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Caveolae are 50–100 nm large membrane invaginations that represent a plasmalemmal sub‐compartment of relevance for cellular signaling. We aimed to assess whether the muscarinic receptor M3 and the K‐ATP channel Kir6.1 are associated with human detrusor caveolae and to probe the functional relevance of this organization. Muscle strips were dissected from human detrusors and used in ultrastructural, biochemical and mechanical studies. Caveolae were ablated by cholesterol desorption with methyl‐β‐cyclodextrin. The subcellular distribution of M3 muscarinic receptors and Kir6.1 was examined using sucrose density fractionation and immunoelectron microscopy. Desorption of cholesterol right‐shifted the concentration‐response curve for the muscarinic receptor agonist carbachol. Using a K‐ATP channel inhibitor (glibenclamide) and activator (levcromakalim), we were able to inhibit and mimic this effect, respectively. Sucrose density fractionation revealed co‐fractionation of detrusor M3 receptors and Kir6.1, in partial overlap with caveolin‐1. Immunoelectron microscopy showed M3 in caveolae and in sub‐plasmalemmal caveolae‐like structures. Thus, M3 receptors are enriched with Kir6.1 in caveolae, and this organization underpins cholinergic detrusor activation in man.Funded by Swedish Research Council (K2009‐65X‐4955‐01‐3), ALF, Crafoord Foundation.

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