Effect of galanin on glucose-, arginine-, or potassium-stimulated insulin release

We have examined the effect of galanin infusion on glucose-stimulated release of insulin from the isolated perfused pancreas of the rat to better characterize the effect of galanin on the first and second phase of insulin. The effects of galanin on insulin release stimulated by L-arginine or high concentrations of potassium were also examined. Whe perfusion of galanin was started 4 min before the start of perfusion of high glucose (16.7 mM), galanin (10^-8-10^-11 M) inhibited both the first and second phase of insulin release in a dose-dependent manner. When perfusion of galanin (10^-8 or 10^-9 M) was started simultaneously with high glucose (16.7 mM), only the second phase of insulin release was suppressed (P < 0.05). Galanin (10^-9 M) failed to inhibit insulin release stimulated by L-arginine (10 and 5 mM) or potassium (25 and 20 mM). These findings suggest that the inhibitory action of galanin on glucose-stimulated insulin release exerted on early intracellular events that occur during the stimulation of insulin release and that are common to both phases. Because galanin does not inhibit insulin release stimulated by L-arginine or potassium, galanin may inhibit glucose-stimulated closure of potassium channels.