Modulation of cholinergic transmission by opiate peptide and FMRFamide on identified neurons of Helix pomatia L. (Gastropoda, Mollusca).

Identified neurons regulating visceral functions in Helix pomatia reacted selectively to FMRFamide peptide applied to the membrane, some becoming depolarized others hyperpolarized. The effect of morphine and leu-enkephalin was similar to that of FMRFamide. The ACh-induced depolarization was decreased by FMRFamide, morphine, leu-enkephalin and naloxone on the neuron LPa5, while this modulatory effect was not observed on other neurons involved in the regulation of visceral functions. The opiate peptides and FMRFamide may play a modulatory role in molluscan CNS.