Biomedical subjects
Publications and source records attributed to G M Sharovarova.
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The dependence of the reversal potential (Erev) of intracellular end-plate potentials (epp) on activity patterns was studied in frog neuromuscular preparations. A shift of Erev to the positive side was found with change in frequency of stimulation from 1/sec to 50/sec. This shift corresponds to the increase of potassium concentration in the synaptic cleft to 7.0 mM. The effect of potassium concentration [K+]0 in the bath solution on quantal content (m) of epp was studied. The quantity m increased when [K+]0 was varied within the range 4.7-8.7 mM; m decreased when [K+]0 was greater than 8.7 mM. Such a relationship between m and [K+]0 is accounted for by the combined effect of potassium on transmitter secretion and electrogenic processes in motor nerve terminals. The correlation between the change of m with [K+]0 and initial epp amplitudes was found and was attributed to potassium efflux from post-synaptic region in varying quantity depending on the initial epp amplitudes. A scheme of synaptic self-regulation by means of potassium feedback is suggested.
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Effects of different concentrations of potassium ions on function of motor neural endings were studied in the frog neuromuscular - muscular preparations. Quantitative relations between change of the muscle fibers' membrane rest potential and parameters of spontaneous or evoked release of transmitter, and the potassium ion concentration in the medium, were revealed. A positive specific effect of relatively low (about 8.7 mM) concentrations on the quantum composition of transsynaptic signals, was shown. The data obtained confirm the supposed participation of the potassium ions in reverse transsynaptic regulation of the neuromuscular - motor synapse function.