Effect of chronic intraperitoneal injections of leptin on hypothalamic neurotensin content and food intake

This study was intended for the investigation of the effects of chronic inj ections of leptin for 7 days on food intake and hypothalamic neurotensin (N T). Leptin treatment significantly reduced food intake [144.3+/-2.5 g (L) v s. 156.7+/-2.5 g (C); P=0.002] and body weight gain [23.7 g+/-1.0 g (L) vs. 31.5+/-1.3 g (C); P=0.003]. NT concentration was lower in the lateral hypo thalamus (LH) of leptin-treated rats than in the control ad libitum fed rat s (-30%; P<0.05). The same diminution was observed in pair-fed rats (-27%; P<0.05). This diminution was therefore related to the decrease in food inta ke rather than to a direct effect of leptin. As the LPI was the only area w here NT was modified, it appears that among the hypothalamic nuclei involve d in the regulation of feeding behavior it is the most sensitive area to a low energy depletion. Therefore, it might play a specific role in triggerin g the mechanisms necessary to restore body weight and/or energy balance. (C ) 2000 Elsevier Science B.V. All rights reserved.