CARDIOINHIBITORY PEPTIDES FROM LIMULUS-POLYPHEMUS - MODULATION OF THENEUROGENIC HEART

Four neuropeptides have been isolated and sequenced from acetone extra cts of brains of the horseshoe crab Limulus polyphemus. They belong to a newly discovered peptide family in invertebrates. A possible role o f the four peptides from Limulus as cardioregulatory neurotransmitters has been tested on the isolated Limulus heart. Three of the peptides (DEGHKMLYFamide, GHSLLHFamide, and PDHHMMYFamide) produce dose-depende nt decreases in both amplitude and rate of the heart contractions, whe reas DHGNMLYFamide reduces only the amplitude of the heartbeat. All fo ur peptides differ in threshold, potency and duration of their effects .