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Biomedical subjects

S A Saakian

Publications and source records attributed to S A Saakian.

At least 19 recordsLinked to original sources
PubMed1991

[A pharmacological analysis of the GABA-ergic system of the primordial hippocampus in the frog Rana temporaria].

The data on evoked potentials (EP) in the frog primordial hippocampus during the surface application of gamma-aminobutyric acid (GABA), beta-alanine and aminooxyacetic acid in the region of EP recording are presented. These results in the aggregate with the earlier described effects of picrotoxin, bicuculline, muscimol, baclofen (on EP) and GABA (on intracellular potentials) permit to suggest the presence of GABA-ergic inhibitory system and two types of GABA receptors in the frog primordial hippocampus.

Animals↗
PubMed1987

[Effect of piracetam on the habituation of the neuronal cholinoreceptor membrane of the edible snail].

Piracetam is shown to modulate the habituation pattern of cholinoreceptor neuronal membrane in Helix lucorum. Piracetam (10(-2) M) intensified the reversible decrease of depolarization and spike discharge induced by the local microionophoretic rhythmical application of acetylcholine to the neuron soma. The ability of piracetam to intensify the habituation of neuronal cholinoreceptor membrane may serve as a model of its facilitating effect on the development of habituation of behavioural reactions. Piracetam (5.10(-2) M) was shown to induce a shift in the membrane potential towards depolarization in the majority of identified neurons studied.

Acetylcholine↗
PubMed1987

[Study of the conformation of neurospecific cardioactive glycoproteins by optical spectroscopy].

Using selective fluorescence quenching and circular dichroism techniques, the conformation of protein carriers of earlier detected cardiotropic hypothalamic neurohormones was investigated. The experimental results point to essential differences in the structural organization of the above compounds that were designated according to the type of their binding to corresponding hormones as BNH, BNC and BNS. For instance, the circular dichroism spectrum of BNS is typical of proteins that are characterized by a high content of non-ordered structures, a low content of beta-structures and an almost complete absence of alpha-helices. BNC and BNH with nearly the same content of alpha-helical structures are distinguished by the number of "non-ordered glomes" which are more abundant in BNC. These results are in good agreement with the fluorescence quenching data.

Animals↗
PubMed1985

[Characteristics of the electrical activity in hippocampal slices in mice with Corazol kindling].

It has been shown in experiments on hippocampal slices of (CBA X C57BL/6)F1 mice with corazol kindling that the threshold of the appearance of the induced seizure discharge (ISD) in the area CA1 was decreased by stimulation of Schaffer collaterals. Diazepam provoked an increase in seizure susceptibility to corazol and penicillin and reduction of the ISD. The data suggest that alterations in neuronal reactivity, which follow kindling, can be found in an individual hippocampal segment, thus making it possible to investigate this phenomenon at the synaptic and molecular levels.

Animals↗
PubMed1982

[Effect of diazepam on reactivity of hippocampal neurons during blocking of GABA-ergic system].

It was suggested that diazepam action is mediated by the GABA-ergic system. This suggestion was controlled in vitro experiments with hippocampal slices. The GABA-ergic system was blocked by bicuculline and picrotoxin. The influence of diazepam (1 X 10(-6) M) on the population spikes (PS) evoked in the CA1 area by Schaffer's collaterals stimulation manifested itself in a reversible decrease. Bicuculline (1 X 10(-7) M) and picrotoxin (1 X 10(-6) M) induced an increase in the PS amplitude and appearance of additional PS. Diazepam was normally ineffective when applied in conjunction with bicuculline or picrotoxin. The data indicate that the action of diazepam is really mediated by the GABA-ergic system.

Action Potentials↗
PubMed1981

[Mechanism of action of antiepileptic drugs].

The effect of anticonvulsants and tranquilizers on the initiation and spreading of convulsive discharges in rats, as well as on the spontaneous pacemaker activity and the effects of orthodromal stimulation in mollusc neurons are studied. It was found that the anticonvulsants acted mainly on the initiation of the epileptic discharge due to their influence on the mechanisms of endoneuronal rhythms. Diphenin inhibited simultaneously the initiation and the spreading of the convulsive discharge, the spontaneous activity of the neurons, and the responses to orthodromal stimulation. The tranquilizers and suxilep were found to influence only the spreading of the epileptic activity; the tranquilizers did not block the neuronal pacemaker activity and corasol-induced discharges. The authors recommend using the data obtained for choosing antiepileptic combinations in clinical conditions.

Animals↗
PubMed1978

[Specific hypothalamic proteins].

We had previously shown the presence of four protein fractions in hypothalamus of cattle having a coronarodilatatory effect. In this study we have developed methods for the isolation of these proteins and have studied some of their physicochemical properties, amino acid composition, molecular weight, iso-electric point etc. The results obtained have shown that the methods used enable the isolation of quite pure coronaroactive proteins, the content of which in the hypothalamus is equal to 12 mg/kg of fresh tissue. A study of the amino acid composition of these proteins has shown that they are not of the same type. They also differ in molecular weight, in their electrophoretic properties on 7.5% polyacrylamide gel and their iso-electric points. The possibility of a dual function of these proteins as carriers and precursors of corresponding neurohormones is discussed.

Amino Acids↗
PubMed1976

[New findings concerning the coronaroactive proteins of the hypothalamus].

Our previous studies have shown that the two coronarodilatatory hypothalamic proteins isolated by us are not only carriers for neurohormones "K" and "C" but also procursors of coronarodilatory substances. In the present study we have looked at some physico-chemical properties of these proteins through isoelectric focusing and gel electrophoresis as well as the possibility of obtaining coronaroactive fragments by proteolytic enzymes. The results obtained have shown that the isoelectric points of the coronaroactive proteins are between pH 6.2 and 6.4. Polyacrylamide gel-electrophoresis has shown that one of the coronaroactive proteins, the carrier of neurohormone "C", moves towards the anode and is homogenous while carrier of neurohormone "K" is made up of two protein fractions. Under the action of certain enzymes (trypsin and pepsin) two coronaroactive fragments are obtained from the "neutral" protein carrier. Such an effect is not observed following the action of pronase and chymotrypsin. The physico-chemical properties of these fragments require further studies.

Animals↗
PubMedDate not supplied

[Effect of ethanol on excitatory and inhibitory processes in the visual cortex of rabbits undergoing learning].

Subcutaneous ethanol injection to waking rabbits in a dose of 2-6 g/kg causes discoordination of movements, a decline in motor reactions to inhibitory and reinforced light flashes, and appearance of equalizing and paradoxical relations in the number of reactions to these stimuli. Under the influence of ethanol, activating and disinhibitory action of the pain reinforcement on neurones of the visual area temporarily weakens, while the disinhibitory influence of light flashes (CS) is preserved. Judging from the dynamics of phasic reactions to the inhibitory light flashes, the ethanol in a dose of 2-6 g/kg does not influence the inhibitory hyperpolarization processes in the cerebral cortex of rabbits. Tonic inhibition of the cortical unit activity temporarily intensifies after the ethanol injection.

Animals↗
PubMedDate not supplied

[The neurotropic action of kavinton].

The presence of the neurotropic component in cavinton effect was shown as a result of the analysis of the changes in evoked potentials of the frog primordial hippocamp, the surviving slices of the mouse hippocamp and the neuronal activity of the rabbit visual cortex pyramidal neurons at different routes of administration of apovincaminic acid ethyl ether (cavinton).

Animals↗
PubMedDate not supplied

[Effect of ginseng preparations on the activity of identified neurons of Heliz lucorum snails].

It has been demonstrated that the effects of aqueous extracts from the native ginseng and extracts of genseng tissue culture on the activity of identified neurones are identical. Neuronal excitability, tested intracellularly, significantly increases to the 60th minute of drug application, whereas gradually developing depolarization simultaneously disappears. Rhythmic orthodromic stimulation revealed the increase in neuronal responses during ginseng perfusion, the synaptic efficiency remaining constant. It is suggested that changes in transmembrane potential level evoked by administration of ginseng preparations are not related to changes in the excitability. Changes in the adaptive capacities of the neurones in invertebrate animals are due to nonspecific endoneuronal shifts in cellular metabolism induced by ginseng administation.

Animals↗
PubMedDate not supplied

[Specificity of hippocampal field CA3 neuronal responses to repetitive single stimuli].

It has been shown on alert rabbits that responses of field CA3 units to stimuli eliciting (single tones) and not eliciting (single flashes) an activation reaction are substantially different. 75% of units responsive to a flash exhibited: less pronounced tonic extinctive responses, stable structurized phasic reactions and the dynamics of responses in the form of changes in their types. The system of field CA3 units "triggered" by single stimulation is under control of the sensorimotor cortical area. Modulating cortical influences enhance the revealed tendencies of responses of the examined neurones to a single photic stimulus.

Acoustic Stimulation↗
PubMedDate not supplied

[Effect of gamma aminobutyric acid on command neurons of Helix lucorum snail neurons].

Studies have been made of the effect of GABA on the activity of identified neurones of the central nervous system of the snail Helix lucorum. GABA perfusion within first 10 min resulted in the increase of reactions to intracellular and transsynaptic stimulation of the neurones studied, depolarization by 3-4 mV being also observed. After this period, further perfusion decreased the spontaneous activity and neuronal reaction, this effect being accompanied by the decrease in membrane resistance. Synaptic and axonal conduction remained unaffected, although cells responded by the action potentials only to strong stimulation. After 30 min of GABA perfusion, tactile stimulation, which in the intact animals induces the avoidance reaction led to opening of the respiratory orifice, i.e. a component of the respiratory cycle.

Animals↗