A proposed method for the determination of cerebral regional intermediary glucose metabolism in humans in vivo using specifically labeled 11C-glucose and positron emission transverse tomography (PETT). I. An animal model with 14C-glucose and rat brain autoradiography.

Based upon data obtained with our arterio-venous technique for the determination of cerebral metabolism in humans in vivo we have proposed a method for the determination of cerebral regional intermediary glucose metabolism in humans in vivo using specifically labeled 11C-glucose and positron emission transverse tomography (PETT). In it we would give the subject successive intravenous injections of [3,4-11C] glucose, [2,5-11C] glucose and [1-11C] glucose. There would be a 30 min period of continuous PETT measurements following each injection and a 2 hr interval after the first and second injections. The data would be used with suitable equations and algorithms to estimate for each specific region of the subject's brain the dynamics of the Embden-Meyerhof-Parnas (EMP) and the tricarboxylic acid cycle (TCA) metabolic pathways and the incorporation of glucose carbons into lactate, and the extent of dilution of glucose carbons into lactate, and the extent of dilution of glucose carbons in traversing the TCA with their subsequent incorporation into other carbon pools of the brain (ie, glutamate, glutamine, GABA, alanine). Using 14C as a model for 11C and autoradiographs made with rat brain slices, we have produced an animal model to demonstrate the feasibility of our proposed method. The resulting autoradiographs have provided evidence of the validity of the predictions made from our arterio-venous data. The model was employed to show the selective reductions in the rates of incorporation of specific carbon atoms of glucose into regions of the rat brain and evidence of altered metabolic pathways following a single electroconvulsive shock (ECS) and after a series of nine ECS.