ACTION OF FMRFAMIDE-LIKE PEPTIDES ON PORCINE GASTROINTESTINAL MOTILITY IN-VITRO

Mechanical activity was recorded in circular and longitudinal smooth m uscle preparations isolated from extensive regions of the porcine gast rointestinal tract in response to the FMRFamide-like neuropeptides F8F amide and A18Famide. In all preparations, the peptides were about equi potent in producing phasic contractions or enhancing spontaneous activ ity. The most prominent responses were observed in jejunal longitudina l strips which were on the average 91% (+/-4% SEM, n = 15; 10(-6) M) o f the histamine (10(-5) M) responses. The peptide-induced phasic activ ity was completely abolished by nifedipine but was unaffected by tetro dotoxin, atropine, phentolamine, yohimbine, phenoxybenzamine, proprano lol, methysergide, cimetidine, indomethacin, levallorphane or naloxone . Both peptides enhanced acetylcholine-induced contractions. However, bovine ileum and guinea-pig taenia coli was nor affected by these pept ides. The results indicate that F8F- and A18F-amide contract porcine g astrointestinal smooth muscle by acting directly via non-opioid recept ors on L-type calcium channels. In addition an increase of the sensiti vity to cholinergic stimulation occurs. (C) 1997 Elsevier Science Inc.