CONTRACTILE EFFECTS OF PORCINE GALANIN(1-29)-NH2 ON THE RAT ISOLATED GASTRIC FUNDUS - MEDIATION BY POTASSIUM-IONS

Galanin (3-300 nM) evoked reproducible concentration-dependent contrac tions of rat isolated gastric fundus strips, EC50 of the peptide equal led 16.7 nM (6.2-39.2) and the slope of the concentration-response cur ve was 34.8 (24.0-45.7). The maximal response (E-max) to carbachol (30 nM) was not affected by the absence of the potassium ions in the bath ing solution. On the contrary the E-max to galanin (300 nM) was decrea sed by almost 95% by the use of the potassium-free buffer. Re-exposure of the muscle strips to potassium containing bathing medium reversed the inhibition by about 35%, yet the value remained significantly lowe r than that of the control. Apamin (1 and 2 mu M), glybenclamide (10 m u M), clofilium tosylate (10 mu M) did not significantly influence the E-max to carbachol. Apamin or glybenclamide did not affect the contra ctile action of galanin, while clofilium attenuated the E-max to the p eptide in a concentration-dependent manner, the EC50 of the agent bein g 9.44 mu M (164 nM-541 mu M). It was concluded that the potassium ion s play a modulatory role in gastric smooth muscle contraction followin g galanin receptor stimulation, probably by interacting with the extra cellular calcium influx. (C) 1997 The Italian Pharmacological Society.