Effects of galanin on the release of insulin, glucagon and somatostatin from the isolated, perfused dog pancreas

Galanin is a 29 amino acid peptide which has been found in intrapancreatic nerves. The effects of galanin, adrenergic and cholinergic blockade as well as somatostatin on the hormone release from the isolated perfused dog pancreas were studied. It was found that galanin dose-dependently inhibited insulin (P less than 0.001) and somatostatin (P less than 0.001) but not glucagon secretion at normal glucose levels. The lowest galanin concentration that caused a significant suppression of insulin and somatostatin secretion was 10(-11) and 10(-10) mol/l, respectively. Similar effects were evident during stimulation with 2.5 mmol/l arginine. Galanin (10(-9) mol/l) caused a more pronounced inhibition of insulin and somatostatin secretion at high (10 mmol/l) and normal (5 mmol/l) than at low glucose (1.3 mmol/l). In contrast, suppression of the glucagon secretion was only seen at low glucose (1.3 mmol/l). Perfusion of 10(-6) mol/l of atropine, phentolamine and propranolol had no effect on the galanin-mediated (10(-10) mol/l) inhibition of insulin and somatostatin secretion. Galanin (10(-12)-10(-10) mol/l) and somatostatin (10(-12)-10(-10) mol/l) were equipotent in inhibiting insulin secretion whereas only somatostatin exerted a suppression of the glucagon secretion at normal glucose. Thus, galanin exerts a differential effect on islet hormone secretion and may participate in the hormonal control of insulin, glucagon and somatostatin secretion.