Neurochemical, hormonal, and behavioral effects of chronic unpredictable stress in the rat

Abstract

The high comorbidity of anxiety and depression suggests a potential degree of commonality in their etiologies. The chronic unpredictable stress (CUS) model effectively replicates depressivelike phenotypes; however, the ability of CUS to produce anxiety-like behaviors has not been adequately addressed. Using the CUS paradigm (2 stressors per day for 10 days) in adult Sprague Dawley rats we identified behavioral, hormonal, and neurochemical changes one day after the cessation of treatment. Stress attenuated weight gain throughout the study and increased locomotor activity one day after treatment, but had no effect on anxiety-behavior as measured by the elevated plus maze. In addition, plasma corticosterone levels were positively correlated with hypothalamic serotonin (5-HT) activity one day after stress treatment as determined by the ratio of the metabolite 5-hydroxyindoleacetic acid (5-HIAA) to the parent compound (5-HIAA/5-HT ratio). These data suggest behavioral phenotypes associated with depression, but not comorbid anxiety, emerge in the immediate period after cessation of stress and that stress related physiology is related to 5-HT activity in the hypothalamus.

Role of Aspirin and Dexamethasone against Experimentally Induced Depression in Rats

“…There was no effect of anti-inflammatory treatments in the anxiety-based parameters like number of transitions in the light/dark box, number of cut-offs in the photoactometer and time spent in the open arm of the elevated plus-maze test. The results were ambiguous and non-conclusive and were in agreement with previous studies [45,53,54]. Contradictory to the above, aspirin treatment in the CMS group for about 28 days showed noteworthy antidepressant effect through the rise in sucrose preference, brain serotonin levels and decline in serum cortisol and immobility in the CMS group treated with aspirin.…”

Behavioural and transcriptional effects of escitalopram in the chronic escape deficit model of depression

“…It is known that patients suffering from depression may experience weight loss, and a decrease in weight gain has been reported in other stress-based animal models of depression [44,45]. Raone and co-workers failed to observe any difference after a 4-week stress exposure in the CED model of depression (even though the body weight of stressed animals was lower with respect to naive rats; [9]), our findings suggest that the weight gain was permanently altered by the exposure to the unavoidable stress session, and stressed animals although they increased their weight during the course of the experiment, showed a slower rise with respect to naive animals.…”

Behavioural and neurobiological consequences of 2 different chronic stressors in rats

“…The chronic headache group did not show any significant differences compared to the control group in the EPM; although they both showed more anxiety-like behaviour at 1-day and 1-week intervals, the difference was not statistically significant. Although depressive-like phenotypes after a CMS model in rodents have been repeatedly and conclusively reported, results about anxiety-like behaviour after a CMS model are inconclusive (10). These discrepancies appear to be caused by the application of different anxiety models at different time intervals following exposure to CMS.…”

“…Phenotypes of depression such as decreased weight gain (4), altered locomotor activity (5), decrease in sexual behaviour (6,7), altered diurnal rhythms, and sleep disturbances with decreased REM latency and increased number of REM episodes (8,9) have also been reported after CMS. Results about anxiety-like behaviour after chronic mild stress in rodents are inconclusive (10).…”