INGESTION AFTER STRESS - EVIDENCE FOR A REGULATORY SHIFT IN FOOD-REWARDED OPERANT PERFORMANCE

Stress usually decreases food consumption and body weight in rats. Acc ording to the regulatory shift hypothesis, these effects reflect order ly changes in how animals meet their metabolic needs in dangerous circ umstances. This interpretation was tested by examining food-rewarded o perant performance before and after stress. Six fixed-ratio (FR) sched ules were used in a within-subject design in Experiment 1, and a betwe en-subject design (FR2 versus FR32) was used in Experiment 2. In both experiments, exposure to 100 inescapable tailshocks reduced response r ate on smaller schedules, whereas responding on larger schedules was u nchanged or increased. This pattern can be interpreted as a decrease i n preferred eating rate and an improvement in the behavioral regulatio n of food intake. Milder stressors generally had less impact but did i ncrease preferred feeding rate, an effect potentially related to stres s-induced eating in other paradigms. This study provides evidence that strong stressors reorganize ingestive behavior, as predicted by the r egulatory shift hypothesis. (C) 1997 Academic Press.