Differences in Responses of Premotor Interneurons to Serotonin and the Precursor of Its Synthesis 5-Hydroxytryptophan in Naive and Sensitized Snails

The responses of premotor interneurons LPa3 and RPa3 of the snail to the application of serotonin and a precursor of its synthesis 5-hydroxytryptophan into a solution washing the preparation of the central nervous system of naive snails and snails after the development of long-term sensitization were studied. The measurements of electrical characteristics demonstrated that during the application of serotonin, a membrane potential of LPa3 and RPa3 interneurons in naive snails significantly decreased by 3.7 mV, while the threshold potential increased insignificantly. The same pattern was also observed during the application of 5-hydroxytryptophan: a significant decrease in the membrane potential by 3.1 mV and an insignificant increase in the threshold for the action potential generation. It was found that the application of serotonin causes a significant decrease in the membrane potential of LPa3 and RPa3 interneurons in sensitized snails by 4.6 mV (depolarization) and an insignificant increase in the threshold potential of premotor interneurons by 0.9 mV. On the contrary, the application of 5-hydroxytryptophan causes an insignificant increase in the membrane potential by 2.5 mV, as well as an insignificant increase in the threshold potential by 0.8 mV.