Expression of muscarinic and nicotinic acetylcholine receptors in the mouse urothelium

Acetylcholine (ACh) and its receptors play a crucial role in bladder physiology. Here, we investigated the presence of muscarinic receptor subtypes (MR) and nicotinic acetylcholine receptor (nAChR) α-subunits in the mouse urothelium by RT–PCR and immunohistochemistry. With RT–PCR, we detected mRNAs coding for all of the five different MR subtypes and for the nicotinic receptor subunits α2, α4, α5, α6, α7, α9 and α10, whereas the α3-subunit was not expressed. Using immunohistochemistry, we localised a panel of acetylcholine receptors in the different layers of the murine bladder urothelium, with predominant appearance in the basal plasma membrane of the basal cell layer and in the apical membrane of the umbrella cells. M2R and subunit α9 were observed exclusively in the umbrella cells, whereas the MR subtypes 3–5 and the nAChR subunits α4, α7 and α10 were also detected in the intermediate and basal cell layers. The subunit α5 was localised only in the basal cell layer. In conclusion, the murine urothelium expresses multiple cholinergic receptors, including several subtypes of both MR and nAChR, which are differentially distributed among the urothelial cell types. Since these receptors have different electrophysiological and pharmacological properties, and therefore are considered to be responsible for different cellular responses to ACh, this differential distribution is expected to confer cell type-specificity of cholinergic regulation in the bladder urothelium.