Proerectile Effects of Selective alpha1 Blockers: A Comparative Study with Rat Model

Sim, Jung Min; Park, Kwanjin; Paick, Jae Seung

Abstract

PURPOSE: The purpose of this study was to investigate the pro-erectile potential of various urethral alpha blockers using pharmacological or electrical induction of erection in anesthesized rats.
MATERIALS AND METHODS
To evaluate the influence on centrally mediated erection, intravenous administeration of terazosin, doxazosin(3, 10, 30microgram/kg), and tamsulosin (0.3, 1, 3microgram/kg), followed by submaximal subcutaneous apomorphine(50microgram/kg) administration, mean arterial pressure(MAP) and intracavernosal pressure(ICP) were recorded over 30 minutes in male anesthesized rats. The time to first response, peaks within 30 minutes, maximal ICP, area under the curve, percentage of ICP/MAP were compared. To evaluate the influence on peripherally induced erections, various doses of alpha antagonists and submaximal cavernous nerve stimulation(0.5ms, 2V, 10Hz) were combined. The ICP increase and ICP/MAP percentage were also compared.
RESULTS
Although various dose response relationships were shown, all three alpha blockers enhanced erectile activity triggered by apomorphine. In terms of time to first response and peaks within 30 minutes, the proerectile effects of terazosin was most prominent whereas those of tamsulosin was minimal, requiring larger doses. In combining with cavernous nerve stimulation, doxazosin and tamsulosin showed moderate proerectile activity, but the highest dose of terazosin was required to enhance ICP increase induced by cavernous nerve stimulation. Despite their pressure lowering effects, all tested alpha adrenergic blockers significantly enhanced the ICP/MAP percentage.
CONCLUSIONS
The present finding clearly indicated that alpha 1 selective antagonists can enhance erectile capacity when combined with central or peripheral stimuli for erection.