ABSTRACT
Modulation of the adrenergic activity and interferring with channels such as potassium channels may affect relaxation and contraction of the corpus cavernosum. Sildenafil is a selective inhibitor of phosphodiesterase 5, proven effective in the treatment of erectile dysfunction. The objective of this study was to test the effect of sildenafil on alpha-receptors modulation and potassium channels. In the present study, it was found that the muscle relaxant effect of sildenafil [1 x 10 [-9] to 1 x 10 [-6] M] on phenylephrineprecontracted rabbit corpus cavernosum strips was not attenuated by NG-nitro-L-arginine [3 x 10 [-5] M]. Cumulative addition of sildenafil [1 x 10 [-9] - 1 x 10 [-6] M] and phentolamine [1 x 10 [-9] to 1 x 10 [-6] M] to the organ bath dose-dependently inhibited electrical field stimulation-induced contraction of rabbit corpus cavernosum and rat anococcygeus muscle with close ED50 values. Sildenafil [1 x 10 [-7] M] also inhibited phenylephrine-induced contraction of rat aortic rings by 39.83 +/- 3.01%. In addition. tetraethylammonium [1 x 10 [-3] M] significantly attenuated the muscle relaxant effect of sildenafil [1 x 10 [-9] - 1 x 10 [-6] M] on phenylephrine-precontracted strips of rabbit corpus cavernosum. sildenafil is capable of producing cavernosal smooth muscle relaxation by an additional mechanism involving alpha-receptors and potassium channel opening