Effects of Intravesical Instillation of Antimuscarinics on Bladder Overactivity Induced by Intravesical Instillation of Adenosine Triphosphate in Rats

Purpose: Adenosine triphosphate (ATP) from the urothelium acts as a sensory neurotransmitter and is augmented in many diseases, such as overactive bladder. We investigated the effects of intravesical instillation of oxybutynin on ATP-induced bladder overactivity to determine whether this effect is mediated by effects on urothelial muscarinic receptors. Materials and Methods: Cystometry (at rate of 0.04 ml/min) was per-formed in female Sprague-Dawley rats (body weight 250 g) under urethane anesthesia (1.2 g/kg). After a 2-hour baseline period, protamine sulfate (10 mg/ml) was instilled for 1 hour, and then ATP (60 mM, pH 6.0) or a mixture of oxybutynin (10−6 M) and ATP (60 mM, pH 6.0) was instilled intravesically. We performed experiments with 4-diphenylacetoxy-N-me-thylpiperidine methobromide (4-DAMP) and methoctramine by the same methods. Cystometric parameters, such as the intercontraction interval (ICI), pressure threshold (PT), and maximal voiding pressure (MVP), were compared