Abstract
We examined the effect of 17β-estradiol replacement on the blood pressure regulatory response to central and systemic adminsistration of angiotensin II (ANGII) in ovariectmized rats. Seven-week-old female rats were ovariectomized and were assigned into estradiol (E2)- and choresterol (vehicle)-treated groups. Two weeks after the ovariectomy, we measured arterial pressure and heart rate response to icv injection of ANGII (5 ng) and to systemic injection of ANGII (50, 100, and 150 ng/kg) under urethan-chloralose anesthesia. We also examined the blood pressure response to iv injection of phenylephrin (PE). The peak increase in mean arterial pressure (MAP) in response to icv ANGII was not different between E2- and Vehicle-treated rats. MAP returned to preinfusion level within 10 min in E2-treated rats, but MAP remained increased for 30 min in vehicle-treated rats, while heart rate response was similar between two groups. The MAP response to iv ANGII was not affected by E2 replacement, while the decrease in heart rate induced by iv ANGII was significantly attenuated by E2 replacement, suggesting that vasoconstrictor response and baroreflex response controlling heart rate are attenuated by E2 replacement. MAP and heart rate responses to systemic PE was not different between two groups. These results suggest that E2 specifically affects ANGII-associated blood pressure regulation. [J Physiol Sci. 2008;58 Suppl:S182]
