A growing body of evidence suggests that maternal undernutrition sensitizes the offspring to the development of energy balance metabolic disorders such as type 2 diabetes, dyslipidemia and obesity. The present study aimed at examining the impact of maternal undernutrition on leptin plasma levels in newborn male rats and on the arcuate nucleus proopiomelanocortin (POMC) and neuropeptide Y (NPY) neurons that are major leptin targets. Using a model of perinatal maternal 50% food-restricted diet (FR50) in rat, we evaluated leptin plasma levels and hypothalamic POMC and NPY gene expression from postnatal day (PND) 4 to PND30 in both control and FR50 offspring. In control rats, a postnatal peak of plasma leptin was observed between PND4 and PND14 that reached a maximal value at PND10 (5.17 +/- 0.53 ng/mL) whereas it was dramatically reduced in FR50 pups with the higher concentration at PND7 (0.93 +/- 0.23 ng/mL). In FR50 animals, using semi-quantitative RT-PCR and in situ hybridization, we showed that hypothalamic POMC mRNA level was decreased from PND14 until PND30, whereas NPY gene expression was not significantly modified. In PND21 FR50 animals, we observed strikingly reduced immunoreactive -endorphin nerve fibers projecting to the hypothalamic paraventricular nucleus without affecting NPY projections. Our data showed that maternal undernutrition drastically reduces the postnatal surge of plasma leptin disturbing, particularly the hypothalamic wiring as well as the gene expression of the anorexigenic POMC neurons in male rat pups. These alterations might contribute to the adult metabolic disorders resulting from perinatal growth retardation.