Muscarinic and purinergic receptor expression in the urothelium of rats with detrusor overactivity induced by bladder outlet obstruction

OBJECTIVE: To investigate the expression of muscarinic and purinergic receptors in rat urothelium, and changes in their distribution and expression following detrusor overactivity induced by bladder outlet obstruction (BOO). MATERIALS AND METHODS: Thirty Sprague-Dawley rats were divided into control (10) and BOO groups (20). Partial BOO was induced for 3 weeks and the rats assessed by cystometrography. A portion of the bladder was stained using immunofluorescence for M₂ and M₃ muscarinic receptors, and P2X₃ purinergic receptors. The remainder was dissected into bladder urothelium and the smooth muscle layer, and the expression of the receptor proteins analysed by Western blotting. RESULTS: Cystometrography showed a significant decrease in contraction interval and increase in contraction pressure in the BOO group. On immunofluorescence staining, muscarinic and purinergic receptors were localized in both the urothelium and the muscle layer. Immunoreactivity of M₂ and M₃ muscarinic receptors was greater in the urothelium of the BOO group than in the control group; there was a smaller increase in P2X₃ immunoreactivity. On Western blotting, the expression of M₂, M₃ and P2X₃ receptors was increased in the urothelium of the BOO group, and there was increased M ₃ receptor expression in the muscle layer of the BOO group. CONCLUSIONS: There were detectable changes in muscarinic and purinergic receptors with bladder overactivity induced by BOO. Our results suggest that changes in urothelium receptor expression could have a role in mediating the afferent sensory responses in the urinary bladder.