Is 5-Methoxytryptamine the B-Type Fluorophore in Rat Brain?

Dewhurst, W. G.; McKim, H.R.

doi:10.1159/000117677

Cited by 5 publications

(1 citation statement)

References 6 publications

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“…5-MT has furthermore been found to share some properties with indoleamine hallucinogens and has therefore been considered as a potential endogenous psychogenic compound (De Montigny and Aghajanian, 1977). The published data regarding the endogenous presence of 5-MT in animal tissues are, however, conflicting (Green et al, 1973;1975;Meek and Neckers, 1977;Prozialeck et al, 1978;Bosin et al, 1979;Dewhurst and McKim, 1979). There seems to be convincing evidence that 5-MT is present endogenously in mammalian tissues, while there is disagreement as to the quantitative levels which may be ascribed at least in part to the different analytical techniques used.…”

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confidence: 99%

In Vivo Formation of 5‐Methoxytryptamine from Melatonin in Rat

Beck

Jonsson

1981

Journal of Neurochemistry

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Deacetylation of melatonin to 5-methoxytryptamine (5-MT) in vitro and in vivo was investigated in rat liver and brain tissue, using a gas chromatographic--mass spectrometric 5-MT assay method. In vitro incubation of liver but not brain (hypothalamic, Mesencephalic) slices with melatonin led to a concentration-dependent formation of small amounts of 5-MT; the conversion being 0.3--0.8%. In vivo administration of melatonin resulted in a dose-dependent formation of 5-MT in small quantities in the liver. The time course showed a peak maximum within 0.5 h, with a rapid decline; the half-life being about 1 h. 5-MT could be detected in both the blood and the hypothalamus after in vivo injection of melatonin. The time course of 5-MT in the blood was similar to that in the liver, but 5-MT could only be detected in the hypothalamus after large doses shortly after the melatonin injection. MAO had to be inhibited both in the in vitro and in vivo experiments in order to recover 5-MT, indicating that formed 5-MT is normally rapidly metabolised by MAO. It is concluded that a small fraction of melatonin can be converted to 5-MT by deacetylation (by aryl acylamidase) in the liver in vivo, constituting a minor pathway. Such a pathway could not be demonstrated in the brain. Trace amounts of 5-MT previously reported to be present in various tissues could originate from deacetylation of melatonin in the liver and possibly some other peripheral organs known to contain the deacetylating enzyme. The present results indicate that peripherally formed 5-MT, a psychoactive compound, is unlikely to have any effect on brain function under normal circumstances.

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In Vivo Formation of 5‐Methoxytryptamine from Melatonin in Rat

Beck

Jonsson

1981

Journal of Neurochemistry

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5-Methoxyindoles in pineal gland of cow, pig, sheep and rat

Beck

Jonsson

Lundman

1981

Naunyn-Schmiedeberg's Arch. Pharmacol.

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The occurrence and concentration of the four 5-methoxyindoles: 5-methoxtryptamine, 5-methoxytryptophol, 5-methyoxyindole-3-acetic acid and melatonin in the pineal gland of pig, cow, sheep and rat was investigated. The analytical method involved the use of deuterated analogues as internal standards and capillary column gas chromatography - mass spectrometry. The analyses of pineal glands obtained during the morning hours revealed the presence of 5-methoxyindole-3-acetic acid and melatonin in nmoles/g and 5-methyoxytryptophol and 5-methoxytryptamine in pmoles/g amounts in pig, cow and sheep. In Wistar and Sprague-Dawley strain of rat, melatonin was present at a concentration of about 0.5 pmoles/pineal, a level which was elevated more than five times by treatment with a monoamine oxidase inhibitor. 5-Methoxytryptamine was found at a concentration of about 0.03 pmoles/pineal, and was elevated by monoamine oxidase inhibition.

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