CONTRACTILE EFFECTS OF PORCINE GALANIN(1–29)-NH 2ON THE RAT ISOLATED GASTRIC FUNDUS: MEDIATION BY POTASSIUM IONS

Galanin (3–300 n M) evoked reproducible concentration-dependent contractions of rat isolated gastric fundus strips, EC 50of the peptide equalled 16.7 n M(6.2–39.2) and the slope of the concentration–response curve was 34.8 (24.0–45.7). The maximal response (E max) to carbachol (30 n M) was not affected by the absence of the potassium ions in the bathing solution. On the contrary the E maxto galanin (300 n M) was decreased 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 lower than that of the control. Apamin (1 and 2 μ M), glybenclamide (10 μ M), clofilium tosylate (10 μ M) did not significantly influence the E maxto carbachol. Apamin or glybenclamide did not affect the contractile action of galanin, while clofilium attenuated the E maxto the peptide in a concentration-dependent manner, the EC 50of the agent being 9.44 μ M(164 n M-541 μ M). It was concluded that the potassium ions play a modulatory role in gastric smooth muscle contraction following galanin receptor stimulation, probably by interacting with the extracellular calcium influx.