Actions of Fusinus FMRFamide-related peptides on the identified central neurones of the snail, Helix aspersa.
The actions of Fusinus FMRFamide-related peptides, that is FMRFamide, FLRFamide, GSLFRFamide, SSLFRFamide, the analogue, GSFFRFamide, and the fragments, LFRFamide and RFamide, were examined on the F1, F2 and F5 neurones of Helix aspersa. All Fusinus peptides exhibit an inhibitory effect on F1 and F5 neurone. On F2 neurone, FMRFamide and FLRFamide exhibit an excitatory effect but GSLFRFamide and SSLFRFamide exhibit an inhibition. The fragment, LFRFamide, is 10-times less potent than GSLFRFamide. GSFFRFamide and RFamide are inactive on F1, F2 and F5 neurone. This evidence indicates that the fragment, LFRFamide, is crucial for the biological activity of Fusinus hexapeptides. The inhibition induced by Fusinus hexapeptides had a reversal potential around -75/-80 mV. It was potentiated in K(+)-free saline, partially abolished either in 10 mM TEA or in 10 mM Co2+ saline and completely abolished in 500 microM 4-AP saline. This evidence indicates that there are multiple K+ channels which are activated by Fusinus hexapeptides and that the IA is more susceptible than IK and IKCa to these peptides.
Chen
M L
ML
Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, UK.
Walker
R J
RJ
D000109:Acetylcholine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D019835:FMRFamide; D017952:Ganglia, Invertebrate / Q000187:drug effects; D006372:Helix, Snails; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009479:Neuropeptides / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013329:Structure-Activity Relationship
D009479:Neuropeptides; D018377:Neurotransmitter Agents; D009842:Oligopeptides; D019835:FMRFamide; D012964:Sodium; D000109:Acetylcholine; D011188:Potassium