Chronic stress produces enduring decreases in novel stress-evoked c-fos mRNA expression in discrete brain regions of the rat

Stress. 2009 Nov;12(6):469-77. doi: 10.3109/10253890802641966.

Abstract

Chronic stress produces numerous adaptations within the hypothalamic-pituitary-adrenal (HPA) axis that persist well after cessation of chronic stress. We previously demonstrated profound attenuation of HPA axis responses to novel environment 4-7 days following chronic stress. The present study tests the hypothesis that this HPA axis hyporesponsivity is associated with reductions in stress-evoked c-fos mRNA expression, a marker of neuronal activation, in discrete brain regions. Adult male Sprague-Dawley rats underwent 1 week of chronic variable stress (CVS), with unhandled rats serving as controls. Independent groups of control and CVS rats were exposed to novel environment at 16 h, 4 days, 7 days, or 30 days after CVS. Marked reductions of c-fos mRNA expression in the CVS group persisted for at least 30 days within the paraventricular nucleus of the hypothalamus, and for at least 1 week in rostroventrolateral septum and lateral hypothalamus. Lower levels of c-fos mRNA expression were observed at 16 h recovery in the ventrolateral medial preoptic area, basolateral amygdala, anterior cingulate cortex, and prelimbic cortex. The results demonstrate long-term alterations in neuronal activation within neurocircuits critical for regulation of physiological and psychological responses to stressors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adrenocorticotropic Hormone / blood
  • Animals
  • Corticosterone / blood
  • Hypothalamo-Hypophyseal System / physiology*
  • Male
  • Paraventricular Hypothalamic Nucleus / metabolism*
  • Pituitary-Adrenal System / physiology*
  • Proto-Oncogene Proteins c-fos / biosynthesis*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Stress, Psychological / physiopathology*

Substances

  • Proto-Oncogene Proteins c-fos
  • RNA, Messenger
  • Adrenocorticotropic Hormone
  • Corticosterone