Effects of Combined Treatment with Fluoxetine and Choline on the Retention of Passive Avoidance Learning after Chronic Mild Stress in Rat

Lee, Gi Chul; Cho, Sun Young; Lee, Jung Ho; Kim, Hyun Taek

Abstract

This study was performed to evaluate the effects of serotonin and choline on the memory function in rat model of depression. Chronic exposure to mild unpredictable stress was found to depress the consumption of sweet 1% sucrose solution in the Sprague-Dawley rats. We identified depressive behaviours in 27 Sprague-Dawley rats. Rats in experiments were stratified into 3 groups, ie, fluoxetine with choline, choline, and saline control. Memory function was evaluated by passive avoidance learning and retention tests. We evaluated how long memory retention would remain improved at training-testing intervals of 1 day, 1 week, 2 week, 3 week, and 4 week in depressive state of the Sprague-Dawley rats during 4 weeks of experimental drugs treatment. The results were as follows: 1) The fluoxetine with choline-treated group showed significant differences in the maintenance of retention from the saline control at 1, 2, 3, and 4 week training-testing interval. 2) The choline-treated group showed significant differences in the maintenance of retention from the saline control at 3 and 4 week training-testing interval. In summary, the combined treatment of fluoxetine with choline showed earlier effects on memory function compared with choline alone in the passive avoidance retention test in the animal model of depression. We suggest that there are synergistic interaction between serotonin and choline in the long term memory function in rat model of depression.