Galanin inhibits glucose-stimulated insulin release by a mechanism involving hyperpolarization and lowering of cytoplasmic free Ca2+ concentration.
The intrapancreatic neuropeptide galanin has been demonstrated to lower plasma insulin levels in vivo. The effects of this peptide on insulin secretion, cytoplasmic free Ca2+ concentration and membrane potential have now been studied in vitro. Glucose-stimulated insulin secretion was inhibited by galanin under these conditions, indicating a direct effect of the peptide on the beta-cells. The neuropeptide reversed both the increase in membrane potential and cytoplasmic free Ca2+ in response to glucose stimulation. At a non-stimulatory concentration of the sugar, galanin induced a slight hyperpolarization without any effect on cytoplasmic free Ca2+. Galanin did not affect K+-induced increase in cytoplasmic free Ca2+, excluding a direct inhibitory effect on the voltage-activated Ca2+ channels. The results indicate that galanin inhibition of glucose-stimulated insulin release involves hyperpolarization with a subsequent decrease in cytoplasmic free Ca2+.
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D003593:Cytoplasm / Q000378:metabolism*; D005260:Female; D019004:Galanin; D005711:Gallopamil / Q000494:pharmacology; D005947:Glucose / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008820:Mice, Obese; D010455:Peptides / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology
D007328:Insulin; D010455:Peptides; C579796:galanin protein, mouse; D005711:Gallopamil; D019004:Galanin; D005947:Glucose; D011188:Potassium; D002118:Calcium