Neurogenic- but not pharmacologic-induced erections are significantly altered by 3 months of experimental diabetes

The goal of the present investigation was to examine the effects of experimental diabetes mellitus (DM) on neurogenic and myogenic mechanisms of erectile function in a rat model. A 3 month period of DM was induced in 2 month old male Fischer 344 rats by either intraperitoneal streptozotocin (STZ) injection (35 mg/kg; n=15), or by subtotal pancreatectomy (n=2), with age-matched control animals (n=13) run in parallel. The effects of DM on erectile function were assessed by monitoring intracavemous pressure (ICP) responses to electrical stimulation of the cavernous nerve and by intracorporal papaverine injection. After 3 months of DM, ICP responses to neurostimulation were significantly attenuated in both STZdiabetic and subtotal pancreatectomy animals, when compared to age-matched control animals; reflexes were also significantly diminished (p<0.05; Student's t test for unpaired samples). Immunostaining with synaptophysin, revealed a significant correlation between decreased neurostimulation and diminished parenchymal and perivascular synaptophysin immunoreactivity in the rat corpora. However, there were no detectable differences in papaverine-induced ICP responses between diabetic and age-matched control animals. These data suggest a differential effect of DM on neurogenic versus myogenic erectile mechanisms, and indicate that this is a promising model system for studying DM-related autonomie neuropathy.