Objective To observe the changes of behavior and the brain structrue in rats with chronic unpredictable mild stress and to explore its role in the process.
Methods Fifteen Wistar rats were set as the depression model group, to them the chronic unpredictable mild stress was used to support. Another 15 rats without any stimulation were set as the control group. The performance, body weight, the coefficient of brain, the consumption of liquid, plasma cortisone levels, and the changs of the brain structure in both groups were observed.
Results During eight weeks, in the depression model group, the increase of body weight reduced, and the coefficient of brain decreased (P<0.01). Scores of horizontal and vertical movements, consumption of sucrose solutions and the frequency of cleaning action were significantly reduced (P<0.05 or P<0.01), whereas pure water consumption increased as compared with the control group (P<0.01). Plasma corticosterone levels reached the peak at the second week (P<0.01), but showed a declining trend at the third week. The ultrastructure changes in the hippocampus were observed by electronmicroscope.
Conclusion The repeated chronic unpredictable mild stress stimulation can induce long-time changes in acts and activities in rats and damage their hippocampus structure. It may be one of the mechanisms in depression development.
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