Stressors in the learned helplessness paradigm: effects on body weight and conditioned taste aversion in rats.

Changes in body weight and taste aversion in the learned helplessness paradigm were examined. In Experiment 1, adult male Sprague-Dawley rats drank saccharin or a control solution, followed by either 100 inescapable shocks or simple restraint. Rats were weighted daily and were tested for saccharin aversion two days after the stress session. Shocked rats gained less weight in the days after stress than restrained controls. Saccharin aversion was apparent only among rats that had consumed saccharin before the stress session. Experiment 2 examined whether control over shock affected body weight or taste aversion. Home-cage controls were included to assess the effects of restraint alone. In addition, the combined effects of shock and a toxin on aversion were studied. Rats drank saccharin solution, followed by escapable or inescapable shock, restraint, or no treatment. Then half of each group was injected with saline; the other half was injected with lithium chloride. As in Experiment 1, shock reduced body weight relative to restraint or no treatment, and shock produced a taste aversion among saline-treated rats. However, shock attenuated the aversion produced by lithium chloride, as did simple restraint. There were no differences in body weight or taste aversion between escapably and inescapably shocked rats. These results suggest a role for stress in the anorexia and weight loss associated with clinical depression and may have implications for theories of learning and learned helplessness.