ODA, S., FUJIMURA, H., SASAKI, Y, and OHNEDA, A. α₂-Adrenergic Modulation of Glucagon and Insulin Secretions in Sheep. Tohoku J. Exp. Med., 1991, 163 (2), 101-110 - To investigate the effects of α₂-adrenergic receptors on the secretions of pancreatic glucagon and insulin, clonidine, midaglizole and yohimbine were intravenously administered in four conscious sheep. Clonidine infusion at a dosage of 1.0nmol/kg/min produced hyperglucagonemia, hypoinsulinemia and hyperglycemia. Midaglizole or yohimbine was infused for 30min, at doses of 5, 10 and 50nmol/kg/min during the clonidine infusion. The highest yohimbine infusion (50nmol/kg/min) blocked the clonidine-induced responses of glucagon, insulin and glucose. On the other hand, the midaglizole (50nmol/kg/min) infusion brought about no statistical effect on the clonidine-induced responses of glucagon, insulin and glucose. The α₂-adrenergic antagonistic effect of midaglizole was clearly less than that of yohimbine in the present experiments. It is concluded that the glucagon secretion is enhanced and the insulin release is inhibited by α₂-adrenergic stimulation in conscious sheep.