SUMMARY1. Solutions of glucose or other carbohydrates were administered during the dark or light period of the circadian cycle to rats which had been only briefly deprived of food.2. Food was restored to the animals at various times after administration of a glucose load by stomach tube. With delays between loading and access to food of up to 3 hr by night and 2 hr by day, subsequent food intake was less than intake after non-nutritive loads.3. Measurement of the glucose content of the gastrointestinal tract at various times after glucose loading showed that this depression of intake was still apparent even when the rat was offered food some time after complete absorption of the stomach load.4. Infusion of a glucose solution into the duodenum or the hepatic portal vein also inhibited subsequent food intake.5. In all cases, the inhibition of food intake was expressed as a decrease in the size of the first meal after restoring access to food.6. These results provide the first demonstration that the entry of normal amounts of carbohydrate into the body by the physiological route is followed by a depression of food intake which lasts until after absorption is complete.

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When D-glucose-C14 was placed in the oropharyngeal cavity of anesthetized rats with the esophagus ligated, generally no radioactivity was detectable in the brain (or liver) after 5 or 10 min. When rats were allowed to drink radioactive starch or were stomach-tubed radioactive glucose, .2%-! .3% of the radioactivity was recovered in the brain after 5 min. The medial diencephalon had a high-uptake rate but was not unique in that respect. It is concluded that if there is a "direct" (transbuccal) route to the brain, it is negligible compared with the well-known intestinal route. Also, on an empty stomach at least, an initial sample of glucose from food starch can reach the brain within a few minutes from the start of a meal.