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 ovariec tomized rats pretreated with estradiol (50 mu g/ animal s.c. twice dai ly for five days), untreated ovariectomized rats and intact animals. I n the detrusor muscle, contractions induced by 30 mu M carbachol, when normalized with respect to KCl 100 mM-induced contraction, were simil ar for the three groups. Furthermore, contractions induced by 100 mu M noradrenaline in the isolated urethra were not significatively differ ent between groups. However, the pD(2) value for noradrenaline was gre ater in urethral tissue from ovariectomized rats compared with ovariec tomized -estrogen treated and control rats. A similar result was found for pD(2) values for carbachol-induced contractions on the detrusor m uscle. These results suggest that ovariectomy increases the sensitivit y of the urinary bladder and urethra to the contractile effects of car bachol and noradrenaline, respectively and that this effect is reverse d by in vivo estrogen pretreatment. (C) 1997 Elsevier Science Inc.