7-NITROINDAZOLE - A SELECTIVE INHIBITOR OF PENILE ERECTION - AN IN-VIVO STUDY IN A RAT ANIMAL-MODEL

Objectives. The neuronal isoform of nitric oxide synthase (nNOS) has b een localized in neurons innervating the penis and is believed to be a n important mediator of erection. Using the selective inhibitor 7-nitr oindazole (7-NI), we evaluated the possible role of nNOS in penile ere ction using a rat animal model. Methods. Eighteen Sprague-Dawley rats were divided into three study groups. A sham group (n = 6) received th e vehicle arachis oil, a low-dose group received 5 mg/kg (n = 6), and a high-dose group received 50 mg/kg (n = 6) of 7-NI prior to measureme nt of blood pressure and cavernous nerve stimulation-induced rise in i ntracavernous pressure. Results. A dose-dependent inhibition of erecti on by 7-NI was seen. Control animals had an intracavernous pressure ri se of 55.5 +/- 4.0 cm H2O, whereas the low-dose group had 26.5 +/- 2.8 cm H2O and the high-dose group had 6.2 +/- 2.1 cm H2O. A partial reco very of erection was seen in the low- and high-dose groups after 3 hou rs. Blood pressure was unaffected by 7-NI administration. Conclusions. 7-NI induced a reversible, dose-dependent inhibition of erection with out affecting blood pressure. This in vivo study provides further evid ence of the role played by nNOS in erection.