The Role of Corticotropin - Releasing Hormone (CRH) in the Tail Suspension Test (TST) - induced Sleep Alterations
Date Issued
2010
Date
2010
Author(s)
Hsu, Li-Ning
Abstract
Since hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis is common among depression patients, corticotropin-releasing hormone (CRH) and its character in spontaneous sleep modulation are thought to be related to the depression-induced sleep disturbances. In present study, we proposed that CRH plays a role in sleep disruption in depressive rats. We used tail suspension test (TST) as a stress-induced depression model, which included short-term stress group (TST day1) and long-term stress group (TST day8), to investigate the effects of CRH. Behavior of learning helplessness, one major indication of depression in animal, was evaluated during the TST.
In the first day after TST, both NREM sleep and REM sleep significantly decreased in the light period, and increased during the dark period. As TST continuously performed, sleep alterations gradually diminished while behavioral despair was progressively observed. By intracerebroventricular (ICV) injection of the CRH receptor antagonist, astressin, prior to the TST in the first day, we found that blocking CRH increased the struggling behavioral during TST and reversed the sleep alterations caused by short-term TST, indicating the involvement of CRH in short-term TST. ELISA results of corticosterone had shown the hyperactivity of HPA axis in rats suffered both from short-term and long-term TST. However, the behavioral despair in rats suffered from long-term TST was neither reversed by astressin nor by typical SSRI, fluoxetine. We also found that astressin had no effect on long-term TST-induced sleep alterations, while fluoxetine had shown slightly suppression of REM sleep during the light period. This observation is consistent with the effect of typical antidepressants. These results suggest that CRH may participate in the initiation of stressed behavior and the consequent sleep alterations but is not dominant in maintenance phase.
Subjects
depression model
tail suspension test
Type
thesis
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