Intracerebroventricular injection of murine leptin enhances the postprandial metabolic rate in the rat

Energy balance is achieved by means of a concomitant control of both food i ntake and energy expenditure. Leptin, synthesized in the adipose tissue, ac ts on brain structures and lowers body weight by inhibiting food intake and in parallel by enhancing energy expenditure i.e. metabolism or one of its components. Recording distinctly these components allowed us to assess the effect of an acute intracerebroventricular injection of leptin on both feed ing pattern and background metabolism (i.e. energy expenditure free from th e part of locomotor activity), respiratory quotient, feeding-related metabo lism and locomotor activity-related metabolism. Leptin injection to Sprague -Dawley male rats induced an inhibition of feeding that began 90 min after the treatment and lasted 1 h before to return to the control feeding patter n level. Considering this late behavioral effect, it appeared that leptin m ay act during the postprandial period so that we recorded the different met abolic parameters following a 3 g calibrated meal itself preceded by leptin vs. artificial cerebrospinal fluid injection. Postprandial respiratory quo tient was rapidly lowered in leptin-treated animals and subsequent backgrou nd metabolism increased for 6 h. Thus it appeared that leptin increased the duration of the postprandial metabolic rate via the recruitment of endogen ous fat stores. Enhancement in the thermic effect of food may be the reason for feeding behavior inhibition to be delayed. (C) 2000 Elsevier Science B N. All rights reserved.