Studies of electrical characteristics of command neurons of the defensive reflex have shown that membrane potential does not reliable differ for both naive and learned snails with changing of the calcium concentrations in external solution. With increasing of the concentrations of calcium ions it is observed the increases of threshold potential from 14 + 0.7 mV in 2.5 mM Ca2+ to 21.8 + 0.9 mV in 20 mM Ca2+ for naive snails. Threshold potential decreases from 16.8 + 0.6 mV (saline solution for snail--10 mM Ca2+) to 13.3 + 0.6 mV in 20 mM Ca2+ with increasing of calcium concentrations for learned snails, and under its reduction it is also decreased, but less remarkably, than for naive, to 11.8 + 0.8 mV in 2.5 mM Ca2+. On the same scheme it is changed a critical level of depolarization: for naive snails it decreases with increasing of the calcium concentrations, and for learned snails it increases either with increasing of the calcium concentrations, and so with its reduction.