A Comparison of the Effects of Acute and Chronic Administration of Phenelzine and Tranylcypromine on Brain Concentrations of 2-Phenylethylamine, p-Tyramine and Tryptamine in the Rat

Abstract

The “trace” amines 2-phenylethylamine (PE), p-tyramine (p-TA) and tryptamine (T) have been implicated in the etiology of a number of psychiatric disorders, including depression (Dewhurst, 1968; Boulton and Milward, 1971; Sabelli and Mosnaim, 1974; Sandler et al., 1979). It is now well known that monoamine oxidase (MAO) inhibitors, drugs that are used in treatment of psychiatric disorders, cause rather dramatic increases in brain concentrations of these trace amines (Boulton et al., 1973; Axelrod and Saavedra, 1975; Philips et al., 1980; Philips and Boulton, 1979; McKim et al., 1980). However, these reports on MAO inhibitors are acute studies, and there is a paucity of information available on the effects of chronic administration of MAO inhibitors on brain levels of these compounds. In recent years, we have conducted experiments on the effects of chronic injection of two clinically efficacious MAO inhibitors, tranylcypromine (TCP) and phenelzine (PLZ) on brain levels of PE (Baker et al., 1982), p-TA (Baker et al., 1983) and T in the rat. The findings from these experiments are reviewed here.