The effect of age on halothane-induced alterations of contractility in isolated rat aorta

Aging is implicated as a factor which increases the susceptibility to volatile anesthetic-induced depression of the cardiovascular system. However, little is known regarding mechanisms responsible for this enhanced depression. Current experiments examined the effects of 1.2 and 2.4 vol.% halothane on norepinephrine-induced contractility in endothelium-intact and -denuded aortic preparations isolated from 4-, 14-, and 24-month-old Fisher-344 rats. Prior to exposure to halothane, endothelium removal significantly enhanced the sensitivity to norepinephrine in all age groups without altering the maximum tension. Additionally, in endothelium-intact preparations, increasing age from 4 to 24 months decreased the sensitivity to norepinephrine. Exposure to 2.4 vol.% halothane caused a significant decline in the maximum tension generated in response to norepinephrine in all groups. There were no differences in the amount of depression seen with 2.4 vol.% halothane either within age groups or between endothelium-intact and -denuded preparations of the same age. Halothane at 1.2 vol.% caused a significant reduction in the amount of tension generated in the 4-month-old, endothelium-denuded group. However, all age groups with and without endothelium tended to decrease to a similar degree at 1.2 vol.% halothane, and there were no differences either within age groups or between endothelium-intact and -denuded preparations of the same age. In the 4- and 14-month-old endothelium-intact groups, both 1.2 and 2.4 vol.% halothane decreased the sensitivity to norepinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)