NITRIC-OXIDE MEDIATES PENILE ERECTION IN CATS

The present study was undertaken to investigate the in vivo effects of nitric oxide (NO) mediating agents injected intracavernosally on peni le erection in cats. All NO donors increased the cavernosal pressure a nd penile length in a dose-dependent manner. The maximal effects on ca vernosal pressure and penile length induced by s-nitrosocysteine (NO-C YS) and s-nitroso-n-acetylpenicillamine (SNAP), respectively, were 8-f old and 5-fold increases in pressure, and 45% and 34% increases in len gth when compared with baseline values. These changes were comparable to that caused by the control drug combination (papaverine, phentolami ne and prostaglandin E1). The effects of acetylcholine (ACh) and subst ance P on cavernosal pressure and penile length were less than those o btained with the control drug combination, NO-CYS (p < 0.01), or SNAP (p < 0.05). N(omega)-nitro-1-arginine-methyl-ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, significantly decreased the effects of NO-CYS, ACh and substance P on penile erection. This in vivo study wi th NO donors and an NOS inhibitor suggests that NO is a mediator of pe nile erection in cats.