Effect of age on rat aortic responses to acetylcholine and nitric oxide donor (NOC-18)

The purpose of the present study was to examine the effects of age on vascular responses to acetylcholine (ACh) and NO-releasing compound (NOC-18). The studies were performed in young (4 months old, n = 8) and old (22 months old, n = 6) male rats. Responses to ACh and NOC-18 were examined in vitro by using isolated abdominal aortic rings. The maximum relaxation response to ACh, an endothelium-dependent vasodilation, was lower in aortas from old rats. Sensitivity (mean effective concentration; EC50) of ACh in old rats was significantly less than in young rats. There were no differences in maximum NOC-18-induced relaxation, an endothelium-independent vasodilation, in aortas from young and old rats. On the other hand, the concentration-response curve for NOC-18 was shifted to the right and the sensitivity (EC50 to NOC-18) was lower in old rats. These results indicated that both endothelium-dependent vasodilation induced by ACh and endothelium-independent vasodilation induced by NOC-18 are impaired in aorta from old rats.