Effects of Glucagon, Neurotensin, and Vasoactive Intestinal Polypeptide on Somatostatin Release from Perifused Rat Hypothalamus*

Abstract

The effects of neuropeptides on the release of immunoreactive somatostatin (SRIF) from the rat hypothalamus were examined in vitro using a perifusion system. Twelve hypothalamic halves of male rats were placed on a Sephadex G- 25 column and continuously eluted with Krebs-Ringer bicarbonate buffer, pH 7.4, at 37 C. A high potassium concentration (56 mM) stimulated SRIF release in a calcium-dependent manner. The infusion of glucagon (10^-7, 5 × 10^-7, and 10^-6 M) resulted in a dose-related increase in the release of SRIF. Neurotensin (10^{- 6} M) also stimulated SRIF release, whereas vasoactive intestinal polypeptide (10^-7 and 10^-6 M) inhibited SRIF release. SRIF release was not affected by cholecystokinin-octapeptide (10^-6 M), cholecystokinin-tetrapeptide (10^-6 M), or TRH ((10^-6 M). These findings suggest that SRIF release from the rat hypothalamus is influenced by glucagon, neurotensin, and vasoactive intes inal polypeptide.