Ischaemia-reperfusion damage induced by torsion/detorsion of the testicles may be a causative factor leading to erectile dysfunction through oxidative stress-dependent changes in the responses of the penile bulb, an erectile tissue of the penis. We aimed at investigating the effects of unilateral testicular torsion/detorsion (2 or 24 hr) treatment on relaxations induced by electrical field stimulation and sodium nitroprusside in rat isolated penile bulb. Male Sprague-Dawley rats used in the study were divided into two groups. The treatment group was subjected to unilateral torsion followed by detorsion for 2 or 24 hr, while the control group underwent only sham operation. For in vitro organ bath experiments, penile bulbs were isolated and responses to relaxant agents and electrical field stimulation (70 V, 1 msec., 0.5-8 Hz, 5 sec.) were recorded on a computer-based data acquisition system via a force displacement transducer. In tissues precontracted with phenylephrine (3 x 10(-6)M), relaxations induced by electrical field stimulation were not significantly different before and after 2 or 24 hr of detorsion. Similarly sodium nitroprusside- (10(-8)-3 x 10(-6)M) and papaverine-induced (10(-7)-10(-4)M) relaxations were also found unchanged in the detorsion group compared to control. In conclusion, spermatic cord torsion did not lead to impairment in nitric oxide-mediated relaxant responses of the rat isolated penile bulb.