A Technique for Assaying the Kinetics of Norepinephrine Metabolism in the Central Nervous System in Vivo

An in-vivo technique has been developed for assaying the kinetics of norepinephrine (NE) metabolism in the central nervous system. H3 NE is injected into the cisterna magna of dogs, concomitant with an intravenous infusion of C14 NE. Urine is collected every hour for a period of 12 hr. and levels of H3, C14 NE, and various metabolites determined. By a series of mathematical steps, based upon the solutions of kinetic models, functions are obtained from which estimates are made, for any time, of the amount of H3 metabolite in urine which is due to degradation of H3 NE within the central nervous system per se. The experimental results obtained with a series of dogs agree well with data obtained by more direct means.