[Autoradiographic localization of muscarinic receptors in diabetic rat bladder].

PURPOSE We evaluated the alterations of density, localization and subtype specificity of muscarinic receptors in experimentally-induced diabetic rat bladder. METHODS Five groups of rats were maintained for sixteen weeks 1) diabetic, 2) diabetic insulin-treated (insulin started 8 weeks after the onset of diabetes), 3) sucrose-fed diuretic, 4) sucrose-removed and 5) age matched controls. We used radioligand binding technique and light microscopic autoradiography to define the density and distribution of muscarinic receptors in the rat urinary bladder. RESULTS & CONCLUSION Saturation experiments showed an increase in the density of muscarinic receptors in the bladders of diabetic and diuretic rats compared with age matched controls. Insulin treatment partially reversed the up-regulatin of muscarinic receptors in rat urinary bladder. Autoradiographic studies also indicated that muscarinic receptors were located in all layers of the bladder muscularis. The muscularis of the bladder dome contained higher densities of muscarinic receptors than that of the bladder base. Lack of [3H]QNB binding to transitional epithelium, lamina propria, and tunica adventitia suggests an absence of muscarinic receptors in these regions. Inhibition of [3H]QNB binding to the bladder sections by selective muscarinic antagonists indicated existence of the M2 and M3 receptor subtypes in the muscularis of the rat bladder.