Alpha1-adrenoceptors and ejaculatory function.

The abnormal ejaculation of semen is a typical but infrequent side effect of some alpha(1)-adrenoceptor antagonists, particularly those with selectivity for alpha(1A)-adrenoceptors such as silodosin or tamsulosin. Recent clinical studies suggest that this represents a relative anejaculation rather than a retrograde ejaculation. An elegant study in this issue of the journal using alpha(1A) single and alpha(1A/B/D) triple knock-out mice reports a similar phenomenon in rodents. Using a multi-disciplinary approach, the reduced ejaculation and related male infertility is shown to be caused by an impaired function of the vas deferens rather than by alterations in sperm formation, number or function. Similarities and differences between mouse and human data are discussed, particularly why a complete inhibition of all three alpha(1)-adrenoceptor subtypes has the strongest effects in mice whereas apparently only alpha(1A)-adrenoceptor-selective drugs impair ejaculatory function in humans.