ON SELECTIVE INHIBITION BY SOME MONOAMINE OXIDASE INHIBITORS OF DEAMINATION OF BIOGENIC MONOAMINES IN VIVO

Pargyline previously shown to be in vitro a selective inhibitor of deamination of tyramine by rat liver mitochondrial MAO causes in vivo a distinct selective inhibition of tyramine deamination in liver, kidney, and brain tissues of rat. No correlation could be found between the results of similar in vitro and in vivo experiments with phenelzine and nialamide. Modaline exhibits certain selectivity in its inhibitory effect in vivo on deamination of tyramine as compared with that of serotonin in liver and brain (but not in kidney) tissues; the compound Ro 4-2308, to the contrary, causes statistically significant prevailing inhibition in vivo of enzymatic deamination of serotonin in liver. Selective inhibition by MAOI of enzymatic deamination of various biogenic monoamines in vivo is possible but the patterns of this selectivity in various tissues could not be predicted on the basis of in vitro experiments with a standard preparation of liver mitochondrial MAO. © 1968.