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Psychology | Social and Behavioral Sciences


Linda Tennison, Psychology


The current study examined the validity of the chronic mild stress and learned helplessness models of depression in addition to testing the efficacy of the tricyclic antidepressant imipramine. Thirty-six male albino rats were randomly assigned to three experimental conditions: control, chronic mild stress (CMS), and learned helplessness (LH). Half of the animals in each condition received IP injections of imipramine at 10 mg/kg/day, and the other half received equal volumes of isotonic saline. All animals were weighed daily throughout experimentation. The CMS animals were chronically stressed for a period of five weeks after which learned helplessness was induced in the LH group through one two hour shock session. All groups were tested weekly for sucrose consumption and following the initiation of learned helplessness behavioral tests were conducted. A Morris Water Maze and open field test were used to evaluate the spatial memory and anxiety behavior respectively of the rats. The results of this study indicate that the CMS model of depression is not very reliable in that sucrose consumption did not decrease even after 6 weeks of testing. The animals given imipramine showed significant growth delays which is indicated by their delayed weight gain in comparison to saline animals. LH rats showed more hyperactivity in the open field test on days 2, 3, and 7 of testing and deficits in spatial memory on the first day of Morris Water Maze testing.

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