EFFECT OF DIABETES-MELLITUS ON RESPONSES OF THE RAT BASILAR ARTERY TOACTIVATION OF BETA-ADRENERGIC RECEPTORS

The goal of this study was to determine whether diabetes mellitus alte rs reactivity of the basilar artery in vivo to activation of beta-adre nergic receptors. We measured diameter of the basilar artery in non-di abetic and diabetic (streptozotocin 50-60 mg/kg i.p.) rats during supe rfusion with isoproterenol and norepinephrine, which dilate cerebral b lood vessels via activation of beta-adrenergic receptors. Dilatation o f the basilar artery in response to isoproterenol and norepinephrine w as significantly less in diabetic compared to non-diabetic rats. To de termine whether impaired dilatation of the basilar artery in diabetic rats in response to isoproterenol and norepinephrine was related to an alteration in catalytic activity of adenylate cyclase, we examined di latation of the basilar artery in response to forskolin, a direct acti vator of adenylate cyclase. In contrast to that observed for isoproter enol and norepinephrine, forskolin produced similar dilatation of the basilar artery in non-diabetic and diabetic rats. Thus, the findings o f the present study suggest that diabetes mellitus impairs dilatation of the basilar artery in vivo in response to activation of beta-adrene rgic receptors. In addition, impairment of beta-adrenergic mediated di latation of the basilar artery during diabetes mellitus does not appea r to be related to an alteration in catalytic activity of adenylate cy clase.