Induction of Bladder Overactivity by Nerve Growth Factor in Testes in Rats: Possible Neural Crosstalk Between the Testes and Urinary Bladder.

Objectives: To clarify the pathophysiological factor underlying neural crosstalk among pelvic organs, we investigated the possible role of nerve growth factor (NGF) in the neural crosstalk between the testes and urinary bladder.

Methods: Nerve growth factor (10, 30, and 100 µg/mL) or saline was injected into the testes of male Wistar rats. The change in bladder capacity via cystometry and duration of spontaneous scratching behavior induced by NGF in conscious rats was measured. The effects of pretreatment with capsaicin on NGF-induced changes in bladder capacity and behavior were examined. Further, we evaluated the effect of analgesics, indomethacin and morphine, and pretreatment with compound 48/80 on NGF-induced scratching behavior to elucidate the mechanism of the behavior.

Results: Injection of saline into the testes had no effect on bladder capacity or behavior. However, an injection of NGF (30 and 100 µg/mL) reduced bladder capacity, which was regarded as bladder overactivity, and evoked scratching behavior in a dose-dependent manner. Pretreatment with capsaicin inhibited NGF-induced bladder overactivity and scratching behavior. Neither indomethacin nor pretreatment with compound 48/80 affected the scratching behavior, but morphine inhibited the behavior.

Conclusions: The present study provides evidence of a possible new role of NGF in the testes regarding the activation of testicular primary afferent neurons mediated by capsaicin-sensitive C-fibers, which evokes bladder overactivity via neural crosstalk between the testes and the urinary bladder as well as testicular pain.