Abstract

The responsiveness of rat pups to ingested nutrients appears to develop between the age of birth and weaning. By fifteen days of age, pups show a marked decrease in their amount of intake following intestinal infusions of 0.6M glucose. In this study, the metabolic activity in the brainstem of fifteen-day old rat pups was examined under two conditions. In one condition, pups were intestinally infused with 0.6M glucose, and in the other, pups were infused with isotonic saline.

Pups were deprived of food and water, and polyethylene cannulas were implanted into the duodenum. Pups were then given injections of [14C] 2-DG and allowed to eat sweetened Half and Half solution. They received infusions of glucose or saline for the first eight minutes of the feeding test. After testing, pups were sacrificed, their brains were removed and frozen, and the brains were sectioned. Brain slices were then exposed to X-ray film for ten days to produce autoradiograms.

The autoradiograms were entered into a computer and analyzed using image-analysis hardware and software. Analysis of various brain levels and regions showed effects in an apparent auditory pathway, including the LL, IC, etc., and in an oral-facial neural pathway, including the SP50, PrH, etc. These results, in conjunction with behavioral observations, appear to reveal neural correlates that underlie nutrient-induced satiety.