Fig. 2

α- and β- adrenoceptor Expression and Distribution in the Urinary Tract. Schematic representation of the location and distribution of α and β -adrenoceptors and their subtypes in the bladder, prostate gland and urethra (a), and the kidney and ureter (b). The α-adrenoceptors are divided into α1 and α2 subtypes. The α1 receptors are important receptors in the urinary tract vasculature via their ability to mediate vasoconstriction. Exogenous and endogenous epinephrine and norepinephrine activate these receptors through the Gq family of G proteins, which stimulates the hydrolysis of membrane phospholipids and subsequent generation of inositol phosphate and diacylglycerol (DAG). α and β-adrenoceptors respond to signals from catecholamines (noradrenaline and epinephrine) secreted from the autonomic sympathetic nervous system through the hypogastric and renal nerves to regulate physiological functions and cellular processes. (Insert, color-coding key illustrating the various adrenoceptor subtypes)