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Effect of Chronic Mild Stress on AT1 Receptor Messenger RNA Expression in the Brain and Kidney of Rats

Objective The purpose of the study was to determine whether exposure to chronic mild stress (CMS) affects expression of angiotensin II Type 1a receptor (AT1aR) messenger RNA (mRNA) in the brain and kidney. Methods Male Sprague-Dawley rats were divided into an unchallenged control group, which remained at rest, and an experimental group, exposed to CMS produced by a series of unexpected, disturbing stimuli applied at random over a period of 4 weeks. After sacrificing the animals, samples of the septal/accumbal and hypothalamic/thalamic diencephalon, brain medulla, cerebellum, and the renal medulla were harvested for determination of AT1aR mRNA. Results Expression of AT1a receptor mRNA was significantly greater in the rats in the CMS condition than in the controls (septal/accumbal diencephalon: 1.689 [0.205] versus 0.027 [0.004], hypothalamic/thalamic diencephalon: 1.239 [0.101] versus 0.003 [0.001], brain medulla: 2.694 [0.295] versus 0.028 [0.003], cerebellum: 0.013 [0.002] versus 0.005 [0.001; p < .001 for all comparisons], and renal medulla: 409.92 [46.92] versus 208.06 [30.56; p < .01]). There was a significant positive correlation between AT1a mRNA expression in the septal/accumbal diencephalon and brain medulla (p < .025). Conclusions The results provide evidence that CMS significantly enhances expression of the AT1aR gene in the brain and kidney and indicate that changes in expression of AT1aR mRNA in different brain regions during CMS may be causally related. It is suggested that the up-regulation of AT1a receptors by chronic stress may potentiate negative effects of angiotensin II in pathologies associated with activation of the renin-angiotensin system.