INFLUENCE OF AGE ON NOREPINEPHRINE-INDUCED VASCULAR CONTRACTIONS AS A FUNCTION OF EXTRACELLULAR CALCIUM

  • 1 January 1979
    • journal article
    • research article
    • Vol. 26  (3) , 433-446
Abstract
Age produces various morphological and biochemical changes within the vasculature and changes in the responsiveness of the vasculature to various drugs. The influences of age and extracellular Ca on norepinephrine-induced aortic contractions in male rats were studied. The aging process caused a decrease in sensitivity and responsiveness of rat aorta to norepinephrine-induced contractions. The progressive decrease in maximum contractile force (mg force/mg tissue) in response to norepinephrine due to aging occurred in all the different extracellular Ca concentrations used. The EC50 [median effective concentration] for norepinephrine in aorta from younger animals was directly related to the extracellular Ca concentration. As the animals became progressively older (49-63 wk) the aortic tissues became less sensitive and the calculated EC50 for norepinephrine was not altred by changes in the altered extracellular Ca concentration.