The Effect of Hypoglycemia on the Metabolism of the Brain1

The brain in its metabolic requirements is unique among organs. The available data indicate that the brain is the only organ to acquire its energy from the exclusive oxidation of carbohydrate. The evidence for this lies chiefly in the observation that the respiratory quotient of the brain in situ is unity (1, 2). The brain, moreover, has but little store of carbohydrate (3), hence, the fact that it absorbs both glucose and lactic acid from the cerebral blood (1, 4) is in conformity with the respiratory quotient of unity. Even in diabetes the respiratory quotient remains unchanged (1, 2). Furthermore, there is no evidence that fat enters into the respiratory metabolism of the brain, for acetone substances are neither poured into the bloodstream during diabetes, nor absorbed for oxidation from ketonemic blood traversing the brain (5). In an organ so dependent on carbohydrate and, indeed, the carbohydrate of the blood, hypoglycemia may have deep-seated results. The present investigation is an attempt to determine the effects of hypoglycemia on the metabolism of the brain. Such studies, moreover, may throw light on the mechanism of the response of the patient with schizophrenia to insulin injections.