Involvement of brain trace amines in the behavioural effects of phenelzine

The MAO inhibitor phenelzine (PLZ) at a dose of 25 mg/kg does not affect the behavior of rats. In contrast, the equivalent dose of a deuterated analog (alpha, alpha, beta, beta-tetradeutero-PLZ, d4PLZ) elicits a biphasic behavioral syndrome in rats. In an attempt to correlate changes in cerebral monoamines with behavior, the concentration of various amines were measured at various times after the administration of either d4PLZ or PLZ (25 mg/kg). In general, PLZ and d4PLZ caused elevations in brain amine levels, particularly in the time period 2-12 hours after drug administration. Furthermore, d4PLZ increased the concentrations of serotonin (5-HT), phenylethylamine (PE), tryptamine (T), meta-tyramine (mTA), and 3-methoxytyramine (3-MT) to a greater extent than PLZ. Since the time course of behavioral excitation closely parallels the elevations in T and PE levels in the brain and since the percentage increases in PE and T levels following d4PLZ compared to PLZ treatment were substantially greater than those of the other amines, it was postulated that PE and T are involved in d4PLZ-induced behaviors.