Feline penile erection induced by transurethral administration of sodium nitroprusside

Nitric oxide (NO) is an important mediator in the relaxation of cavernosal smooth muscle. The aim of this study was to investigate the in vivo feline erectile response after transurethral administration of sodium nitroprussid e (SNP), a NO donor drug. Erectile responses after administration of transu rethral SNP were compared with those elicited by an intracavernosal control triple-drug combination (1.65 mg papaverine, 25 mu g phentolamine, and 0.5 mu g prostaglandin E-1). SNP was administered via a 20-gauge Jelco intrave nous catheter in a volume of 200 mu l and changes in intracavernosal pressu re, penile length, and systemic blood pressure were monitored. The control triple-drug combination was administered via a 30-gauge needle at the end o f each experiment to serve as a control reference. Transurethral administra tion of SNP (1-4 mg) induced penile erection in a dose-dependent manner wit h minimal changes in systemic blood pressure. The maximum increase in intra cavernosal pressure and penile length after transurethral administration of SNP (4 mg) was significantly less than after the intracavernosal injection of the control triple-drug combination (P < 0.01). These data suggest that transurethral administration of SNP can induce an erectile response in cat s with minimal side effects.