Physiology & Behavior 69 (2000) 359–362 0031-9384/00/$ – see front matter © 2000 Elsevier Science Inc. All rights reserved. PII: S0031-9384(99)00258-9 Leptin-induced decrease in food intake in chickens D. Michael Denbow a, *, Sharonda Meade a , Adam Robertson a , John P. McMurtry b , Mark Richards b , Chris Ashwell b a Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306, USA b Growth Biology Laboratory, United States Department of Agriculture, Agricultural Research Service, Bldg 200 BARC-East, Beltsville, MD 20705, USA Received 22 September 1999; received in revised form 10 November 1999; accepted 20 December 1999 Abstract The effect of intracerebroventricular (i.c.v.) injection of leptin was investigated using broiler and Single Comb White Leghorn (SCWL)-type chickens. These represent relatively fast- and slow-growing birds, respectively. The i.c.v. injection of leptin decreased food intake in both broilers and Leghorns in a dose-dependent manner. The most efficacious dose appeared to be 10 g in both types of chick- ens. Water intake was generally not affected by leptin, indicating that this effect was not due to general malaise. It appears that leptin can act within the central nervous sytstem of birds to decrease food intake. © 2000 Elsevier Science Inc. All rights reserved. Keywords: Leptin; Food intake; Water intake; Chickens 1. Introduction It has been known for years that endogenous lipid stores are well regulated [20]. Although it is unlikely that such regulation can be explained by a single gene, the cloning of the ob gene encoding for leptin has shed some light on mechanisms regulating lipid deposition [29]. In mammals, it appears that mutations in either leptin [23] or its receptor [8,22] results in changes in lipid stores and food intake. Leptin is thought to act as a signal between the peripheral lipid stores and the central nervous system [7], gaining ac- cess to the brain at the arcuate nucleus and choroid plexus by a specific transport system [3]. Intracerebroventricular (i.c.v.) or intrahypothalamic injections of leptin have been reported to decrease food intake in a variety of mammals in- cluding mice [8], rats [9], pigs [4], and monkeys [26]. Leptin probably acts by altering neuropeptide Y expression and re- lease from neurons originating in the arcuate nucleus [24,27]. The gene encoding leptin in chickens has recently been cloned [2,25]. Unlike in mammals, the gene is expressed not only in adipose tissue, but also in liver. Interestingly, both adipose tissue [21] and liver [19] are believed to be periph- eral sites involved in food intake regulation. It is well documented that the modern broiler and Leg- horn are relatively fast-growing and slow-growing, respec- tively [5]. It has been shown that the mechanisms regulating food intake differ between Leghorns and broilers, presum- ably because of differential genetic selection for growth rate [10]. It is reasonable to expect that a signal originating from adipose or hepatic tissue would act similarly in birds and mammals. Recently, however, it was reported that i.c.v. injec- tions of leptin did not reduce food intake in young chickens [6]. The purpose of the present study was to determine if leptin acts within the central nervous system of chickens to alter food intake in two types of chickens differing in growth rate. 2. Materials and methods 2.1. Animal preparation Broiler and Leghorn cockerels obtained on the day of hatch were reared in heated batteries with raised wire-bot- tom floors until 4, and 7 weeks of age, respectively. There- after, they were moved to individual cages. Broilers have been selected for rapid body weight gain [13], whereas Leg- horns have been indirectly selected for slow growth [16]. These ages were selected so that the birds would be of similar weight at the time of the experiments. A mash diet (20% crude protein, 2864 kcal/kg metabolizable energy) and water were provided ad lib consumption, and lighting was continuous. After being moved to individual cages, each bird was anaesthetized with sodium pentobarbital (25 mg/kg), and a 23-gauge thin-walled stainless steel guide cannula was ste- reotaxically implanted into the right lateral ventricle as de- * Corresponding author. Tel.: 001-540-231-6843; Fax: 001-540-231- 3713 E-mail address: denbowdm@vt.edu