The route of glucose to the brain from food in the mouth of the rat

Conducted an experiment with 28 male albino Sprague- Dawley rats. It was found that when dextroglucose-C14 was placed in the oropharyngeal cavity of anesthetized Ss with the esophagus ligated, generally no radioactivity was detectable in the brain (or liver) after 5 or 10 min. When Ss were allowed to drink radioactive starch or were stomach-tubed radioactive glucose, .2-1.3% 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.