[The effect of the serotonin level on the postsynaptically induced potentiation of neuronal responses in the snail].

The EPSP potentiation induced by the intracellular tetanization of a postsynaptic neuron was studied in the identified neurons of a terrestrial Helix lucorum snail. The high-frequency intracellular tetanization of the command neuron induced a two-phase long-term increase in the amplitude of synaptic responses. The role of 5-HT was studied in potentiation formation. The obtained evidence suggests that the presence of a certain 5-HT concentration in the extracellular fluid is necessary for the second phase formation while the first (short-term) phase is insensible to the 5-HT level in the CNS.