Small Cardioactive Peptide B Modulates Limax Feeding Motoneurones

Abstract

ABSTRACT Although first described for its actions on the heart of the snail, Helix (Lloyd, 1978), small cardioactive peptide B (SCPB) has since received attention primarily for its neuronal effects. The effects of SCPB on the feeding neuronal networks of gastropods are particularly well characterized (e.g. Lloyd et al. 1984; Murphy et al. 1985; Sossin et al. 1987; Willows et al. 1988). However, less is known about cellular mechanisms by which the peptide enhances feeding responsiveness. The isolated central nervous system (CNS) preparation of the terrestrial slug Limax maximus is particularly useful for studies which examine the role of peptides in the expression of feeding, since the feeding motor programme can be reliably elicited by chemical stimulation of the lips (Gelperin et al. 1978) or electrical stimulation of the lip nerves (Phifer & Prior, 1985). SCPB increases both the responsiveness of the feeding motor programme and the burst frequency of the fast salivary burster neurone of Limax (Prior et al. 1985; Prior & Watson, 1988). We therefore used intracellular recordings to examine the membrane responses which underlie the ability of SCPB to increase the burst frequency of the fast salivary burster neurone (FSB). Portions of this work have appeared in an earlier abstract (Hess & Prior, 1986).