Abstract

The technique of [^l4C]2-deoxyglucose (2DG) autoradiography was used to analyze metabolic changes in the central nervous system associated with meal termination in six-day-old rat pups. The infant rat terminates and initiates meals in response to cues produced, almost exclusively, by gastric distension. In this investigation, there were two treatment groups: plugged gastric fistulas (distension), and unplugged fistulas (sham control). The pups were injected with 2DG and allowed to finish a meal. Afterwards, we sacrificed the rats and froze the brains. Brains were then sliced and exposed to X-ray film. We videographed the brain slice images (X-ray film) and then, using Drexel's BRAIN image analysis software, compared the brain sections between treatment groups and looked for areas of changed metabolic neural activity in the normal-fed rat relative to the sham-fed rat. Results indicate that gastric distension mediates meal termination in six-day-old rats by stimulating the caudal NTS activity which, in turn, inhibits ventral reticular formation activity. The inhibition of the reticular activity removes the stimulation of the oral motor nuclei which would otherwise elicit oral motor behaviors (i.e, mastication, swallowing, lapping). Once we understand the rudimentary ingestive controls in the six-day-old pup, our investigations might focus on more complex ingestive controls in the older preweanling pup and mature rat. These studies might provide insight on the complex functions of human ingestive behaviors, since the rat is such a useful model for the study of mammalian ingestive behavior.