[Desensitization of cholinoreceptors of the somatic membrane of command neurons of Helix lucorum taurica L].

Desensitization of receptors by the rhythmic application of acetylcholine (AC) was studied in Helix lucorum command neurons PPa2, PPa3, LPa2, LPa3. Application of AC induced in them monophasic depolarization wave. Repetitive AC stimulation with intervals less than 1-2 min induced a decrement of the response which gradually reached plato. Rate and degree of desensitization were constant in every following series and did not depend on preceding periods of depression. Response restoration was unchanged if intervals between series were equal. Stimulation with higher frequencies induced more considerable desensitization. Desensitization was specific to the locus of the membrane, on which AC was applied. Extrastimulation (intracellular stimulation and application of AC) did not lead to restoration of the response. It is supposed that desensitization is a short-term process and results from changes in receptors. The obtained data are explained by means of the Katz-Thesleff model of desensitization. As certain characteristics of synaptic depression and desensitization are similar, a suggestion is put forward that postsynaptic receptors can participate in the processes of synaptic effectiveness decrement during habituation.