Effects of undernourishment on the hypothalamic orexinergic system

The present study examined the effects of a severely restricted diet during the pre- and postnatal periods with later nutritional rehabilitation on orexin hypothalamic neurons in male and female Wistar rats. Immunocytochemistry was used to reveal orexin-immunoreactive (orexin-ir) cells in the ventromedial hypothalamus (VMH), dorsomedial hypothalamus (DMH), lateral hypothalamic area (LH) and the perifornical nucleus (PF). Dietary restriction decreased the number of orexin-ir cells in the LH, whereas DMH or PF orexin-ir populations were not affected in either male or female rats. Nutritional rehabilitation resulted in a differential recovery that depended on the period during which rehabilitation occurred and on the sex of the animal. In summary, our study suggests that the hypothalamic nuclei implicated in eating behavior present a differential vulnerability to adverse environmental conditions during development. Specifically, among the studied nuclei only the LH orexin-ir cells were sensitive to severe food deprivation during development in male and female rats. These results suggest that starvation interferes with developmental events that occur during CNS sexual differentiation.