Abstract

Previous studies showed that both six- and fifteen-day-old pups exhibit changes in brainstem neural activity in response to glucose infusions, but the younger pups showed slightly less activity. Perhaps the neural signal triggered by nutrients enters the brain on young pups, but does not elicit changes in higher brain regions that are related to control of feeding. To investigate this possibility, young and old pups were compared for the effects of glucose infusions on activity in several forebrain regions. The effects of intestinal infusions of 0.8 M glucose and saline on the expression of c-Fos, a marker for neural activity, was analyzed in the supraoptic nucleus (SON), the paraventricular nucleus of the hypothalamus (PVN), the central nucleus of the amygdala (CeA), and the anterior and posterior arcuate in forebrains ofsix- and fifteen-day-old rat pups. Infusions of glucose into the duodenum resulted in a significant difference between treatments in fifteen-day-old pups' SON and CeA. Infusions of glucose in the duodenum of six-day- old rat pups showed no significant difference in any forebrain area when compared to saline infusions. Statistical tests comparing age and treatment group show that the SON is not responsible for the developmental change. Therefore, the neural connections to the CeA of fifteen- but not six-day-old rat pups may be responsible for the developmental change.