Alpha-1d Adrenoceptor Antagonist Inhibits Premicturition Contractions in Rats with Bladder Outlet Obstruction

Aims of Study Lower urinary tract symptoms associated with bladder outlet obstruction include storage and voiding symptoms, and the most bothersome in men with benign prostatic hyperplasia (BPH) is predominantly storage rather than voiding symptoms. Detrusor overactivity, a major cause of irritative symptoms is a common phenomenon in those with BPH. However, the pathophysiology of this detrusor dysfunction remains to be elucidated. Now alpha 1 adrenoceptor (AR1) antagonists are widely used to treat LUTS suggestive of BPH, and this therapeutic agent relieves voiding as well as storage symptoms. The relaxtant effect of AR1 antagonists on the smooth muscle tone in prostatic tissue has been well documented, and this effect is predominantly mediated by AR1a. Because a highly selective AR1a antagonist did not appear to relieve irritative symptoms in patients with BPH despite of a significant increase in urinary flow rate, the role of another distinct subtype of adrenoceptor, especially AR1d adrenoceptor, in the development of storage symptoms has been focused on. Aims of this study was to clarify the effects of a selective AR1d antagonist, naftopidil, on the micturition reflex in rats with bladder outlet obstruction.