Monoamine oxidase activity in relation to psychiatric disorders: The state of the art

Publisher Website
Google Scholar
Abstract
Monoamine oxidase (MAO; E.C. 1.4.3.4) activity in platelets is one of the few hitherto known biological markers which might be useful in clinical psychiatric practice. Thus, as is discussed in more detail below, there are obvious connections between platelet MAO activity and certain personality traits. In this way, however, low (and possibly high) platelet MAO activity is a marker for “vulnerability” rather than for illness. The present knowledge about relationships between temperament and central monoaminergic activity does not permit any definite conclusions about which monoamine system is involved. Available data, however, favour the notion that the activity of the serotonin system is most closely connected to the personality traits of interest. Thus, the simplest interpretation would be that there is a positive correlation between central serotonergic activity and platelet MAO activity. Such an interpretation is supported by the findings of a positive correlation between CSF levels of 5-HIAA and platelet MAO activity. It is, however, unlikely that the platelet MAO activity can in any way, influence central monoaminergic activity. Therefore, we assume that the platelet MAO activity merely acts as a genetic marker for some property of the central serotonin system, such as the density, size or functional capacity. The role of brain tissue MAO in this context is even more difficult to assess. There are, however, results about changes in brain MAO activity in the same direction as the platelet enzyme in some disorders, and, furthermore, brain serotonin uptake seems to be correlated to brain MAO activity. Thus, central serotonergic “capacity” as well as platelet and brain MAO activities seem to be regulated by some common factor. One such common factor might be prenatal testosterone imprinting, which seems to cause life-long effects on both laterlization, which might be of importance to some personality traits, and on MAO activity.