highlighted topics Physiology of Aging Selected Contribution: Effects of aging on cerebrovascular tone and [Ca2]i

limits of cerebral blood flow autoregulation shift toward high pressures in aged compared with young rats. Intraluminal pressure stimulates contractile mechanisms in cerebral ar-teries that might, in part, cause an age-dependent shift in autoregulation. The present project tested two hypotheses. First, cerebral artery tone is greater in isolated arteries from aged compared with mature adult rats. Second, aging de-creases the modulatory effect of endothelium-derived nitric oxide (NO) and increases vascular smooth muscle Ca2 sen-sitivity. Isolated segments of middle cerebral arteries from male 6-, 12-, 20-, and 24-mo-old Fischer 344 rats were can-nulated and loaded with fura-2. Diameter and Ca2 re-sponses to increasing pressure were measured in HEPES, during NO synthase inhibition [NG-nitro-L-arginine methyl ester (L-NAME)], and after removal of the endothelium. Ce