title: Actions of a small cardioactive peptide from Mytilus, APNFLAYPRLamide, on central neurones of Helix aspersa.
abstract: 1. Mytilus small cardioactive peptide (SCP) was originally isolated from the anterior byssus retractor muscle of Mytilus edulis, with a primary structure, APNFLAYPRLamide. The mechanisms of action of this peptide were examined on identified central neurones of the snail, Helix aspersa, using intracellular recordings and a two electrode voltage clamp. 2. 50 microM APNFLAYPRLamide could elicit a long term excitation on F2 neurones, in normal saline, Na(+)-free saline, Ca(2+)-free saline or in 10 mM Co2+ saline. This indicates that the excitatory effect of APNFLAYPRLamide involved an increase in membrane conductance to both Na+ and Ca2+. 3. 10 microM APNFLAYPRLamide potentiated the Ca2+ inward current of F2 neurones while reversibly reducing the ACh-induced membrane current of these neurones. Forskolin had identical effects to those of APNFLAYPRLamide. This indicates that the action of APNFLAYPRLamide may be through a second messenger. In contrast APNFLAYPRLamide potentiated a cholinergic EPSP evoked in F2 neurones. 4. YPRLamide was inactive even at higher concentrations, for example, 100 microM, while LAYPRLamide exhibited activity but with a lower potency. This indicates that LAYPRLamide is the minimum structure required for activating this class of SCP-like peptide receptor. However, the mode of action of APNFLAYPRLamide on the Na+ current of F2 neurones requires further investigation.
authors.affiliation: Department of Physiology and Pharmacology, University of Southampton, U.K.
authors.forename: M L
authors.initials: ML
authors.lastname: Chen
authors.forename: Y
authors.initials: Y
authors.lastname: Muneoka
authors.forename: R J
authors.initials: RJ
authors.lastname: Walker
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D049872:Bivalvia / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D006372:Helix, Snails / Q000187:drug effects* / Q000502:physiology; D007447:Invertebrate Hormones / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: D015220:Calcium Channels; D007447:Invertebrate Hormones; D009842:Oligopeptides; C083036:Mytilus SCP; D005576:Colforsin; D000109:Acetylcholine; D002118:Calcium