The ailTI of this study was ta cSlablish whether or nol a link ean be made belween nutritional conditions in carly life, food preferences and hYPolhalamic NPY system functioning throughout life. The offspring of dams fcd on unbalanced diet, either a high carbohydrat diet (HC) or a high fat diet (HF), during the gestation and lactation pcriods were compared to rats obtained From dams fed on a well-balanccd diet (C). First, we studied the growth of male offspring from binh until adulthood. The growth of the HC group was similar ta the control group. The HF rats \veighcd less than the other groups at binh, and this difference persisted, until laler in life. At weaning, hypoinsulinemia and hypoglycaemia WOlS established in the HF group in comparison to the C and HC groups. These di fferences disappear at adulLhood. After that, we studied the evolution of diet preferences in the three groups Olt different stages of development. The control group did indeed show a preference for the carbohydrate diet.From the 30th day of life. Such a preference was not observed in the two other groups at 30 d~lYS of age, but it appeared later in lire, at 3 months for the HC group and 4 monlhs for the HF group. In addition the nycthemeral rhythm of the consumplion of eaeh macronutriment was modified in the HC and HF groups, in comparison to the C group. Conceming the :NPY system, the principal hypothalamic axis of NPY action fonned by the arcuate and paraventricular nucleus (ARC-PVN) seemed ta be unaltered at wcaning and during adullhaod, with respect ta ilS NPY cancenlratian and mRNA expression. At wcaning, in lllC venlromedian nucleus (cenler of saliety), the NPY was abnormally high in the HC groups. This phenomenon disappeared al adulthood. However, the NPY system remained altered in adulthood, as is shown by the alteralion of the reactivity of the l\rpy system after cenlral NPY injection and the study of hypathalamic release of NPY in vivo. The study of the rcactivity ta l\rpy injection showed that, at adulthoad, the HC rats were Jess sensitive to exogenous NPY than the twa other groups, while the HF group was particularly sensitive. The dynamic study by push-pull technique showed that, after intraperitonea! 2-DeoxyGlucose injection, which staps glucose uli!ization, the HC group reacted by increasing NPl' liberation. On the contrary, the injection of mercaploacetate, which stops fatty acid axidation in mitochondria, did not have any cffcct on this group, but induced increased l\'PY rclcase in the HF group.Therefore, the l\rpy system is differently modified in the HC and the HF group, these alteratiol1s are not due ta the same reasons : They Céln be induccd by physiologiea! disordcrs in the HF group, but not in the HC group.To a certain extent, wc can considcr lh~ll an adaptative mechanism occured in carly life as a means at counteract the unbalanced dicl. \\'ell-balanccd diet givcn to the offsprings after weaning facilitated this proccss, particularly in the HC group. By cxtrapolating these resulls in man, \\C can venture ta say that the predisposition to metabolic disordcrs causcd by mothcr's unbalanced diet can be partly