Different responses of ventromedial hypothalamic neurons to leptin in normal and early postnatally overfed rats.

Leptin is crucially involved in the central nervous regulation of body weight. Neurons of the ventromedial hypothalamic nucleus (VMH) express leptin receptors and signal satiety with increase in their firing. Normally, leptin mainly activates VMH neurons. Rats grown up in small litters (SL) develop persistent hyperphagia and obesity throughout life. We studied single unit activity in hypothalamic brain slices of juvenile SL rats overweight due to early postnatal overfeeding (Mann-Whitney U-test, P < 0.001). VMH neurons of normal rats were mainly activated by leptin (Wilcoxon test, P < 0.05, n = 39), whereas neurons of overweight SL rats were mainly inhibited (Wt, P < 0.001, n = 33). This clearly altered response to leptin in neonatally overnourished rats might contribute to their persistent overweight throughout life.