CALL FOR PAPERS Physiological Regulation of Appetite Long-Evans and Sprague-Dawley rats exhibit divergent responses to refeeding after caloric restriction

Evans, S. A., M. M. Messina, W. D. Knight, A. D. Parsons, and J. M. Overton. Long-Evans and Sprague-Dawley rats exhibit divergent responses to refeeding after caloric restriction. Am J Physiol Regul Integr Comp Physiol 288: R1468–R1476, 2005. First published February 3, 2005; doi:10.1152/ajpregu.00602.2004.—Mature male Sprague-Dawley (SD) and Long-Evans (LE) rats were instrumented with telemetry transmitters for measurement of heart rate (HR) and housed in room calorimeters for assessment of food intake and oxygen consumption (V̇O2) at standard laboratory temperatures (23°C) to examine physiological responses to caloric restriction (CR; 60% of baseline ad libitum calories for 2 wk) and refeeding. Ad libitum controls had stable food intake (84–88 kcal/day) and gained weight at rates of 3–4 g/day. Groups from both strains assigned to CR exhibited similar patterns of weight loss and reductions in V̇O2 and HR. Upon refeeding, SD rats exhibited a mild, transient hyperphagic response (1 day) accompanied by sustained suppression of V̇O2 and HR that remained evident 8 days after refeeding. In contrast, LE rats exhibited sustained daily hyperphagia that persisted 8 days after refeeding and was accompanied by a complete restoration of HR and V̇O2. The lower HR and V̇O2 observed during refeeding in SD rats were not due to reduced locomotor activity. The results reveal a strain-dependent divergent response to recovery from CR. We conclude that during recovery from CR, homeostatic stimulation of appetite or suppression of energy expenditure may occur selectively to restore body weight.