Abstract
Tail artery catheters were surgically implanted in Fischer 344 male rats to allow for measurement of mean arterial pressure (MAP, mm Hg) and heart rate (HR, beats/min) in conscious, unrestrained rats. Basal values of MAP and HR were similar for groups of 4, 12 and 24 month old rats. Increments in MAP did not differ among rats of the 3 ages following handling and transfer to a shock chamber or immediately or 5 minutes after exposure to inescapable footshock (2.0 mA, 0.6 sec duration, every 6 sec for 1 min). In contrast, there was a significant age-related attenuation of the tachycardia following handling and transfer of rats to the shock chamber and at the end of footshock. These data are consistent with previous findings of a reduced sensitivity of the aged myocardium to stress-induced sympathetic stimulation.
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