. Low doses of the studied substances (10(-8)-10(-10) M) for the most part increased the IA of the neurons, while high doses (10(6)-10(-5) M) produced biphasic reaction (inhibition-excitation). It is supposed that opiates and SP act as transmitters in the cerebellum. Under increasing hypoxia, opiates and SP manifested antixypoxic properties both in low O22 concentration and under reoxygenation. Opiates and SP proved to be natural antihypoxants involved not only in nociception mechanisms but also in brain adaptation to oxygen deficiency.

Biorhythmologic aspects of seizure activity.

Seasonal and circadian rhythms of neuronal and organism resistance to convulsive effect of strychnine and penicillin were studied in vivo on mice and rats and in vitro on cultured mouse cerebellar sections. Resistance was assessed by the latency of seizures in mice and neuronal response to convulsants in sections. In the night and morning time (0:00-9:00) seizure resistance in mice increased: it manifested in longer latency and lower mortality compared to those in the day and evening time (12:00-21:00). Seizure resistance was minimum in autumn and maximum in winter. Neurons in cerebellar section were most resistant to the convulsive effect of penicillin in autumn and winter and least resistant in spring and summer. Circadian rhythms of cerebellar neuron resistance to convulsants were opposite, which attests to reciprocal relations between epileptogenic and antiepileptic (cerebellar) cerebral structures.

Substance P as a neuromodulator of cerebellar cholinergic systems.

Substance P in low concentrations (10(-7)M) activates rat cerebellar neurons (in slices), while in high concentrations (10(-6)and 10(-5)M) this compound causes a biphasic response (excitation-inhibition). Substance P probably acts as the excitatory neurotransmitter in the cerebellum and produces modulatory effects (triggering and facilitation) on cerebellar cholinergic structures. Substance P reactivates cholinergic excitatory processes, while acetylcholine prevents substance P-induced inhibitory phase. The data suggest that the modulatory effects of substance P are realized via the feedback mechanisms.

[Brain bioenergetic parameters in rats with varying resistance to hypoxia]. / Bioénergeticheskie parametry mozga krys s raznoi rezistentnost'iu k gipoksii.

Spontaneous electrical activity, adenyl nucleotides' and cytochromes' contents, activity of respiratory chain enzymes complex in brain slices, homogenate and isolated mitochondria of rats, preliminary divided into non-resistant (NR) and high resistant (HR) animals by their sensitivity to hypobaric hypoxia have been investigated. It has been shown that in HR animals brain slices high resistant to hypoxia neurons and in NR brain slices non-resistant neurons predominate. ATP content and energetic charge in the HR animals brain slice were maintained at more high level than in NR. The reduction of NAD-depended way of oxidation in low pO2 conditions was greater in brain of NR than in HR animals. Activity of NADH-cytochrome C reductase (rotenon-sensitive) and Km for NADH in HR brain was more higher in the comparison with NR. These data indicate the main role of NADH-oxidase way in the formation of the individual brain resistance to hypoxia.

[Effect of an infralow frequency magnetic field on nerve cell rhythm and their resistance to hypoxia]. / Vliianie infranizkochastotnogo magnitnogo polia na ritmiku nervnykh kletok i ikh ustoichivost' k gipoksii.

The direct effect of infralow-frequency (0.05, 0.1, 0.25 Hz, 100 nT) magnetic fields (MF) was demonstrated on the brain cellular--tissue model--surviving slices of mouse cerebellum. MF influence is a trigger for the nervous cells. MF-5 Hz revealed two-phases response: inhibition and excitation of the impulse activity of neurons. Besides that we recorded convulsive effect of MF. The experiments with simultaneous exposure of hypoxia and MF revealed a prohypoxia effect of MF, when the oxygen concentration was very low and also after reoxygenation. The surviving slices may be used as a model for studying the fine mechanisms of influence of different intensity MF on the nervous cells.

[The correction of energy metabolism disorders in hypoxia by using vitamin K]. / Korrektsiia narushenii énergeticheskogo obmena pri gipoksii s pomoshch'iu vitamina K.

A study was made of the possibility of correcting respiratory chain function disorders in hypoxia by means of the naphthoquinone derivative vitamin K3. The antihypoxic activity of that compound is defined by its donor-acceptor properties and its capability to shunt the electron flow from NADH to CoQ. The effect is more pronounced in the tissues that oxidize mostly the NAD-dependent substrates which is related to rapid inactivation of the given enzymatic complex under hypoxia and correlates with low resistance of the cell using the NADH-oxidase pathway of oxidizing energy substrates to oxygen deficiency.

[The energy mechanism of phasic changes in the spontaneous electrical activity of the neurons during hypoxia]. / Energeticheskii mekhanizm faznykh izmenenii spontannoi élektricheskoi aktivnosti neironov pri gipoksii.

The functional activity of the neurons directly depends on the energy metabolism of the cell, and as the hypoxic effect grows there takes place an interreplaceability of metabolic flows supplying the respiratory chain with energy substrates and reducing equivalents participating in the compensatory maintenance of the energy status of the cell (glycolysis, NAD-dependent oxidation and succinate oxidation in the terminal phase). Due to this, in a vast area of pO2 values there is retained a high degree of impulse activity of neurons characteristic of the specific electrogenic neuron function.

[Effect of pharmacologic preparations on the electrical activity of cerebellar slices under hypoxia]. / Vliianie nekotorykh farmakologicheskikh preparatov na élektricheskuiu aktivnost' srezov mozzhechka v usloviiakh gipoksii.

The effects of some antihypoxants (piracetam, GABA, sodium hydroxybutyrate and gutimine) on the electrical activity of the cerebellar neurons (Purkinje cells) of rats and mice were studied in the surviving slices under normoxia and increasing hypoxia. All the agents were found to produce phase changes in the base-line electrical activity of neurons: alternation of hyperexcitation and inhibition. Under hypoxia GABA and sodium hydroxybutyrate exerted the direct protective action on neuron metabolism supporting its electrogenic function. In the in vitro conditions in contrast to in situ conditions gutimine was shown to behave as a prohypoxant. The possibility of using the brain slices as the test system to study the mechanisms of action of the agents and the prognostic criterion during selection of prohypoxants is discussed.

[Effect of oxygen insufficiency on brain cells in culture and in vitro slices]. / Vliianie kislorodnoi nedostatochnosti na kletki mozga v usloviiakh kul'tivirovaniia i perezhivaiushchikh srezov.

Decrease of the pO2 led to the same phasic changes in the unit activity of Purkinje cells and hippocampal neurons in mice. Purkinje cells proved to be more resistant against oxygen deficiency in tissue culture than in surviving slices. Cells of the optic cortex preserved high level of functional activity at lowering the pO2 to 50%. Still, they were more sensitive to low pO2 as compared with other neurons. Cellular mechanisms responsible for maintenance of neuron functions in oxygen deficiency were found to depend on the energy exchange. Use of tissue culture and surviving brain slices as a mode for studying the cellular adaptive mechanisms, is discussed.

Maturation of cerebellar neuronal elements in a tissue culture.

The process of differentiation of neurons was traced on an organotypic cerebellar culture of newborn mice. Cerebellar cells reach morphological maturity by the 18-21st day of culturing. An increase of the membrane potential begins on the 6-7th day of culturing. It reaches values characteristic for the definitive stage of the neuron (65-75 mV) by the 9-10th day of culturing. Spontaneous action potentials begin to be recorded on the 10-12th day of culturing. At this time they markedly differ in their characteristics from the action potential of the mature neuron. The differences become less noticeable by the 16-18th day of culturing. However, final maturation of the action potential occurs at later times. The formation of specific sensitivity of cerebellar neurons to acetylcholine correlates with the time of formation of the action potential.

[Maturation of neuronal elements of the cerebellum in tissue culture]. / Sozrevanie neironal'nykh élementov mozzhechka v kul'ture tkani.

The morphological and electrophysiological indices of the process of nervous cells differentiation were observed in the organotypical cerebellar culture of the newborn mice. The cerebellar cells reached the morphological maturity in the 18-21 day culture. The membrane potential augmentation began in the 6-7 day culture and reached the magnitude typical for the definitive stage of neuron (65-75 mV), in the 9-10 day culture. Spontaneous APs were recorded only in the 10-12 day culture, their characteristics being sharply different from those of the mature neuron. The difference reduced by the 16-18th day. The final maturity of cerebellar neurons, however as indicated by the AP, occurred still later and correlated with formation of the specific sensitivity of these cells to acetylcholine.

[Effect of semicarbazide on the electrical and metabolic activity of cerebellar and visual cortex neurons in tissue culture]. / Vliianie semikarbazida na élektricheskuiu i metabolicheskuiu aktivnost' neironov zritel'noi kory i mozzhechka v kul'ture tkani.

The influence of semicarbazide (SC), an inhibitor of glutamate decarboxylase (GDC), on electrical and respiratory activity of the Purkinje cells and cortical neurons of mice was investigated in tissue culture. A biphase character of the SC influence on the investigated parameters was demonstrated. The first excitatory phase could be produced by the blocking action of SC on the GDC synthesis. It is suggested that the prevalence of the excitatory background under conditions of blockade of the GABAergic system led to strong depolarization of the nerve cell membrane, evoking the secondary blocking effect under SC influence. The influence of SC was more expressed on the Purkinje cells than on neurons of the visual cortex, which testifies to a higher content of GDC in inhibitory synapses of cerebellar cells and a more active synthesis of GABA there. For both structures a period was discovered (10-14 days of development in tissue culture) when the biphase effect of SC was maximal. The early formation of GABA-inhibitory synapses in the investigated structures of the brain in the ontogenetic development is suggested.

[Morphologic, electrophysiologic and metabolic indices of cerebellar neuron functioning in tissue culture]. / Morfologicheskie, élektrofiziologicheskie i metabolicheskie pokazateli neironov mozzhechka v usloviiakh kul'tury tkani.

A comparative investigation of morphological, electrophisiological and metabolic indices of the functioning of cerebellar neurons developing in vivo and in conditions of the organotypical culture permitted us to distinguish a period (20--25 days) when properties of the culture of nervous tissue most resemble the characteristics of the brain of adult animals. Cultivated nervous tissue may be used as a model for studies of fine mechanisms of the nervous system functioning in the ontogenesis.

[Structural basis of frontal cortex control of thalamic and basal nuclei in dogs]. / Strukturnye osnovy lobno-korkovogo kontrolia talamicheskikh i bazal'nykh iader u sobak.

Fibrillar degeneration after extirpation of the frontal cortical field F2, central part, was observed in dogs by Nauta--Gygax and Fink--Heimer's methods. Degenerated fibrillae were stated to form two bundles and terminate near the neurons of nonspecific thalamic nuclei: n. ret, MD, pf, sprf, as well as in the neurons of specific thalamic nuclei: n. Vna, cgl, cgm, pul. Degenerated processes of the frontal cortex cells projected to the neurons of basal nuclei: the head of nucleus caudatus, putamen, globus pallidus. In the claustrum degenerative changes were not observed.