Effects of chronic stress on food intake in rats: influence of stressor intensity and duration of daily exposure.

The effect of exposure to chronic intermittent stressors of differing intensities [handling, restraint, and immobilization (IMO)] and daily duration (15, 60, and 240 min of IMO) on changes in food intake was studied in adult male rats. Whereas handling did not caused anorexia, restraint slightly reduced food intake and IMO drastically reduced it. The effects were very similar after the 7th and 27th day of exposure to the stressors. Fourteen days of chronic IMO (2 h daily) resulted in decreased food intake as measured on days 1, 10, and 14 of treatment, the inhibition being slightly greater after the first stress session. The circadian rhythm of food intake, expressed as a percent of the total food eaten in a 24 h period, was found to be almost unaffected by chronic IMO, although IMO rats appeared to satiate sooner than control rats. Exposure of rats to chronic IMO (7 days) for 15, 60, and 240 min daily reduced food intake to the same extent in all IMO groups. Taken together, these results suggest that: a) the magnitude of the changes in food intake after chronic exposure to stressors is closely related to their intensity, and b) a severe stressor such as IMO reduces food intake to a certain level that was independent on its daily duration. After repeated exposure to the same stressor, only a slight tendency to recover normal food intake was observed.