³H-normetanephrine uptake in rat brain slices. Relationship to extraneuronal accumulation of norepinephrine

³H-Normetanephrine accumulation in slices of rat brain was characterized and contrasted with ³H-norepinephrine accumulation. Initial rates of normetanephrine uptake were very rapid; accuumulated amine was not bound to particulate fractions and was easily washed out of the tissues. Unlike norepinephrine uptake, normetanephrine accumulation was unaffected by reserpine, was not stereospecific and was less affected by omission of glucose or sodium than was norepinephrine uptake. The cerebral cortex was the region of greatest normetanephrine accumulation whereas the corpus striatum accumulated norepinephrine to highest tissue: medium ratios. Several features of normetanephrine uptake in brain resembled both Uptake₂ of norepinephrine in heart and the extraneuronal uptake of norepinephrine in cocainized hearts. In rat brains in which the catecholamine nerve terminals were destroyed by intraventricularly administered 6-hydroxydopamine, endogenous norepinephrine was markedly reduced; ³H-norepinephrine accumulation by slices was decreased, and displayed characteristics more like normetanephrine uptake than like norepinephrine uptake in control animals.