β(3)‐Adrenoceptors in the normal and diseased urinary bladder—What are the open questions?

β(3)‐Adrenoceptor agonists are used in the treatment of overactive bladder syndrome. Although the relaxant response to adrenergic stimulation in human detrusor smooth muscle cells is mediated mainly via β(3)‐adrenoceptors, the plasma concentrations of the therapeutic dose of mirabegron, the only clinically approved β(3)‐adrenoceptor agonist, are considerably lower than the EC(50) for causing direct relaxation of human detrusor, suggesting a mechanism of action other than direct relaxation of detrusor smooth muscle. However, the site and mechanism of action of β(3)‐adrenoceptor agonists in the bladder have not been firmly established. Postulated mechanisms include prejunctional suppression o…