ACTIONS OF GALANIN AND SOME OF ITS ANALOGS ON RAT ISOLATED GASTRIC FUNDUS

The study was undertaken to characterize the effects of porcine galani n (pGal) and some of its analogues on rat gastric fundus muscle strips . pGal, galantide (M15) and pGal(1-14)-[Abu(8)]SCY-I evoked reproducib le concentration-dependent contractions in concentrations of 1-300, 3- 1,000 and 100-3,000 nM, respectively, with EC(50) values of 13, 70 and 187 nM. Hill's coefficient for pGal is 1.03, indicating an interactio n of one pGal molecule with one receptor, fulfilling criteria of class ical receptor theory. For M15 and pGal(1-14)-[Abu(8)]SCY-I. Hill's coe fficients are significantly different from 1, namely 0.73 and 1.56, so that one drug molecule may not interact with one receptor. The stimul atory effects of pGal were not modified by dibenamine 10 mu M or glybe nclamide 1 or 10 mu M. Diltiazem 0.1, 1 and 10 mu M, papaverine 0.1, 1 0 mu M or dibutyryl cAMP (dib cAMP) 100 and 300 mu>M, blocked the cont raction to pGal in a concentration-dependent manner, indicating an imp ortant role for the influx of extracellular calcium ions and regulatio n by cAMP the pGal-evoked contraction. Diltiazem, dibutyryl cAMP and p apaverine were not competitive antagonists of pGal in the stomach smoo th muscle.