Effects of intravesical oxybutynin instillation on rat voiding cycle

Oh, Seung Joon; Choo, Myung Soo; Kim, Si Whang

Abstract

A new cystometic procedure that involves a nonstop transvesical infusion of saline followed by repetitive voiding cycles with emission of infused saline in urethane-anesthetized rats was described by Maggi in 1986. We applied this experimental model to assess quantitatively the effects of intravesical oxybutynin instillation on the detrusor activity. Female rats of the Sprague-Dawley were anesthetized with subcutaneous urethane injection (1.0 g/kg) and a double-lumen catheter was inserted through the bladder dome. One channel was connected to a pressure transducer and the other was served for intravesical infusion of fluid, which was connected through an infusion pump to a saline reservoir. The effect of oxybutynin was determined after intravesical administration of oxybutynin (0.001 mg/ml, 0.0025 me/ml, 0.005 mg/ml. 0.01 mg/ml) followed by a twenty-minute retention. After reinfusion of normal saline, urodynamic parameters showed that maximal amplitude of contraction was decreased and both intercontraction interval and cycle period was lengthened in dose-dependent manner, thus leading to suppression of detrusor activity. Our results with oxybutynin demonstrate that this model is suitable for studying graded effects of various drugs on voiding cycle not only for normal micturition reflex but also for various types of neurogenic bladder and these results can be applied as a baseline data for further studies.