About: Monoamine oxidase is a(n) research topic. Over the lifetime, 6903 publication(s) have been published within this topic receiving 205159 citation(s). The topic is also known as: MAO & amine:oxygen oxidoreductase (deaminating).
01 Jan 1964-Acta Physiologica Scandinavica
TL;DR: The results suggest that p -chlorophenylalanine may effect 5HT depletion by inhibiting the biosynthesis of this monoamine, possibly by blocking tryptophan hydroxylation.
Abstract: p -Chlorophenylalanine has been found to be a potent and selective depletor of brain serotonin (5HT) in mice, rats and dogs. Brain 5-hydroxy-3-indolylacetic acid (5HIAA) content was also depleted by the drug, but catecholamine concentrations were only slightly decreased. Peripheral stores of 5HT were also lowered. In rats, p -chlorophenylalanine reduced the normal increase in brain 5-hydroxyl-3-indolyl compounds following L-tryptophan loading (without apparently affecting tryptophan uptake into brain), completely prevented the increase in brain 5HT accompanying inhibition of monoamine oxidase by pargyline and blocked the increase in brain 5HIAA usually observed after reserpine treatment. p -Chlorophenylalanine slightly diminished the usual increase in brain 5HT in rats following 5-hydroxytryptophan (5HTP) administration, but decreased the rate of disappearance of excess 5HT and antagonized the increase in brain 5HIAA. p -Chlorophenylalanine did not inhibit monoamine oxidase or 5HTP-decarboxylase in vitro and exerted no effect on monoamine oxidase or 5HTP decarboxylase activity of rat tissues in vivo. In contrast, p -chlorophenylalanine inhibited liver tryptophan hydroxylase in vitro and strongly suppressed the tryptophan- and phenylalanine-hydroxylating capabilities of livers of rats treated with it. These results suggest that p -chlorophenylalanine may effect 5HT depletion by inhibiting the biosynthesis of this monoamine, possibly by blocking tryptophan hydroxylation. A blockade of uptake of amino acid precursor might also contribute to the effect of decreasing 5HT biosynthesis. The slow depletion (2-3 days) of brain 5HT induced by p -chlorophenylalanine suggests that an active metabolite might be formed. p -Chlorophenylpyruvic acid exerted essentially the same pharmacologic effects as the amino acid, but it cannot be ascertained at present whether it is the active metabolite because of the interconversion of α-amino acids and α-keto acids in vivo. p -Chlorophenethylamine may be excluded as the metabolite responsible for the action of p -chlorophenylalanine because of the brief duration of the amine in brain and the short lasting, nonselective decrease of both 5HT and norepinephrine produced by the amine. A study of structural variation in the phenylalanine series indicated a specific requirement of a single chlorine substituent in the para position for potent in vivo activity. Rats treated with p -chlorophenylalanine displayed few apparent signs, and certainly not sedation. p -Chlorophenylalanine did not block characteristic signs elicited by reserpine or tetrabenazine in rats. Accordingly, the central actions of reserpine and reserpine-like drugs may possibly be dissociated from both 5HT concentrations and the formation of new 5HT in brain.
01 Jul 1968-Biochemical Pharmacology
TL;DR: The hypothesis that in the enzyme prepared, the MAO is a binary system of enzymes each of which has a detectably different sensitivity to this particular inhibitor, is put forward and evidence after dialysis supports this hypothesis.
Abstract: The inhibition of monoamine oxidase (MAO) in vitro and in vivo by N-methyl-N-propargyl-3(2,4-dichlorophenoxy) propylamine hydrochloride (M&B 9302) is described. The kinetics of the MAO-M&B 9302 reaction show a unique abnormality as compared with known inhibitors. The plot of percentage inhibition against concentration of M&B 9302 does not show a simple sigmoid curve, but reveals a pair of sigmoid curves joined by a horizontal section where the inhibition is invariant. The hypothesis that in the enzyme prepared, the MAO is a binary system of enzymes each of which has a detectably different sensitivity to this particular inhibitor, is put forward and discussed. Evidence after dialysis supports this hypothesis.
23 Jun 1995-Science
TL;DR: Pup behavioral alterations, including trembling, difficulty in righting, and fearfulness were reversed by the serotonin synthesis inhibitor parachlorophenylalanine, and adults manifested a distinct behavioral syndrome, including enhanced aggression in males.
Abstract: Deficiency in monoamine oxidase A (MAOA), an enzyme that degrades serotonin and norepinephrine, has recently been shown to be associated with aggressive behavior in men of a Dutch family. A line of transgenic mice was isolated in which transgene integration caused a deletion in the gene encoding MAOA, providing an animal model of MAOA deficiency. In pup brains, serotonin concentrations were increased up to ninefold, and serotonin-like immunoreactivity was present in catecholaminergic neurons. In pup and adult brains, norepinephrine concentrations were increased up to twofold, and cytoarchitectural changes were observed in the somatosensory cortex. Pup behavioral alterations, including trembling, difficulty in righting, and fearfulness were reversed by the serotonin synthesis inhibitor parachlorophenylalanine. Adults manifested a distinct behavioral syndrome, including enhanced aggression in males.
TL;DR: The neurotoxic chemical MPTP is metabolized by rat brain mitochondrial fractions at a rate of 0.91 +/- 0.02 nmoles/mg protein/min, and the major metabolite has been identified as the 1-methyl-4- phenylpyridinium species.
Abstract: The neurotoxic chemical MPTP (1-methyl-4-phenyl-1,2,4,5-tetrahydropyridine) is metabolized by rat brain mitochondrial fractions at a rate of 0.91 +/- 0.02 nmoles/mg protein/min. The major metabolite has been identified as the 1-methyl-4- phenylpyridinium species. This biotransformation process is blocked by 10(-7) M deprenyl and pargyline. MPTP itself inhibited the metabolism of benzylamine by brain mitochondrial fractions. These results are discussed in terms of possible bioactivation mechanisms that may be associated with the neurodegenerative properties of MPTP .