Abstract
A single injection of oCRF at either 2 or 15 ug/kg BW was given to old (19-21 mo) and young (4 mo) male rats, and plasma ACTH and corticosterone (CORT) were measured. Both doses of CRF caused a significant increase in plasma ACTH by 5 min in both age groups (p<0.01), but young rats had significantly greater ACTH levels by 25 min after injection (p<0.05) compared with old. Plasma CORT in both age groups was significantly elevated (p<0.01) above preinjection values by 5 min after either dose of CRF. However at 5, 15, and 25 min, young animals had significantly greater levels of CORT (p<0.05) compared with old. These results indicate that old male rats have a diminished capacity to secrete ACTH in response to oCRF; this decreased sensitivity may be responsible for decreased release of ACTH and CORT observed in old rats in response to stress.
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