Urothelial α1D Receptor is Predominantly Involved in the Adrenergic Facilitation of Micturition Reflex

Abstract

Previous studies using specific antagonists have shown that α1‐adrenergic receptors (AR) in the urinary bladder epithelium (urothelium) serve as a regulator of micturition reflex. To confirm the urothelial adrenergic effect on the micturition reflex, we investigated the functional role of the α1D‐AR subtype in the urothelium on micturition reflex using α1D‐AR knockout (α1D‐KO) mice. An immunohistochemical analysis showed that the α1D‐AR was localized to the umbrella cells in the mouse urothelium. Cystometry using wild‐type mice demonstrated that the intravesical infusion of noradrenaline (NA) into the urinary bladder shortened the intercontraction interval (ICI) in a dose‐dependent manner, without changing the maximum voiding pressure (MVP). In contrast, α1D‐KO mice exhibited no change in the ICI in response to the intravesical infusion of NA. These results indicate a predominant involvement of the α1D‐AR in facilitation of micturition reflex by NA. Interestingly, the intravenous injection of NA did not alter the ICI and the MVP in wild‐type mice. Thus, locally releasing NA might play an important role in the facilitation of micturition reflex via the urothelial α1D−AR subtype.