Effect of Nitric Oxide Donor on Penile Erection in Rats

Jeon, Woo Sung; Park, Tong Choon; Suh, Jun Kyu

Abstract

Nitric oxide (NO) is known to mediate penile erection by activating intracellular cyclic GMP pathway. It is also suggested that cGMP pathway, on penile erection, has dominant role over the other secondary messenger pathway with cAMP, etc. Based on the hyposthesis that activation of NO-cGMP pathway could represent a more physiologic and effective approach in the treatment of erectile dysfunction, several NO donors and activator of cGMP have been used in human and animal studies of impotence. However the efficacy of those remains debatable. In the present study, we investigated the effect of NO donor [linsidomine chlorhydrate (SIN-1), S-nitroso-N-acetylpcnicillamine (SNAP), sodium nitroprusside (SNP)] alone and in combination with zaprinast (cGMP specific phosphodiesterase inhibitor) on penile erection in rats. NO donors used in this study, except SNP, did not induce penile erection sufficiently. SNP-induced penile erection is comparable to the erection induced by cavernosal nerve stimulation. However, direct applicaion of SNP in the treatment of impotence may not be acceptable as it causes a marked hypotension. Zaprinast given intracayernously either alone or in combination with NO donor may not be clinically effective. Combination with zaprinast is not shown to enhance the effect of NO donor on penile erection. Therefore, combination of NO donor with other drugs modulating different pathway may be a therapeutic approach to erectile dysfunction worthy of further investigation.