Abstract

This study investigated the effects of food restriction on Neuropeptide Y (NPY) staining in the arcuate nucleus of lactating rats to evaluate a role for NPY in the maintenance of lactational diestrus in food restricted rats. NPY staining was compared on days 15, 20 and 25 of lactation between animals fed ad libitum (AL) and animals food restricted on days 8-14 postpartum (FR). To determine the contribution of nursing underfed pups to any differences observed, litters were switched daily between an additional AL and FR group from day 15 postpartum and dams were sacrificed on day 20 postpartum. Twenty four hrs. prior to sacrifice animals received 1$\mu$g of colchicine icv. Animals were perfused and their brains were processed for NPY immunocytochemistry. FR dams had a higher number of NPY stained cells in the arcuate nucleus on day 15 of lactation than AL dams, and this effect persisted for five days after refeeding (p $<$.05). Increases in NPY staining in food restricted rats were unrelated to the nutritional status of their litters. Finally, data revealed that dams that remained in lactational diestrus on day 25, tended to have more NPY-stained cells in the arcuate nucleus than dams that had shown an estrous smear (p =.08). These results indicate that food restriction affects NPY immunoreactivity in the arcuate nucleus and the time course of these changes suggest that NPY may play a role in prolonging lactational diestrus.