Cytochemical localization of type-A and -B monoamine oxidase in the rat pineal gland.
In the mammalian pineal gland, serotonin (5-HT) is located both in the pinealocytes and in the noradrenergic nerve terminals. Pineal 5-HT can be metabolized by three different routes, one of these being its deamination, catalyzed by monoamine oxidase (MAO). MAO is known to exist as two isozymes, MAO-A and MAO-B. Using two different cytochemical methods at the ultrastructural level, we have localized the presence of MAO in the pineal gland of the rat. The use of selective inhibitors of A-type (clorgyline) and B-type (deprenyl) has shown that MAO-A is localized in the noradrenergic nerve terminals, while pinealocytes contain MAO-B. Taking into account that 5-HT is only deaminated by MAO-A, the specific association of each MAO isozyme with a defined cell type implicates that two cellular compartments are needed in the pineal gland for the biosynthesis of 5-methoxytryptophol and 5-methoxyindole acetic acid, while for the synthesis of melatonin and 5-methoxytryptamine just one cellular compartment, the pinealocyte, is appropriate.
Masson-Pévet
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M
CNRS-URA 226, Neurobiologie des fonctions rythmiques et saisonnières, Strasbourg, France.
Pévet
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P
D000818:Animals; D006651:Histocytochemistry; D008297:Male; D008854:Microscopy, Electron; D008995:Monoamine Oxidase / Q000378:metabolism*; D010870:Pineal Gland / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains
D008995:Monoamine Oxidase