The Influence of 17-β-Oestradiol and the Natural Oestrous Cycle on α-Adrenoceptor-mediated Responses of the Cardiovascular System in the Rat

Abstract

Abstract The effect of 17β-oestradiol pretreatment and the natural oestrous cycle on responses of rat cardiac and vascular α-adrenoceptors was investigated. It was found that treatment with the oestrogen had no effect on cardiac adrenoceptor sensitivity, while pretreatment with the hormone caused a significant increase in vascular α2-, but not vascular α1-adrenoceptor responsiveness. Pressor responses of pithed rats to selective oer or α2-adrenoceptor agonists did not alter, however, during the natural oestrous cycle. These findings suggest that changes in oestrogen levels are capable of altering α-adrenoceptor-mediated vascular responses but that the relatively small changes in oestrogen which may occur throughout the natural oestrous cycle do not appear to alter the responses of these vascular α-adrenoceptors.