Abstract
1. Intracisternally administered metaraminol, alpha-methyl-octopamine, alpha-methyl-m-tyramine, and alpha-methyl tyramine were found to lower brain noradrenaline without having an effect on brain dopamine.2. Amphetamine, mephentermine, and norephedrine had no effect on brain catecholamines after intracisternal injection.3. There was no reduction in brain dopamine content after intracisternal injection of alpha-methyl-m-tyramine, yet the resulting brain concentration of alpha-methyl-m-tyramine was several times higher than after intraperitoneal injection of alpha-methyl-m-tyrosine, which decreased brain dopamine.4. The decreased synthesis of labelled catecholamines from (14)C-tyrosine after alpha-methyl-m-tyrosine suggested that this compound inhibits tyrosine hydroxylase in addition to its action of displacing brain amines.