Effects of synthetic biologically active peptides on giant neurones identified in the left buccal ganglion of an African giant snail (Achatina fulica Férussac).

1. The effects of synthetic biologically active peptides, including Met-enkephalin, substance P, oxytocin, Arg-vasopressin, proctolin and FMRFamide, on the following four buccal neurones were examined: d-LBAN (dorsal-left buccal anterior neurone), d-LBMN (dorsal-left buccal medial neurone), d-LBCN (dorsal-left buccal central neurone) and d-LBPN (dorsal-left buccal posterior neurone). These peptides were examined at 10(-4) M. 2. Oxytocin excited d-LBAN and slightly excited d-LBCN, while this inhibited d-LBMN. Arg-vasopressin excited slightly d-LBAN and d-LBCN, but this had some times no effect. FMRFamide inhibited d-LBAN, and slightly inhibited d-LBCN. 3. No direct synaptic connection from the two ventral cerebral giant neurones, v-LCDN and v-RCDN, to the four buccal giant neurones was found, though the two cerebral neurones innervate the cerebro-buccal connectives.