GYY4137 is a novel hydrogen sulfide (H2S) releasing molecule with vasodilator activity. The objectives of this study were to investigate: (1) the pharmacological effect of GYY4137 on the reactivity of the corpus cavernosum (CC) from normal and diabetic rats; (2) the contribution of ATP-sensitive potassium (K-ATP) channels and nitric oxide (NO) pathway; (3) the reactivity to vasoactive agonists following ex vivo incubation of the diabetic rat CC with GYY4137. Longitudinal strips of CC from control and diabetic male Sprague-Dawley (SD) rats (n = 5-6 animals per group) were suspended in organ-baths. Responses to GYY4137, carbachol, or phenylephrine (PE) were determined by measurement of changes in isometric tension. The effects of acute incubation of the CC strips with L-NAME (NO synthase inhibitor) or glibenclamide (K-ATP channel inhibitor) on the relaxant responses to GYY4137 were examined. The effect of ex vivo incubation with GYY4137 (10-5 M) on the responses of CC to carbachol or PE was evaluated. We found that GYY4137 provoked relaxation in the CC strips, which was significantly reduced in the presence of L-NAME or glibenclamide. Ex vivo incubation of diabetic CC with GYY4137 resulted in a significant improvement in the vascular responses to the added agonists. We conclude that GYY4137 is a relaxant agonist in SD rats CC, and the response is mediated, at least in part, by NO and K-ATP channels. Brief incubation of diabetic CC with GYY4137 markedly improved the impaired vascular reactivity, thus raising the question whether chronic in vivo treatment of diabetic animals with GYY4137 would have any protective effect, which is worth further investigation.