ACTIVITY OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS IS ELEVATED IN RATS WITH ACTIVITY-BASED ANOREXIA

Activity-based anorexia is characterized by suppressed food intake and excessive physical activity. These behaviors are typical of persons w ith anorexia nervosa. Activity of the hypothalamic-pituitary-adrenal a xis is known to be elevated in anorexia nervosa. We investigated the s tatus of this axis in activity-based anorexia. Meal fed-control (MFC) and meal fed-wheel running (MFWR) rats were given access to food for 9 0 min daily; MFWR animals were allowed access to an activity wheel the remainder of the day. The experiment terminated when MFWR animals rea ched 75% of pre-experimental body weight (males 3.9 +/- 0.3 d; females 4.2 +/- 0.2 d). Male and female MFWR rats consumed less food than MFC animals, while maintaining a high level of wheel running. Corticoster one concentrations were significantly elevated in MFWR animals. Cortic otropin-releasing hormone mRNA concentrations in the paraventricular n ucleus were not different. Relative adrenal gland weights were greater and thymus gland weights were lower in MFWR animals. Changes in food intake could not be explained by differences in insulin, glucose, beta -hydroxybutyrate or norepinephrine concentrations. Our results suggest increased activity of the hypothalamic-pituitary-adrenal axis in acti vity-based anorexia.