Reproductive Medicine, Chronobiology
and Human Ethology, ISSN 0172780X
Vol.24 No.1/2, Feb-Apr 2003
and Familiar Stressors
of the HPA axis after chronic variable stress: Effects of
novel and familiar stressors
L. Simpkiss & Darragh P. Devine
of Florida, Behavioral Neuroscience Program, Department of
Psychology, Gainesville, FL 32611-2250 U.S.A.
August 21, 2002 Accepted: September 13, 2002
stress, novelty, HPA axis, adrenocorticotrophin, corticosterone
We examined the role that novelty plays in determining interactions
between chronic and acute stress, when both the chronic and
acute stressors emphasize emotional processing (i.e. stressful
stimuli that do not present immediate threats to somatic homeostasis,
and are processed primarily by limbic and forebrain circuits).
Rats were exposed to a chronic variable stress (CVS) regimen,
and were subsequently tested to evaluate responses to novel
and familiar acute stressors. One group was exposed to CVS
that included restraint, and was then tested with this familiar
stressor. Another group was exposed to CVS that did not include
restraint, and were tested with restraint as a novel stressor.
Additional rats were not chronically stressed. Plasma adrenocorticotrophic
hormone (ACTH) and corticosterone (CORT) were assayed.
When the rats were exposed to familiar acute stress after
CVS, ACTH responses were blunted. The ACTH responses were
normal in the rats that were tested with novel acute stress
- the responses resembled those of rats that had no prior
stress experience. CORT responses did not differ between the
groups, regardless of stress history.
Despite the fact that all the chronic and acute stressors
emphasized emotional processing of aversive stimuli, and thus
likely involved overlapping limbic and forebrain circuits,
the hormonal responses differed depending upon familiarity
with the acute stressor. Further research is required to identify
the neuronal mechanisms that mediate these differing responses
to novel and familiar emotional stressors.
Copyright © Neuroendocrinology Letters 2003
Society of Integrated Sciences
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