The influence of 17-beta-oestradiol and the natural oestrous cycle on alpha-adrenoceptor-mediated responses of the cardiovascular system in the rat.

Abstract

The effect of 17 beta-oestradiol pretreatment and the natural oestrous cycle on responses of rat cardiac and vascular alpha-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 alpha 2-, but not vascular alpha 1-adrenoceptor responsiveness. Pressor responses of pithed rats to selective alpha 1- or alpha 2-adrenoceptor agonists did not alter, however, during the natural oestrous cycle. These findings suggest that changes in oestrogen levels are capable of altering alpha-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 alpha-adrenoceptors.