The effect of ovariectomy on the contractile response of the rat isolated detrusor muscle and urethra

Contractile responses induced by carbachol on the detrusor muscle and by noradrenaline on the isolated urethra were compared between ovariectomized rats pretreated with estradiol (50 mu g/ animal s.c. twice daily for five days), untreated ovariectomized rats and intact animals. In the detrusor muscle, contractions induced by 30 mu M carbachol, when normalized with respect to KCl 100 mM-induced contraction, were similar for the three groups. Furthermore, contractions induced by 100 mu M noradrenaline in the isolated urethra were not significatively different between groups. However, the pD(2) value for noradrenaline was greater in urethral tissue from ovariectomized rats compared with ovariectomized -estrogen treated and control rats. A similar result was found for pD(2) values for carbachol-induced contractions on the detrusor muscle. These results suggest that ovariectomy increases the sensitivity of the urinary bladder and urethra to the contractile effects of carbachol and noradrenaline, respectively and that this effect is reversed by in vivo estrogen pretreatment. (C) 1997 Elsevier Science Inc.