Beneficial Effects of Scutellaria baicalensis on Penile Erection in Streptozotocin-Induced Diabetic Rats

We have reported that ethanol extracts of the root from Scutellaria baicalensis Georgi (ESB) relax cavernous smooth muscles via the NO/cGMP system and Ca2+-sensitive K+ channels in the rabbit corpus cavernosum. In the present study, erectile function was assessed by intracavernous pressure (ICP) and mean arterial pressure (MAP) during electrical stimulation of the cavernous nerve. The ICP/MAP ratio was dose-dependently increased by the treatment of ESB in normal SD rats (p < 0.05). To investigate the beneficial effect of ESB on erectile dysfunction in a diabetic animal model, male SD rats were injected with streptozotocin (60 mg/kg) and then 300 mg/kg/day ESB was administered daily for eight weeks. In our in vivo study, administration of ESB in STZ rats significantly increased the ICP, ICP/MAP ratio, area under the curve (AUC), as well as the cavernous cGMP levels. Morphometric analyses showed that ESB administration increased both smooth muscle volume and the regular arrangement of collagen fibers compared to the STZ group. The protein expression levels of endothelial nitric oxide synthase (eNOS) and SM alpha-actin from penile tissues were also significantly increased in the ESB-treated rats. Taken together, these results suggest that ESB ameliorates penile erectile dysfunction via the activation of the NO/cGMP pathways of the penile corpus cavernosum in a streptozotocin-induced diabetic rat model.