Studies on 5-fluoro-alpha-methyltryptamine and p-chloro-beta-methylphenethylamine: determination of the MAO-A or MAO-B selective inhibition in vitro.

To further clarify highly MAO-A- or -B-selective inhibitory properties of 5-fluoro-alpha-methyltryptamine (5-FMT) and p-chloro-beta-methylphenethylamine (p-CMPEA), we determined the types and K1 values of inhibition of rat brain MAO-A and -B activity in vitro. The kinetic data obtained showed that 5-FMT is a competitive MAO-A-selective inhibitor with about a 18,000-fold higher sensitivity than MAO-B. In contrast, p-CMPEA is a competitive MAO-B-selective inhibitor with about a 620-fold higher sensitivity. Based on the present findings of highly MAO-A- or -B-selective inhibition, these two compounds might prove to be of value in in vivo studies.