Intracerebroventricular administration of leptin increases anxiety-like behavior in female rats after semi-starvation--implications for anxiety in eating disorders.

BACKGROUND Patients with eating disorders often exhibit abnormal eating conditions like food restriction, adipocyte and body weight reduction, and pathologic anxiety-like behavior. The role of leptin, which is recognized as an adipocyte-derived hormone, on anxiety-like behavior in eating disorders is still unclear. METHODS We investigated the role of leptin on anxiety-like behavior with or without semi-starvation using the elevated plus-maze test in adolescent female rats. In our first experiment, anxiety-like behavior was evaluated with the elevated plus-maze test 30 min after intracerebroventricular administration of 3 microg of leptin or vehicle. In our second experiment, the rats were allowed access to food for only 2 hr each day for 7 days. Then, leptin or vehicle was administered to the rats after the last 2 hr feeding period, and anxiety-like behaviors were evaluated in the same way as in the first experiment. RESULTS In the first experiment, there was no difference between the anxiety-like behaviors observed after leptin administration and those seen after vehicle administration. Under the conditions of semi-starvation, however, the percentage of time spent in the open arms in the rats given leptin was lower than that in rats given vehicle. CONCLUSIONS These results suggest that leptin administration causes anxiety-like behavior only after semistarvation. Leptin might play an important role in pathologic anxiety-like behavior in eating disorders.