Wheel running induces conditioned taste aversion in rats trained while hungry and thirsty.

Rats while both hungry and thirsty were given three exposures to either a salt solution or a sour solution followed by a brief period of wheel running. On other occasions, these rats while hungry and thirsty were exposed to the alternate solution without wheel running. Conditioned aversion to the flavor paired with wheel running was evident after two pairings. During final tests with each solution, the rats were thirsty but not hungry. As expected, conditioned aversion to the particular flavor paired with wheel running was still observed despite a change in deprivation state from training to test. These results indicate that wheel running can induce sickness. Because sickness suppresses eating, activity anorexia in rats and some forms of anorexia nervosa in humans may be caused, at least in part, by sickness.