In vivo study on the effects of α 1-adrenoceptor antagonists on intraurethral pressure in the prostatic urethra and intraluminal pressure in the vas deferens in male dogs

• Published in: European journal of pharmacology Vol. 580; no. 1; pp. 256 - 261
• Main Authors: Noguchi, Yukiko, Ohtake, Akiyoshi, Suzuki, Masanori, Sasamata, Masao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2008
• Subjects: Intraluminal pressure of vas deferens; Intraurethral pressure; α 1-adrenoceptor antagonist; Intraurethral pressure; α 1-adrenoceptor antagonist; Intraluminal pressure of vas deferens
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2007.11.003

α-adrenoceptor antagonists are used worldwide for the treatment of voiding dysfunction associated with benign prostatic hyperplasia. Recently, abnormal ejaculation, an adverse effect associated with their use, has attracted attention. Here, we simultaneously investigated the effects of α 1-adrenoceptor antagonists on intraurethral pressure in the prostatic urethra and intraluminal pressure in the vas deferens in anesthetized male dogs, and compared their tissue selectivity. Phenylephrine, an α 1-adrenoceptor agonist, induced simultaneous increases in intraurethral and intraluminal pressure. Alfuzosin, naftopidil, prazosin, silodosin and tamsulosin dose-dependently inhibited both responses. Comparison of ED 50 values in both tissues showed that silodosin had the highest selectivity for the vas deferens (7.5-fold), followed by naftopidil (4.3-fold), alfuzosin (3.8-fold), tamsulosin (2.6-fold) and prazosin (2.5-fold). These results suggest that α 1-adrenoceptor antagonists inhibit contraction of not only the urethra but also the vas deferens in a dose-dependent fashion, and that their high tissue selectivity for the vas deferens over the urethra may contribute to the incidence of abnormal ejaculation.