Brain angiotensin receptors and sympathoadrenal regulation during insulin-induced hypoglycemia

Simultaneous blockade of systemic AT(1) and AT(2) receptors or converting e nzyme inhibition (CEI) attenuates the hypoglycemia-induced reflex increase of epinephrine (Epi). To examine the role of brain AT(1) and AT(2) receptor s in the reflex regulation of Epi release, we measured catecholamines, hemo dynamics, and renin during insulin-induced hypoglycemia in conscious rats p retreated intracerebroventricularly with losartan, PD-123319, losartan and PD-123319, or vehicle. Epi and norepinephrine (NE) increased 60-and 3-fold, respectively. However, the gain of the reflex increase in plasma Epi (Delt a plasma Epi/Delta plasma glucose) and the overall Epi and NE responses wer e similar in all groups. The ensuing blood pressure response was similar be tween groups, but the corresponding bradycardia was augmented after PD-1233 19 (P< 0.05 vs. vehicle) or combined losartan and PD-123319 (P< 0.01 vs. ve hicle). The findings indicate 1) brain angiotensin receptors are not essent ial for the reflex regulation of Epi release during hypoglycemia and 2) the gain of baroreceptor-mediated bradycardia is increased by blockade of brai n AT(2) receptors in this model.