NOREPINEPHRINE AND 3,4DIHYDROXYPHENETHYLAMINE TURNOVER IN GUINEA PIG BRAIN IN VIVO.

By administering C(14)-la-beled tyrosine or H(3)-labeled 3,4-dihy-droxyphenylalanine to guinea pigs it has been possible to achieve sufficient labeling of the norepinephrine and dopamine in the brain to permit measurement of their turnover rates. The half-life of brain dopamine was about 2.5 hours. The half-life of norepinephrine was about 4 hours, suggesting a rate of synthesis of at least 0.03 to 0.04, microg/g per hr or 2.4 microg/day for the whole guinea pig brain.