Age-Related Adaptation of Pituitary-Adrenocortical Responses to Stress

Publisher Website
Google Scholar
Abstract
It has been reported that aged rats show impaired feedback regulatory control of pituitary adrenocorticotropic hormone release by adrenal glucocorticoids, yet, show no age-related deficit in eliciting an adrenocortical stress response when compared to younger animals. However, the effects of age on the capacity of the pituitary-adrenocortical system to adapt from an acute to a chronic stress situation have not been fully resolved. In the present study, groups of 6-month-old (young) and 22-month-old (old) F-344 rats were sacrificed at various times during the 1st (day 1) and 3rd (day 3) acute exposure to a two-way electric shock-escape stress procedure and subsequently during the 28th (day 28) and 56th (day 56) chronic exposure. Determinations of stress-induced corticosterone and adrenocorticotropic hormone responses indicated that: (1) adrenocortical responses were similar between young and old rats on the first stress exposure, whereas by the third stress session corticosterone responses were higher in young than in old rats; (2) attenuation of pituitary-adrenal responses to chronic stress was less in old compared to young rats, and (3) environmental factors may delay the development of age-related physiological alterations in the pituitary-adrenocortical system.