EFFECTS OF LEPTIN ON FIRING RATE OF NEURONS FROM THE PREOPTIC AREA OF THE ANTERIOR HYPOTHALAMUS (PO/AH) IN RATS WITH NORMAL WEIGHT AND EXPERIMENTAL MODEL OF OBESITY

The adipose tissue-derived hormone leptin acts via its long receptor isoform in the brain to regulate energy balance and neuroendocrine function. The goal of this study is to investigate the effects of leptin on firing rate of neurons from preoptic area of the anterior hypothalamus (PO/AH) of rats with normal weight and experimental model of obesity. Extracellular recordings were obtained from PO/AH neurons in brain slice preparations (400 mu m) from Wistar rats, using conventional electrophysiological equipment. Leptin increased dose dependently the firing rate of PO/AH neurons from rats with normal weight whereas the firing rate of PO/AH neurons from rats with experimental model of obesity was not significantly altered by the action of leptin. The feeding of rodents with high-calorie diet leads to obesity, resulting in hyperleptinemia. The failure of elevated leptin levels to suppress feeding and mediate weight loss in common forms of obesity defines a state of so-called leptin resistance (attenuation of leptin signalling). This is the reason for reduced change in the firing rate upon administration of leptin on PO/AH neurons from rats with obesity. Our results provide future direction for further research on the complex interactions between thermoregulation and energy homeostasis.