MAO-B activity in depression and anxiety disorders

Monoamine oxidase (MAO) is a mitochondrial enzyme responsible for the oxidative deamination of catecholamines and indolamines (Alexopoulos et al 1984). Plate!ets contain only MAO-B, whereas human brain contains both MAO-A and MAO-B (Po~,rier et al 1987). The kinetics of platelet MAO-B are believed to be similar to central turnover of monoamines (Georgotas et al 1986), but Young and colleagues (1986) found no connection between platelet and brain MAO-B. Nevertheless, this controversial area has been implicated in attempts to identify a biological marker tbr the evaluation of the size or capacity of the central serotonin system (Hailman et al 1990). In this study we examined platetet MAO-B activity as a biological marker tbr depressive and anxiety disorders, giving par.icular attention to its relation to age of onset.