Key Words: α1A adrenoceptor antagonist, Urethral perfusion pressure, Tamsulosin

Objectives: This study was performed to assess the effects of α1A adrenoceptor antagonists on urethral perfusion pressure (UPP) and their therapeutic potential for female bladder outlet obstruction (BOO). Methods: A cannula was inserted into the femoral arteries of female rats to administer tamsulosin (treatment I), doxazosin (treatment II) or phentolamin (treatment III) and to monitor systemic blood pressure. Tamsulosin was also administered to male rats (group IV). UPP and vesical pressures (Pves) were monitored using a triple-lumen catheter. Results: After administration of tamsulosin to group I, frequency decreased significantly, and the duration of minimal urethral relaxation with high-frequency oscillations (Dhfo) was significantly prolonged. With the exception of mean arterial blood pressure (MAP), none of the parameters of group I differed significantly from those of group II and group III. The change to MAP after tamsulosin administration was significantly lower than after doxazosin or phentolamin administration. With the exception of maximal Pves, which was significantly higher in males (group IV) than in females of group I, UPP and Pves curves of male rats were similar to those of females before administration of tamsulosin. The prolonged frequency and Dhfo in group IV after administration of tamsulosin to males was significantly different from that of females. Conclusions: The α1A adrenergic receptor may be a functional subtype in the female rat urethra. α1A adrenoceptor antagonists prolonged Dhfo and decreased the frequency of involuntary bladder contraction. It is possible that administration of α1A adrenoceptor antagonists would not only improve obstructive symptoms, but also ameliorate irritative symptoms by prolonging Dhfo and the frequency of involuntary bladder contractions. (Continence 1: 42-48, 2005) ꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏ