1. Chronic stress produces enduring decreases in novel stress-evoked c-fos mRNA expression in discrete brain regions of the rat.
- Author
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Ostrander MM, Ulrich-Lai YM, Choi DC, Flak JN, Richtand NM, and Herman JP
- Subjects
- Adrenocorticotropic Hormone blood, Animals, Corticosterone blood, Male, RNA, Messenger metabolism, Rats, Rats, Sprague-Dawley, Hypothalamo-Hypophyseal System physiology, Paraventricular Hypothalamic Nucleus metabolism, Pituitary-Adrenal System physiology, Proto-Oncogene Proteins c-fos biosynthesis, Stress, Psychological physiopathology
- 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.
- Published
- 2009
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