THE ROLES OF NITRIC-OXIDE IN SEXUAL FUNCTION OF MALE-RATS

Nitric oxide (NO) may mediate penile erection by inhibiting smooth mus cle of the corpora cavernosa, thereby allowing vasodilation of the cor pora. In order to test the role of NO in the sexual function of intact male rats, either the precursor of NO (L-arginine, L-Arg) or an inhib itor of its synthesis ((N)G-nitro-L-arginine methyl ester, NAME) was a dministered systemically before tests of copulation, ex copula genital reflexes, or sexual motivation/motor activity. NAME impaired copulati on in a dose dependent manner. It also decreased the number of ex copu la erections, but it increased the number of ex copula seminal emissio ns and decreased the latency to the first seminal emission. L-Arg marg inally increased the number of penile reflexes, but had no other effec ts. NAME had no effect on sexual motivation or motor activity. The res ults indicate that nitric oxide promotes erection in intact male rats, probably by mediating filling of the corpora cavernosa. The data also suggest that NO inhibits seminal emission, probably by decreasing sym pathetic nervous system activity; this may help prevent premature ejac ulation.