EFFECTS OF LONG-TERM TREATMENT WITH ESTROGEN AND PROGESTERONE ON IN-VITRO MUSCLE RESPONSES OF THE FEMALE RABBIT URINARY-BLADDER AND URETHRATO AUTONOMIC DRUGS AND NERVE-STIMULATION

Ovariectomized virginal rabbits were treated with either estrogen or p rogesterone for 4 to 6 months. In vitro responses of muscle strips of the bladder and circular urethra were examined. Estrogen resulted in b ladder contractions in response to noradrenaline and phenylephrine, wh ereas these agonists were without effect or evoked weak relaxations in castrated animals (and normals). Estrogen also caused a rightward shi ft of the frequency-contraction curve to nerve stimulation. Progestero ne increased bladder sensitivity to contraction-evoking bethanechol. C ontractile urethral responsiveness to bethanechol increased after both steroids. Urethral sensitivity to noradrenaline, evoking contraction, increased following estrogen. Further, estrogen abolished the marked relaxatory urethral response to nerve stimulation of castrated (and no rmal) rabbits and caused contraction only, which was abolished by a co mbination of alpha-adrenoceptor antagonists and scopolamine. When comp aring the present results with those of other studies, it is evident t hat hormone-induced changes become manifest at an early stage. The pre sent animal study gives support for the use of estrogen in the therapy of stress incontinence and, further, it provides no objections to the use of progesterone in combination with estrogen in this condition.