The Role of Intracellular Calcium in Changing of ElectricalCharacteristics of Premotor Interneurons in Intact Snails and Snails During Various Forms of Plasticity

Abstract

© 2019, Springer Science+Business Media, LLC, part of Springer Nature. It was previously shown that both associative learning and the formation of long-term sensitization led to the increase in excitability of premotor interneurons of the defensive behavior of terrestrial snail Helix lucorum. In the present study, we analyzed the role of intracellular calcium ions in the maintenance of increased excitability in premotor interneurons of terrestrial snail after the formation of a conditioned defensive reflex. It was shown that the increase of the intracellular Ca2+ concentration after adding caffeine to the solution washing the nervous system of the mollusk led to a decrease of the threshold of action potential and to an increase of the critical level of depolarization without a change of the membrane potential of premotor interneurons in both intact and trained snails. The decrease of the intracellular Ca2+ concentration in premotor interneurons by the intracellular injection of (ethylene glycol-bis (2-aminoethylether)-N, N, N, N-tetraacetic acid) (EGTA) resulted in a significant increase of the threshold of generation of the action potential in intact snails. But the values of threshold of generation of the action potential in trained snails after injection of EGTA did not significantly differ from the values of studied parameters before injection. After application of the membrane-penetrating chelator, BAPTA-AM, the changes in the membrane and threshold potentials of premotor interneurons of intact and trained snails were not observed. Our results demonstrated that both the increase and decrease of intracellular Ca2+ concentration were not involved in maintaining the changes of membrane characteristics of premotor interneurons observed after associative learning.