In vivo and in vitro investigation of the effects of sildenafil on rat cavernous smooth muscle

Purpose: We investigated the effect of sildenafil on rat erectile tissues i n vivo and in vitro. Materials and Methods: Intracavernous pressure was recorded in pentobarbita l anesthetized, male Sprague-Dawley rats and we studied the effect of 100 o r 200 mug./kg.(-1) sildenafil given intravenously. In an isolated endotheli n-1 contracted strip preparation of rat corpus cavernosum we also assessed the effect of sildenafil on the response to electrical Geld stimulation of the nerves. Results: Electrical stimulation of the cavernous nerve induced a frequency dependent increase in intracavernous pressure of a mean plus or minus stand ard error of mean 55 +/- 3 mm. Hg at 20 Hz., corresponding to a mean of 47% +/- 2% of mean arterial pressure. The 100 mug./kg.(-1) dose did not increa se intracavernous pressure but significantly increased mean decay time of t he pressure response from 16 +/- 3 to 35 +/- 3 seconds (p <0.001). In vitro sildenafil significantly enhanced the amplitude and duration of the relaxa tion induced by the electrical stimulation of corpus cavernosum strips in a concentration dependent fashion. Conclusions: In anesthestized rats sildenafil significantly prolonged the d ecay period of the intracavernous pressure response induced by electrical s timulation of the cavernous nerve but it did not increase the amplitude. Si ldenafil enhanced the amplitude and duration of the relaxant response to el ectrical field stimulation in isolated corpus cavernosum tissue.