Galanin inhibits insulin secretion by direct interference with exocytosis

Abstract
Electrically permeabilized RINm5F cells were used to study whether galanin inhibits insulin secretion distally to the generation of soluble second messengers. Ca2+-induced insulin secretion was inhibited by the neuropeptide in a dose-dependent manner. Galanin appears to act via a G-protein as persussis toxin treatment abolished the effect. GTP (100 μM), GDP (100 μM) and a low dose of GTPγS (10 μM) did not affect galanin-mediated inhibition of secretion. In contrast, at 100 μM, GTPγS attenuated and GDPβS abolished the effect of the peptide. We conclude that galanin inhibits exocytosis directly by a mechanism involving a G-protein.