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Biomedical subjects

T A Safonova

Publications and source records attributed to T A Safonova.

At least 19 recordsLinked to original sources
PubMed2005

Neuroeffector connections of giant multimodal neurons in the African snail Achatina fulica.

A new method of making preparations was used to analyse the neuroeffector connections of the paired giant neurons of the African snail Achatina fulica. These neurons were found to induce postsynaptic potentials in the muscles of the mantle, heart, the wall of the pulmonary cavity, and the muscular elements of the renal complex, the pericardium, the sexual apparatus, the walls of the cerebral arteries, the filaments of the columellar muscles, the wall of the abdomen, and the tentacle retractor muscles. Rhythmic neuron activity led to the development of marked facilitation and long-term potentiation of synaptic potentials. The possible significance of the multiple neuroeffector connections of giant neurons is discussed.

Adaptation, Physiological↗
PubMed2004

K+ channels in cardiomyocytes of the pulmonate snail helix.

We used the patch-clamp technique to identify and characterize the electrophysiological, biophysical, and pharmacological properties of K(+) channels in enzymatically dissociated ventricular cells of the land pulmonate snail Helix. The family of outward K(+) currents started to activate at -30 mV and the activation was faster at more depolarized potentials (time constants: at 0 mV 17.4 +/- 1.2 ms vs. 2.5 +/- 0.1 ms at + 60 mV). The current waveforms were similar to those of the A-type family of voltage-dependent K(+) currents encoded by Kv4.2 in mammals. Inactivation of the current was relatively fast, i.e., 50.2 +/- 1.8% of current was inactivated within 250 ms at + 40 mV. The recovery of K(+) channels from inactivation was relatively slow with a mean time constant of 1.7 +/- 0.2 s. Closer examination of steady-state inactivation kinetics revealed that the voltage dependency of inactivation was U-shaped, exhibiting less inactivation at more depolarized membrane potentials. On the basis of this phenomenon, we suggest that a channel encoded by Kv2.1 similar to that in mammals does exist in land pulmonates of the Helix genus. Outward currents were sensitive to 4-aminopyridine and tetraethylammonium chloride. The last compound was most effective, with an IC(50) of 336 +/- 142 micro mol l(-1). Thus, using distinct pharmacological and biophysical tools we identified different types of voltage-gated K(+) channels.

4-Aminopyridine↗
PubMed2004

[Neuroeffector connections of multimodal neurons in the African snail (Achatina fulica)].

Using a new method of animal preparation, the efferent connections of giant paired neurons on the dorsal surface of visceral and right parietal ganglia of snail, Achatina fulica, were examined. It was found that spikes in giant neurons d-VLN and d-RPLN evoke postjunctional potentials in different points of the snail body and viscerae (in the heart, in pericardium, in lung cavity and kidney walls, in mantle and body wall muscles, in tentacle retractors and in cephalic artery). The preliminary analysis of synaptic latency and facilitation suggests a direct connections between giant neurons and investigated efferents.

Animals↗
PubMed1997

[An improvement on the adhesive electrode recording device].

An improved device of the adhesive electrode for recording the bioelectrical potential of animal's syncytial tissue is described in this paper. The main feature of the new device is to place a small chamber between the syringe for building negative pressue and the adhesive electrode. This chamber can keep the electric connection between amplifier and the tissue being recorded, and be placed near the tissue. The negative pressure can be conducted from the syringe by a plastic tube, so the syringe can be placed in any place where it doesn't affect the experiment. By using this new device, good results can be achieved when bioelectrical potential of hearts or gastric muscle of molluscan snails or frogs etc. is recorded. This simple and easy-operating device is practically valuable on studies of the normal functions and pharmacological effects in small animal's syncytial tissues such as heart, and gastric muscle.

Action Potentials↗
PubMed1994

[Heart-stimulating neurons in the subesophageal ganglia of the African snail Achatina fulica Férussac].

5 cardiostimulating neurons belonging to 3 different functional groups were studied in visceral and right parietal ganglia of the African snail. The cell VG-1 formerly believed to be an interneuron, was shown to be a motoneuron of the heart producing the EPSPs in the myocardium. The data obtained show a considerable similarity in organization of the cardioregulating neurons system in different species of the gastropods.

Action Potentials↗
PubMed1990

[The central neurons that inhibit the work of the heart in the edible snail].

The neurones causing the inhibitory postsynaptic potentials (IPSP) with duration 150-200 ms in the myocardium have been identified in the visceral ganglion of Helix pomatia. The neurones are characterized by the high frequency of discharges (2-3 c/s) which changes modulate the heart frequency. IPSP is blocked by d-tubocurarine in the concentration 5.10(-5)-1.10(-4) M.

Animals↗
PubMed1984

[Regulation of snail heart contractions by neurons of the visceral ganglion].

The system of neurons regulating the frequency and strength of heart beats was studied in the snail subesophageal ganglia. Three out of four neurons exerted a short-term phasic effect on the heart. Stimulation of the V6 neuron led to a prolonged increase in the frequency and strength of the heart beats. Activity of two inhibitory cells (about 1-3/sec) was observed whereas excitatory neurons were silent. All the efferent neurons were involved in parallel and did not affect each other.

Animals↗
PubMed1979

Microelectrode investigations of learning phenomena in snail (Helix pomatia) neurones.

We have examined changes of postsynaptic potentials and of pattern activity of the identified silent and oscillatory snail neurones in Helix pomatia during conditioning. Local changes of EPSP or IPSP have been recorded during association following the first stimulus in the silent cells, whereas spike discharges could be observed in response to the 2nd stimulus. In the oscillatory neurones changes of pattern activity have been recorded following the 2nd stimulus, while the first stimulus proved to be ineffective. The formation of temporary connections of snail neurones seemed to be a specific phenomenon, because it was necessary to pair stimuli of different inputs for the development of these modifications. These plastic changes seemed to depend on the interstimulus as well as on the intertrial intervals. Our experimental data underline the probable role of the stimulus parameters and of the electrical properties of neurones during the formation of learned neuronal responses.

Action Potentials↗
PubMed1979

The passive electrical characteristics of giant neurones identified in the central nervous system of Lymnaea stagnalis.

The passive electrical characteristics of four giant neurones in the CNS of Lymnaea stagnalis were studied. The parameters were calculated on the basis of potential transients evoked by hyperpolarizing square impulses. The examined neurones can be classified in two groups, which show significant differences considering the time constant and membrane resistance. This classification is in correlation with the functional properties of the cells. The differences in the passive electrical characteristics of the giant neurones were compared to some data obtained by using voltage clamp method. The role of these parameters in the generation of the single spike and the rhythmic discharge is discussed.

Action Potentials↗