[Participation of the adenylate cyclase system in the postsynaptic mechanism of heterosynaptic facilitation].

Changes in the EPSC and Ach-current amplitudes of Planorbis corneus LC-1 and RC-1 neurons has been comparatively investigated after the influence on their adenylate cyclase system in order to reveal postsynaptic mechanisms of the heterosynaptic facilitation. Both responses are n-cholinergic and depend on the membrane conductivity for Na+ and K+. Application of 5-HT has led to an increase of the EPSC and ACh current (in most cases) amplitudes by 100-300%. A negligible increase of the EPSC and at the same time a decrease of the Ach-current were observed in 30% of cells. It was, probably, a result of different contribution made by Na+ and K+ to the activation mechanism of the channel-receptor complex conductivity of the nonsynaptic cell membrane. Effects of 5-HT on EPSCs and Ach-current were imitated by actions of the phosphodiesterase blockers and adenylate cyclase activators. Both the blockers and activators depressed the EPSCs and Ach-current. Thus, activation of the adenylate cyclase system by serotonin has promoted development of the postsynaptic mechanisms of heterosynaptic facilitation in command neurons of Planorbis corneus.