FMRFamide effects on spontaneous and induced contractions of the anterior gizzard in Aplysia

Abstract

The effects of FMRFamide (Phe-Met-Arg-Phe-NH₂), YGG-FMRFamide (Tyr-Gly-Gly-Phe-Met-Arg-Phe-NH₂), and Met-enkephalin (Tyr-Gly-Gly-Phe-Met) on the isolated Aplysia anterior gizzard were examined. (i) FMRFamide inhibits spontaneous gut activity. While YGG-FMRFamide also inhibits spontaneous activity it is less potent than FMRFamide. Met-enkephalin does not affect spontaneous gut activity. (ii) FMRFamide inhibits the excitatory response of acetylcholine on both the anterior gizzard of Aplysia and the isolated stomach region of Navanax. (iii) Neither FMRFamide, YGG-FMRFamide, Met-enkephalin, nor acetylcholine stimulated the activity of adenylate cyclase in the Aplysia anterior gizzard.