PALATABLE FOOD INDUCES AN APPETITIVE BEHAVIOR IN SATIATED RATS WHICH CAN BE INHIBITED BY CHRONIC STRESS

An experimental model for the study of antidepressant treatments was d evised by exploiting the response maintained by vanilla pellets in rat s freely fed on a standard diet. The apparatus used was a Y-maze and t he rats were trained, during 10-12 consecutive sessions, to earn a van illa pellet placed at the end of one of the two divergent arms. Animal s exposed to repeated unavoidable stressors during the training phase did not develop the appetitive behaviour. Rats previously trained on t he Y-maze, however, did not modify their performance under the effect of repeated stressors. Long-term treatment with imipramine and fluoxet ine, given for 2 weeks before training and during the whole of the tra ining phase, was able to antagonize the disrupting effect of chronic s tress on the acquisition of the Y-maze. Finally, vanilla pellet consum ption in trained animals induced a consistent increase in extraneurona l dopamine in the nucleus accumbens, as measured by microdialysis.