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Updated: May 28, 2026
Detrusor Underactivity Model in Rats by Conus Medullaris Transection
Published on: August 28, 2020
Effect of tamsulosin on bladder blood flow and bladder function in a rat model of bladder over distention/emptying
Hiroko Okutsu1, Seiji Matsumoto, Akiyoshi Ohtake
1Applied Pharmacology Research Laboratories, Astellas Pharma, Inc., Tsukuba, Japan.
Purpose:
Decreased bladder blood flow was the subject of a recent study as a pathophysiological cause of bladder overactivity. We developed a rat model of bladder over distention/emptying induced bladder overactivity and investigated the effect of the α(1)-adrenoceptor antagonist tamsulosin on bladder blood flow and bladder function in this model.
Materials And Methods:
The bladder was distended with 2 ml saline using anesthesia for 2 hours (over distention) and then emptied. Bladder blood flow was measured using a perfusion imager. Micturition behavior and parameters were observed using a metabolic cage and a cystometry method, respectively, from 2 hours after bladder emptying. After model establishment was confirmed we examined the participation of afferent C-fibers and the effects of tamsulosin in rats pretreated with capsaicin (Sigma-Aldrich®) (125 mg/kg) and tamsulosin (1 μg/kg per hour), respectively, using a metabolic cage.
Results:
Decreased bladder blood flow was observed upon over distention with partial recovery at emptying. Bladder over distention/emptying increased micturition frequency and decreased mean voided volume in the micturition recording study, and decreased the intercontraction interval and voided volume without affecting micturition pressure, threshold pressure or post-void residual volume in the cystometry study. Capsaicin pretreatment did not affect bladder overactivity. However, 1-week continuous treatment with tamsulosin increased bladder blood flow after bladder emptying, resulting in decreased micturition frequency and increased voided volume.
Conclusions:
Bladder over distention/emptying induced bladder blood flow decrease/partial recovery and caused bladder overactivity via a mechanism other than capsaicin sensitive C-fiber activation. Findings in tamsulosin treated rats confirmed the potency of tamsulosin to increase bladder blood flow and ameliorate bladder overactivity.
