Pharmacology, biochemistry, and behavior
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Pharmacol. Biochem. Behav. · May 1996
Effect of chronic mild stress on circadian rhythms in the locomotor activity in rats.
The purpose of this study was to assess whether the chronic mild stress (CMS) procedure, as a realistic animal model of depression, affects the rhythms of the locomotor activity in rats. Rhythm parameters (period, mesor, amplitude, acrophase, and percent rhythm) were estimated from the best-fitted cosine function curves. Period is the length, mesor is the mean level, amplitude (A) is the extent, acrophase is the timing of the rhythm; percent rhythm represents the variability estimated by the cosine regression and expressed as a percentage of the total variability of raw data. ⋯ In contrast to the results from LL, the cosine curves from DD were similarly shifted in relation to the subjective light-dark cycle. After a restoration of the LD cycle the levels of the 24-h activity of both groups became equal in the 13th week, but the light and dark phase differences between the groups were still statistically significant (p < 0.05). The present results indicate that CMS exerts distinct and prolonged disturbances of the diurnal and circadian rhythms of the locomotor activity in the rats.
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Pharmacol. Biochem. Behav. · May 1996
ReviewActivation of the HPA axis by immune insults: roles and interactions of cytokines, eicosanoids, glucocorticoids.
It is now well established that challenges to the immune system (e.g., infection, inflammation) initiate diverse changes in neuroendocrine function, the most overt of which is activation of the hypothalamo-pituitary-adrenocortical (HPA) axis. The glucocorticoids that are released as a consequence fulfill a vital role in the maintenance of homeostasis that is effected in part through their ability to quench the immune/inflammatory response and thereby prevent them accelerating to a point where they become hazardous to the host. This article discusses the putative mechanisms by which immune insults stimulate the HPA axis, with particular reference to the roles and interactions of the interleukins, eicosanoids and glucocorticoids.