Effect of Ionizing Radiation on the Release of Cholecystokinin in the Hypothalamus of the Rat

This study was designed to identify the mechanisms underlying the reduction in food intake in rats. Measurements were made of the release of cholecystokinin (CCK) stimulated by potassium chloride in the hypothalamus after (a) γ irradiation (60 Co), (b) treatment with the CCK-A and CCK-B antagonists L-364,718 and L-365,260 with and without radiation, (c) bilateral abdominal vagotomy, and (d) vagotomy with and without radiation and with and without L-364,718. The concentrations of CCK in hypothalamus perfusate were measured by a radioimmunoassay. Exposure of rats to 1, 3, 5 and 10 Gy (1 Gy/min) increased release of CCK in the hypothalamus in a manner that was dependent on dose. A dose of 5 Gy was chosen for further studies. Intraperitoneal (i.p.) administration of 10, 20 and 50 μg/kg of L-364,718 did not induce significant changes in release of CCK in sham-irradiated animals. However, the drug decreased the release of CCK induced by radiation in a dose-dependent manner. In contrast to L-364,718, 20-50 μg/kg...