The Effect of Hypercholesterolemia on the Contractions of Detrusor Strips in Response to Neural Stimulation in Rats

Abstract

Aim: To investigate the effect of hypercholesterolemia on in vitro contractions of the detrusor smooth muscle stimulated by an electrical field in rats and the relative contributions of cholinergic and noncholinergic neurotransmission. Materials and methods: Sprague-Dawley rats were fed with standard diet (NC group) or with 4% cholesterol diet (HC group). After 4 weeks, the urinary bladder was excised under anesthesia and 4 detrusor strips were prepared. Blood samples were collected for serum lipid profile, and aortic arches were dissected for histopathological examination. In vitro contractile function of the detrusor smooth muscle was evaluated with: 1) electrical field stimulation (EFS) only, 2) EFS in the presence of muscarinic antagonist atropine (10-6 M), and 3) EFS in the presence of atropine and P2X antagonist phosphate-6-azo (benzene-2,4-disulfonic acid) tetrasodium salt hydrate (10-4 M) or P2X agonist alpha,beta-methylene-adenosine-5'-triphosphate (10-5 M). Results: Plasma cholesterol was elevated in the HC group (P < 0.05); there was no sign of atherosclerosis. Although EFS-induced contractions were higher in the HC group, the difference was not significant. Cholinergic or purinergic antagonists decreased contractile response by desensitization with the purinergic agonist. The contribution of cholinergic and purinergic components were also similar in both groups. Conclusion: The contribution of cholinergic and noncholinergic mechanisms of neurotransmission seems to be independent of the high cholesterol content of the diet and the plasma cholesterol level in rat detrusor muscle.