The acute effect of monoamine oxidase inhibitors on serotonin conversion to melatonin

Gregory F. Oxenkrug

in 5-Hydroxytryptamine in Psychiatry

Published in print February 1991 | ISBN: 9780192620118
Published online March 2012 | e-ISBN: 9780191724725 | DOI:
The acute effect of monoamine oxidase inhibitors on serotonin conversion to melatonin

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Monoamine oxidase (MAO) inhibitors were introduced as antidepressants about thirty years ago. The pharmacological mechanism of their antidepressant effect was related to the inhibition of MAO activity and limitation of the catabolism of the monoamines, serotonin (5-hydroxytryptamine, 5-HT) and noradrenaline. Both monoamines play an important role in the regulation of melatonin biosynthesis from serotonin. This process involves the N-acetylation of serotonin to form N-acetylserotonin (NAS), which is catalysed by N-acetyltransferase (NAT). The synthesis of NAS is triggered by noradrenaline stimulation of the pinealocyte adrenoceptors (mainly β1 receptors). The next step is methylation of NAS to form melatonin, which is catalysed by hydroxyindole-O-methyltransferase. The inhibition of MAO by MAO inhibitors is acute: it occurs within hours of the administration of a single dose. Both tricyclic and heterocyclic antidepressants increase the levels of melatonin in human plasma after administration of a single dose. A single electroconvulsive shock almost doubled rat pineal TV-acetyltransferase activity and the concentrations of melatonin and serotonin. This chapter concentrates on studies of the acute effect of MAO inhibitors on melatonin biosynthesis.

Keywords: monoamine oxidase; antidepressants; catabolism; N-acetylation; pinealocyte adrenoceptors; melatonin biosynthesis

Chapter.  5089 words. 

Subjects: Neuroscience

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