Effects of α1-, α2- and β-adrenoceptor blockers on insulin secretion in the rat

Abstract

Abstract. The effects of α- and β-adrenoceptor blockade on plasma concentrations of insulin and glucose were studied in the anaesthetized rat. Infusion of the α1-adrenoceptor blocker prazocin (80 μg/min), the α2-adrenoceptor blocker yohimbine (15 μg/min) or the non-selective α-adrenoceptor blocker phentolamine (15 μg/min) during 50 min increased plasma insulin levels by about 1.5–2.5 ng/ml. The effects of phentolamine and prazosin on circulating insulin persisted throughout the infusion whereas the effect of yohimbine seemed to be more transient. Plasma glucose levels increased slightly during infusion of prazosin, but tended to decrease in response to phentolamine and yohimbine. The β-adrenoceptor blocker propranolol (15 μg/min) lowered basal plasma insulin and glucose levels. It also depressed plasma insulin during infusion of all three α-adrenoceptor blockers without any appreciable influence on plasma glucose. It is suggested that both α1- and α2-adrenoceptor as well as β-adrenoceptors are involved in the regulation of basal insulin secretion in the rat.