Benzylhydrazine-A selective inhibitor of human and rat brain monoamine oxidase

Benzylhydrazine (BzNNH₂) was shown to inhibit irreversibly human brain type A and type B monoamine oxidase (MAO) as measured by 5-hydroxytryptamine (5-HT) and phenylethylamine (PEA) deamination, respectively. The concentrations required to inhibit these isoenzymes in vitro were 2.7 × 10^-7M and 1.7 × 10^-8M, respectively. Inhibition of 5-HT deamination was essentially non-competitive, whereas that for PEA approached uncompetitive kinetics. BzNNH₂ also inhibited rat brain MAO in vivo, 50 per cent inhibition of the A and B forms of MAO occurring at injected doses of 0.72 and 0.39 mg/kg respectively. These results indicate that BzNNH₂ preferentially inhibits the B form of both human and rat brain MAO.