Summary
It has been shown that 5 or 10 mg (-)deprenyl after i.v. application inhibited platelet MAO within 30 min. This effect correlated with the improvement of parkinsonian patients disability. Platelet MAO is purely of type B, thus resembling the human brain enzyme, which is 80% of type B. In other organs of the human MAO-A is of higher activity, thus it can oxidatively deaminate 5-HT, noradrenaline and tyramine in the periphery. The rather low peripheral side effects of (-)deprenyl can be explained by this fact. In vitro studies demonstrated that (-)deprenyl in comparison to d, l-tranylcypromine, clorgyline and harmaline is by far the most potent inhibitor of human brain MAO. Post-mortem studies in different human brain areas showed that there are differences in the behaviour of (-)deprenyl (10 mg) between short- and long-term treatment. Both show sufficient inhibition of DA-sensitive MAO (85–90%). However, when 5-HT is used as a substrate short-term treatment inhibits by about 40–50% whereas long-term treatment inhibits by about 65% which is higher than that mentioned before but not sufficient to increase brain 5-HT or decrease 5-HIAA. Therefore, long-term treatment with more than 1 mg/10 kg body weight could result in an accumulation of (-)deprenyl in the brain. Evidence for this derives from one parkinsonian patient, who was treated with 100 mg (-)deprenyl in which case both forms of the enzyme were inhibited sufficiently to increase DA and 5-HT in several brain regions.
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Riederer, P., Youdim, M.B.H., Rausch, W.D. et al. On the mode of action of L-deprenyl in the human central nervous system. J. Neural Transmission 43, 217–226 (1978). https://doi.org/10.1007/BF01246958
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DOI: https://doi.org/10.1007/BF01246958