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In freely mobile rabbits with electrodes preliminarily implanted in the brain structures ketamine (5 mg/kg intravenously or 20 mg/kg intramuscularly) exhibited properties of GABA receptor agonist decreasing the direct excitability of the mesencephalic reticular formation and periaqueductal gray matter and reducing their activating effect on the frontal cortex (FC) and dorsal region of the hippocamp (DH). GABA-mimetics (muscimol, baclofen, aminooxyacetic acid) as well as GABA system antagonists (bicuculline, thiosemicarbazide) attenuated ketamine action at the level of DH and especially FC.

In experiments on 796 white rats the role was studied of various neurotransmitter systems (choline-, adreno-, serotonin-, dopamine-, and GABA-ergic) in regulation of processes of engrams reproduction, determined by tests of conditioned passive- and active-defensive reactions in comparison with changes of spontaneous motor activity and oriented reaction. Correlations are analyzed between the changes of animals behavioural reactions in conditions of pharmacological control of activity of the studied neurotransmitter systems.

The effect of systemic administration of agonists and antagonists of GABA system on excitability and intracentral relationships of the brain structures was found during chronic experiments on rabbits with bipolar electrodes implanted in the region of the frontal cortex, dorsal hippocampus, midbrain reticular formation and central gray matter. The changes of the functional state of the cerebral formations were suggested to be related to a different degree of the involvement of GABA receptors of types A and B.

Simultaneous decrease of Ca2+, Mg2+-ATPase activity occurred in rat hypothalamus and myocardium during experimental neurosis. The decrease of the enzymatic activity was more distinct in hypothalamus than in myocardium. In hypothalamus the decreased enzymatic activity maintained within a week after completion of the excitation of the animals.

It was shown in experiments in rats that the increase in the level of endogenous acetylcholine induced by galanthamine entails a reduction in Na+, K+-ATPase of neocortical, hippocampal and truncus cerebri microsomes, and in the content of lactic acid in the brain structures in question. Blockage of M-cholinoreceptors with metamisyl is accompanied by the decreased activity of Na+, K+-ATPase in the neocortex and by its elevation in the truncus cerebri. At the same time the content of lactic acid in the cortex rises and that in the truncus cerebri diminishes. No substantial changes in both the biochemical indicators were recorded in the hippocamp. Inhibition of the central N-cholinoreceptors with eterofen reduces the glycolysis intensity in the truncus cerebri and hippocamp. Meanwhile Na+, K+-ATPase activity in the brain structures remains unchanged.

The antihypoxic effects of etimizol and other nootropics are analysed on various experimental models of hypoxia and during bicycle ergometric exercise in healthy volunteers. Etimizol was shown to relieve amnesia effectively in the origin of which there is the hypoxic component (hypobaric hypoxia, actinomycin D, mechanical injury of the brain). The advantage of etimizol as compared to other nootropics with similar action (meclofenoxate, piracetam) is its high effectiveness at a single administration.

In tests on dogs, rabbits and rats, it has been established that in acute postoperative period, the time of memorizing of conditioned signals (light, tone and metronome) is reduced, the time of realization of conditioned reactions increases, the excitability and the bloodflow of the midbrain reticular formation and Mg-AtPhase activity of pons Varolii raise. In the hippocampus the excitability and local bloodflow lower and the activity of Ca-Mg-ATPhase is enhanced. In the frontal cortex these processes do not change. Functional interrelations of the brain structures in the acute postoperative period are characterized by the weakening of the activating influence of the reticular formation on the frontal cortex and an increase of its suppressive action on the dorsal hippocampus. It is suggested, that the discovered damages in the higher nervous activity are stipulated by the changes in neurochemical organization of the brain.

Aethimizol - and strychnine-induced improvement of the short-term memory in dogs is attened by a rising level of excitability of the mesencephalic reticular formation, ventral hippocampus and of the frontal region of the neocrotex. And, conversely, with the stimulats producing a facilitating effect on the memory the excitability of the dorsal hippocampus, mamillary bodies and the dorso-medial amygdala becomes less intensive. At the same time, the function of the anterio-ventral thalamus, basolateral amygdala and also of the primary visual and accoustic regions of the neocortex remains unchanged. Aethimizol exerts an inhibitory effect on the lateral and ventro-medial hypothalamus whereas strychnine raises the excitability of the later and does not change the function of the ventro-medial hypothalamus. The lack of stimulating effect of caffeine on the memory is due to a different organization of the brain.

In conditions of stimulation of adrenergic mechanisms with ephedrine, there was an improvement of the memory engrams reproduction (MER). Blockade of the alpha-adrenergic system by pyrroxan more expressively impeded reproduction of a passive defensive habit in comparison with the action of a beta-adrenolytic, the obsidan. Stimulation of MER processes was accompanied by a parallel activation of glucose-6-phosphate- and 6-phosphategluconatedehydrogenases of pentose path in the tissues of the frontal area of the cerebral cortex and pons Varolii. Blockade of alpha-adrenoreceptors suppressed the activity of the given enzymes in the same structures, while the obsidan suppressed the dehydrogenases of the pentose path only in the frontal zone of the neocortex.

On 22 rabbits with bipolar electrodes chronically implanted in the dorsal hippocampus and the mid-brain reticular formation, it has been established that a submaximal physical load in non-trained animals results in a stable drop of excitability of the studied structures. In the process of a 30-day training programme the hippocampus excitability was lowered, while the reticular formation excitability after a short-term lowering increased and returned to the initial level on the 20th day of training. On the EEG of the studied structures, high-amplitude activity predominated, local blood flow increased only in the reticular formation. The nature of functional interrelations of the studied structures changed both in the non-trained animals and during training.

Full recovery of short-term memory (maximum time of delayed reactions) and of the structure of situational conditioned reflex and differentiation inhibition in dogs is observed in 1.5-2.5 h after tranquil-anaesthesia (diazepam-ketamine in doses of 0.3-15 mg/kg correspondingly) and dissociative anaesthesia by ketamine (15 mg/kg) in 6-8 h after neuroleptanalgesia (droperidol-fentanyl 2.5-0.05 mg/kg correspondingly), 20-24 h after narcosis by thiopental sodium (30 mg/kg) and by the end of the 3d day after neuroleptanaesthesia (droperidol-ketamine 2.5-15 mg/kg correspondingly). The recovery of the reaction of memory trace reproduction (of conditioned reaction of passive avoidance in rats) after various types of general anaesthesia is observed mainly in the same sequence, but on the average a day later than the short-term memory in dogs.

It has been established in chronic experiments on rabbits that accumulation of endogenous acetylcholine (galanthamine--1 mg/kg) prevents the development of sodium hydroxybutyrate (500 mg/kg) ability to increase the excitability of the mesencephalic reticular formation and to reduce the level of frontal cortex excitability. Inhibition of the central muscarinic (metamizyl--2 mg/kg) or nicotinic (eterofen--10 mg/kg) cholinoreceptors prevents the stimulant action or sodium hydroxybutyrate on the excitability of the dorsal hippocamp and mesencephalic reticular formation. Blockade of the central N-cholinoreceptors changes the marked effect of sodium hydroxybutyrate on the blood content of the test brain structures. This may attest to the participation of N-cholinoreceptors in the effects of sodium hydroxybutyrate.