Alpha1A-adrenoceptor antagonist improves underactive bladder associated with diabetic cystopathy via bladder blood flow in rats

BACKGROUND Patients with diabetes experience lower urinary tract symptoms. Cystopathy may evolve into underactive bladder (UAB), depending on the degree and duration of the symptoms. In the present study, we aimed to investigate the effects of silodosin, an alpha1A-adrenoceptor (AR) antagonist, on UAB in a rat model of diabetes mellitus (DM). METHODS Female Sprague-Dawley rats (6 weeks old) were administered streptozotocin (STZ) (50 mg/kg, i.v.) to establish a DM model. One week after STZ administration, vehicle or silodosin (0.3 or 1 mg/kg/day) was delivered subcutaneously through an osmotic pump. Nine weeks after STZ administration (8 weeks after drug treatment), a catheter was implanted into the bladder under urethane anesthesia. After the measurement of emptied bladder blood flow (BBF), saline was continuously infused into the bladder and intravesical pressure and micturition volume were measured. In another experiment, the bladder was isolated and nerve markers were quantified. RESULTS A cystometrogram showed that bladder capacity (BC), residual volume (RV), and bladder extension (BC/bladder weight) increased by 7.43, 10.47, and 3.59 times, respectively, in vehicle rats in comparison with normal rats. These findings suggested the occurrence of UAB-like symptoms in this model. Silodosin (1 mg/kg/day) inhibited the increase in BC and RV by 49.0% and 46.8%, respectively, and caused a decrease in BBF of approximately 25.5% (when the difference between normal and vehicle was set as 100%) in STZ rats. The nerve marker expression levels tended to be decreased in the bladders of STZ rats and these effects were ameliorated by silodosin. CONCLUSIONS The STZ rats showed increased bladder extension and RV, symptoms that were suggestive of UAB, and these symptoms were ameliorated by silodosin. These results suggested that the alpha1A-AR antagonist would be useful for the prevention or treatment of UAB.