Responses of cerebral arterioles to N-methyl-D-aspartate and activation of ATP-sensitive potassium channels in old rats.

The first goal of this study was to examine the hypothesis that aging impairs dilator responses of cerebral arterioles to N-methyl-D-aspartate (NMDA). The second goal was to determine whether aging impairs vasodilatation in response to activation of ATP-sensitive K+ channels. Diameter of cerebral arterioles was measured through a cranial window in anesthetized adult (5 +/- 1 (mean +/- S.E.) months old) and old (26 +/- 1 months old) Fischer 344 rats. In adult rats, NMDA (10 and 100 microM) dilated pial arterioles by 14 +/- 5 and 72 +/- 9%, respectively, from a control diameter of 36 +/- 5 microns. Aprikalim (1 and 10 microM), a direct activator of ATP-sensitive potassium channels, dilated cerebral arterioles in adult rats by 14 +/- 3 and 49 +/- 6%, respectively. Vasodilatation in response to NMDA and aprikalim were similar in old and adult rats. Thus, in contrast to impaired cerebral vasodilator responses to some stimuli, responses of cerebral arterioles to NMDA and activation of ATP-sensitive potassium channels are preserved in old Fischer 344 rats.