Potentiation of glucocorticoid release does not modify the long-term effects of a single exposure to immobilization stress.
BACKGROUND
Previous work has shown that a single exposure of rats to a severe stressor (immobilization, IMO) results, days to weeks later, in a reduced response (desensitization) of the hypothalamic-pituitary-adrenal (HPA) axis to a second exposure to the same stressor.


OBJECTIVE
In the present work, we studied the influence of both length of exposure to IMO and circulating levels of corticosterone on the first day on the degree of desensitization of two sets of physiological variables: HPA hormones and food intake.


METHODS
Rats were given SC saline or ACTH administration and then exposed to IMO for 0, 1 or 20 min. Seven days later, all rats were exposed to 20 min IMO. HPA response was followed on both experimental days by repeated blood sampling and food intake was measured on a 24-h basis.


RESULTS
Both ACTH administration and IMO activates the HPA axis and IMO reduced food intake for several days. A single previous experience with IMO enhanced the post-IMO return of HPA hormones to basal levels on day 8 and reduced the degree of anorexia. The protective effect of previous IMO on food intake was independent of, whereas that on HPA activation was positively related to, the length of exposure on day 1. Concomitant ACTH administration on day 1 did not modify the observed effects.


CONCLUSIONS
Long-term protective effects of a single exposure to IMO are observed even with a brief exposure, but they are not potentiated by increasing corticosterone levels during the first exposure.
Dal-Zotto
Silvina
S
Departament de Biologia Cellular, Fisiologia i Inmunologia, Unitat de Fisiologia Animal, Facultat de Ciències, Institut de Neurociències, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
Martí
Octavi
O
Delgado
Raúl
R
Armario
Antonio
A
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism; D000818:Animals; D003345:Corticosterone / Q000097:blood / Q000378:metabolism; D004435:Eating / Q000502:physiology; D005938:Glucocorticoids / Q000097:blood* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000097:blood*; D013995:Time
D005938:Glucocorticoids; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone