Effects of Aging on Alpha1-adrenoceptor Mechanisms in the Isolated Mouse Aortic Preparation

The effects of aging on alpha(1)-adrenoceptor (alpha(1)-AR)-mediated contractile response in endothelium-removed aortic preparations isolated from 5- to 40-week-old (5-, 6-, 8-, 10-, 20-, 40-weeks) mice were studied in the presence of propranolol. The potency of noradrenaline, estimated as its pD(2) value, increased with age from 5- to 10-weeks, but decreased thereafter with age from 10- to 40-weeks. However, the affinity of prazosin (pA(2) value) did not change with aging. These results suggest that age-related change in noradrenaline potency is not attributable to the change of drug affinity to alpha(1)-ARs, but is possibly due to drug affinity-unrelated factors such as change of the reserve of alpha(1)-ARs.