Platelet monoamine oxidase B activity in Parkinson's disease: a re-evaluation

An increase in platelet monoamine oxidase (MAO) B activity in drug-free parkinsonians (n = 6) compared with healthy controls (n = 10) has been confirmed using both phenylethylamine (PEA) and dopamine as substrates, reaching statistical significance in the case of PEA oxidising activity (p < 0.05). Thus, certain reports of raised platelet MAO B activity towards PEA but decreased activity towards dopamine in parkinsonians, raising the possibility of the existence of an abnormal form of MAO B in this condition, cannot be supported.