Investigation of the effects of α1-adrenoceptor antagonism and L-type calcium channel blockade on ejaculation and vas deferens and seminal vesicle contractility in vitro.

INTRODUCTION

Premature ejaculation is one of the most common male sexual dysfunctions. Current pharmacological treatments involve reduction in penile sensitivity by local anesthetics or increase of ejaculatory threshold by selective serotonin reuptake inhibitors. α1-Adrenoceptors (α1-ARs) and L-type calcium channels are expressed in the smooth muscles of the male reproductive tract, and their activations play an important role in the physiological events involved in the seminal emission phase of ejaculation.

AIM

To evaluate if the inhibition of the contractility of the vas deferens and seminal vesicle by α1-AR antagonism or the L-type calcium channel blockade can delay ejaculation.

METHODS

The effects of the α1-AR antagonist tamsulosin and of the L-type calcium channel blockers, nifedipine and (S)-(+)-niguldipine, on contractions induced by norepinephrine in the rat vas deferens and seminal vesicles in vitro and on the ejaculation latency of male rats in behavioral mating tests were evaluated.

MAIN OUTCOME MEASURE

Tension development of vas deferens and seminal vesicles in response to norepinephrine in vitro and behavioral mating parameters were quantified.

RESULTS

Tension development of vas deferens and seminal vesicle to α1-AR activation was significantly inhibited by tamsulosin, nifedipine, and (S)-(+)-niguldipine. Tamsulosin displayed insurmountable antagonism of contractions induced by norepinephrine in the rat vas deferens and seminal vesicle. Ejaculation latency of male rats was not modified by tamsulosin, nifedipine, or (S)-(+)-niguldipine; however, both the number and weight of the seminal plugs recovered from female rats mated with male rats treated with tamsulosin were significantly reduced.

CONCLUSION

Seminal emission impairment by inhibition of vas deferens or seminal vesicle contractility by L-type calcium channel blockade or α1-AR antagonism is not able to delay the ejaculation.