Aim: To study the effect of diabetes mellitus and insulin treatment on rat penile nitric oxide synthase content. Methods: Male Wistar rats were divided at random into two groups: the Control (n=8) and the Diabetic (n=17). Diabetes mellitus was induced by intraperitoneal injection of streptozotocin. The diabetic animals were then randomly divided into two subgroups: diabetic rats without insulin treatment (n=7) and diabetic rats with insulin treatment (n=10). The neuronal nitric oxide synthase (nNOS) in the penile corpus cavernosum were assayed by immumohistochemical staining with specific antibody to nNOS and the nNOS-positive nerve fibers were counted semiquantitatively under a high power microscope. Results: The nNOS- positive nerve fibres in diabetic rats with treatment was higher than that in diabetic rats without treatment (P<0.05) and lower than that in the controls (P<0.01). The nNOS-positive nerve fibres in diabetic rat without treatment were also lower than that in the controls (P<0.01). Conclusion: In streptozotocin-induced diabetic rats, the nNOS content in the penile corpus cavernosum was significantly decreased. Insulin treatment at the dose level employed partially restores the penile nNOS content in these rats.
    
    

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