Measurement Of Anhedonia In The Chick Anxiety-Depression Model

Anhedonia, the loss of pleasure in previously pleasurable activities, is one of the cardinal features of depression. To further validate the chick anxiety-depression model, the current study aimed at quantifying anhedonia as well its reversal with pharmaceuticals. The first goal was to identify a measure to quantify the display of anhedonia in chicks following exposure to an isolation stressor, the chick anxiety-depression model. All experiments involved a baseline and test measurement either after removal from the home cage (No Test) or exposure to the isolation apparatus with conspecifics and mirrors (Social) or individually (Isolated). Experiment 1 used a straight maze with start and goal latency serving as the dependent measures. Isolated chicks expressed delays in start latency compared to No Test chicks, which is interpreted as anhedonia-like behavior. Experiment 2 used a modified sucrose preference task to assess sucrose preference and the number of drinking events for water and sucrose. Consistent with the rodent literature, results shodecreased sucrose preference in Isolated chicks compared to No Test chicks. Experiment 3 involved measurement of behavior in a dust bath apparatus. Contrary to predictions, limited behavior was observed in the apparatus. The second goal of the present study was to be able to reverse the display of anhedonia-like behavior, as measured in the straight alley maze, with pharmaceutical manipulation. Experiment 4 involved administration of vehicle, 10 or 15 mg/kg Imipramine prior to exposure to the isolation apparatus folloby testing in the straight alley maze. Both 10 and 15 mg/kg Imipramine were shown to alleviate the onset of behavioral despair in the isolation test. The 15 mg/kg Imipramine dose also alleviated the display of anhedonia in the straight alley maze. Experiment 5 involved the administration of vehicle, 5 or 10 mg/kg Ketamine prior to exposure to the isolation apparatus folloby testing in the straight alley maze. Neither 5 nor 10 mg/kg Ketamine were able to alleviate the onset of behavioral despair or anhedonia as assessed in the straight alley maze