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PubMed1980

Monoamine oxidase inhibitors and histamine metabolism.

In rat, histamine metabolism is altered by some nonspecific inhibitors of monoamine oxidase (MAO) such as iproniazid, and, to a lesser extent, tranylcypromine. Type A MAO inhibitors, such as clorgyline and MD780515, do not seem to interfere with the metabolism of histamine. Deprenyl, a type B MAO inhibitor, shows some inhibition which is, however, much lower than that observed with iproniazid. The strong effect of iproniazid is probably due to its DAO inhibiting properties.

Animals↗
PubMed1977

Monoamine oxidase activity in blood platelets from autistic children.

In order to evaluate the possible abnormality in monoamine oxidase (MAO) activity in early infantile autism, blood platelet samples were obtained from 20 autistic children, aged 2--12 years. MAO activity, measured fluorometrically using serotonin as substrate, was 5.24 +/- 1.65 (Mean +/- Standard Deviation) nM/MG protein/hour in these autistic children. This value was not significantly different from either that in 30 age-matched normal children or that in 39 nonautistic children with various psychiatric and neurological disorders, although autistic children had higher platelet serotonin concentration than these nonautistic individuals.

Autistic Disorder↗
PubMed1983

Kinetic evaluation of platelet monoamine oxidase following relaxation in chronic anxiety.

The effect of relaxation training, utilizing EMG biofeedback, on platelet monoamine oxidase (MAO) activity was examined in patients with a history of chronic anxiety. Anxiety scores and MAO activity were significantly lowered after 4 weeks of therapy. Kinetic studies, using phenylethylamine as substrate, indicated a significant increase of the Km constant while the Vmax showed no significant or consistent variation. It is thought that this phenomenon represents an adaptive response by the individual to maintain a homeostatic level of the biogenic amines.

Adult↗
PubMed2001

Inhibitory effects of sanguinarine on monoamine oxidase activity in mouse brain.

The effects of benzophenanthridine alkaloids, such as sanguinarine and chelidonine, on monoamine -oxidase (MAO) activity in mouse brain were investigated. Sanguinarine showed an inhibitory effect on MAO activity in a concentration dependent manner (53.4% inhibition at 25 microM). However, chelidonine did not inhibit MAO activity. The IC(50) value of sanguinarine was 24.5 microM. Sanguinarine inhibited non-competitively MAO activity using kynuramine as a substrate. The K(i) value for sanguinarine was 22.1 microM. These results suggest that sanguinarine partially contributes to the regulation of catecholamine content.

Alkaloids↗
PubMed1995

Clinical efficacy of reversible and selective inhibitors of monoamine oxidase A in major depression.

This article reviews efficacy studies of the reversible selective inhibitor of monoamine oxidase A (MAO-A) moclobemide, which has now received extensive evaluation. Placebo-controlled trials have shown it clearly to be effective. In comparisons with tricyclic and similar antidepressants and with serotonin reuptake inhibitors, it has been found of equal efficacy to these standard drugs. Because of previous suggestions that older MAO inhibitors are particularly effective in depressions characterized as atypical, the effects in subtypes are of particular interest. The evidence indicates that moclobemide is effective in typical severe depression with melancholia rather than being limited to less typical subtypes.

Antidepressive Agents, Tricyclic↗
PubMed1988

Effect of selective monoamine oxidase inhibitors on rat pineal melatonin synthesis in vitro.

Freshly cultured pineal glands respond to the monoamine oxidase A (MAO A) inhibitor clorgyline and to high concentrations of the MAO B inhibitor, deprenyl, with an increase in serotonin N-acetyltransferase activity and N-acetylated indoles and a fall in 5-hydroxylated serotonin degradation products. Glands cultured for 48 hours before challenge respond less. Response is absent in glands cultured for 72 hours and in glands from ganglionectomized animals cultured for 48 hours before challenge. These data are consistent with the hypothesis that these MAO inhibitors stimulate melatonin synthesis by protecting norepinephrine from degradation.

Animals↗
PubMed1981

Effect of chlorpromazine treatment on monoamine oxidase activity in platelets isolated by the Corash method.

The effect of chlorpromazine treatment on platelet monoamine oxidase (MAO) activity was compared in platelets isolated by the Corash method, which harvests essentially all the platelets in a blood sample, and a single centrifugation method, which yields 45-65% of the platelets. A highly significant decrease in platelet MAO activity following chlorpromazine was found in platelets obtained from the same subjects by both methods. The decrease observed by the two methods was significantly correlated. These results indicate the degree of decrease in MAO activity associated with chlorpromazine is not due to isolation of a subpopulation of platelets with low MAO activity by the single centrifugation method.

Blood Platelets↗
PubMed1980

Platelet monoamine oxidase in affective illness and alcoholism.

The authors review the literature on the relationship of platelet monoamine oxidase (MAO) to affective disorders and alcoholism. Although some studies have reported an association between low platelet MAO and bipolar illness, others have failed to replicate this finding. Alcoholism has been related to affective disorders, and it is of note that three studies have found low MAO in alcoholics. Given the physiological consequences of alcoholism, however, the interpretation of these findings is unclear. The authors conclude that nonspecificity of low platelet MAO as a possible correlate of bipolar affective disorder, as well as schizophrenia, increases the burden of proof necessary before findings of low platelet MAO can be accepted as primary.

Alcoholism↗
PubMed1985

Biochemistry and physiology of monoamine oxidase (MAO) activity in the ring dove (Streptopelia risoria). I. Characteristics of MAO activity in vitro.

Monoamine oxidase (MAO) activity was measured in ring dove (Streptopelia risoria) tissues using a fluorometric assay with kynuramine as substrate. Harmaline inhibited MAO activity in a time-dependent manner, and preincubation of enzyme with the drug did not affect its activity. Pargyline produced a slow-onsetting inhibition of activity which was enhanced by preincubation of enzyme and inhibitor. Harmaline displayed reversible non-competitive inhibition of MAO activity. Oxygen is also a substrate for dove MAO, and the reaction apparently involves "ping-pong", double-displacement kinetics. Dove MAO activity is temperature-dependent, with an activation energy of 13.1 kcal/mole.

Animals↗
PubMed1996

Selective inhibitors of monoamine oxidase. 3. Structure-activity relationship of tricyclics bearing imidazoline, oxadiazole, or tetrazole groups.

Inhibition of monoamine oxidase A (MAO A) is believed to cause antidepressant and possibly antianxiety effects. The previous paper had developed structure-activity relationships (SAR) for in vitro MAO A inhibition by tricyclic N-arylamides. It is shown in this paper that the same in vitro SAR can be carried over to tricyclics whose potentially toxic amide function is replaced by an appropriately substituted imidazoline, a 1,2,4- or 1,3,4-oxadiazole, or an alkylated tetrazole moiety. Dialysis of the inhibitor from the enzyme was used as a measure of reversibility which correlates with a low ability to cause a blood pressure rise with ingested tyramine ("cheese effect").

Imidazoles↗
PubMedDate not supplied

[Calcium and ammonia stimulate monoamine oxidase A activity in brain mitochondria].

The effect of ammonia and calcium on the activity of monoamine oxidase (MAO) was studied. The enzyme activity in non-synaptic brain mitochondria isolated from rats administered with ammonium acetate was assayed by release of H2O2 using spectrophotometry. The effect of calcium on MAO was assayed directly after addition of Ca2+ to the non-synaptic mitochondria isolated from the forebrain of the control rats. Both ammonium acetate injection in vivo and Ca2+ addition in vitro stimulated the activity of MAO A but not that of MAO B in mitochondria. This is the first evidence that ammonia and Ca2+ regulate MAO A in non-synaptic mitochondria in the forebrain and can contribute to oxidative stress in the neurons via MAO A activation.

Acetates↗
PubMed1996

maoB, a gene that encodes a positive regulator of the monoamine oxidase gene (maoA) in Escherichia coli.

The structural gene for copper- and topa quinone-containing monoamine oxidase (maoA) and an unknown amine oxidase gene have been located at 30.9 min on the Escherichia coli chromosome. Deletion analysis showed that the unknown gene was located within a 1.1-kb cloned fragment adjacent to the maoA gene. The nucleotide sequence of this fragment was determined, and a single open reading frame (maoB) consisting of 903 bp was found. The gene encoded a polypeptide with a predicted molecular mass of 34,619 Da which was correlated with the migration on a sodium dodecyl sulfate-polyacrylamide gel. The predicted amino acid sequence of the MaoB protein was identical to the NH2-terminal amino acid sequence derived by Edman degradation of the protein synthesized under the self-promoter. No homology of the nucleotide sequence of maoB to the sequences of any reported genes was found. However, the amino acid sequence of MaoB showed a high level of homology with respect to the helix-turn-helix motif of the AraC family in its C terminus. The homology search and disruption of maoA on the chromosome led to the conclusion that MaoB is a transcriptional activator of maoA but not an amine oxidase. The consensus sequence of the cyclic AMP-cyclic AMP receptor protein complex binding domain was adjacent to the putative promoter for the maoB gene. By use of lac gene fusions with the maoA and maoB genes, we showed that the maoA gene is regulated by tyramine and MaoB and that the expression of the maoB gene is subject to catabolite repression. Thus, it seems likely that tyramine and the MaoB protein activate the transcription of maoA by binding to the regulatory region of the maoA gene.

Amino Acid Sequence↗
PubMed1983

Distribution of monoamine oxidase activity in tissues of the urodeles Ambystoma tigrinum (tiger salamander) and Necturus maculosus (mudpuppy).

1. Monoamine oxidase (MAO) activity was determined fluorometrically in tissues of adult mudpuppies, and pre- (young) and post- (adult) metamorphic tiger salamanders. 2. From responses to specific inhibitors it was determined that 95% activity was MAO type A in all tissues. 3. In young salamanders MAO activity was greater in brain and intestine of males than of females, and was considerably higher in kidney of both sexes and in intestine of males compared to adults. 4. MAO activity was distributed differently in the mudpuppy compared to the salamander. Intestine and liver contained high activity and brain had relatively little MAO activity compared to salamander. 5. The apparent Michaelis constant of MAO activity in the different groups and tissues was generally similar, suggesting a similarity of the MAO molecule.

Aging↗
PubMed1989

[Inhibitory effect of hypoxanthine on monoamine oxidase activity].

Hypoxanthine was demonstrated to have a dose-dependent inhibitory effect on type B monoamine oxidase (MAO-B) activity in liver and brain tissues, and slight inhibitory effect on type A MAO(MAO-A) activity when given orally to mice at doses of 25-500 mg/kg. When mice were given orally hypoxanthine 500 mg/kg, MAO-A and -B activities were all inhibited significantly 16 hours after administration, but the inhibitory action on MAO-A was weaker. Subcutaneous injection of the agent also produced obvious inhibition of MAO activity in the liver but no significant influence on MAO activity in brain tissue was observed. In vitro experiment showed that the action of hypoxanthine on MAO-B was competitive inhibition and that on MAO-A was competitive mixed with noncompetitive inhibition.

Animals↗
PubMed1990

Effect of selective monoamine oxidase A and B inhibitors on footshock induced aggression in paired rats.

Effects of a selective monoamine oxidase (MAO)--A inhibitor, clorgyline, a selective MAO-B inhibitor, deprenyl, and a non-selective MAO inhibitor, nialamide, were investigated on footshock-induced aggression (FIA) in paired rats. The doses and pretreatment times of the inhibitors used were based on an earlier reported in vivo dose-response and time-course study. In addition, apomorphine, a dopaminergic receptor agonist, and beta-phenylethylamine, a preferred substrate for MAO-B, were also used to garner corroborative evidence. The results of the study indicate that selective MAO-A inhibitors are likely to attenuate FIA by augmenting central serotonergic activity, while selective MAO-B inhibitors accentuate the behaviour by facilitating dopaminergic activity. A permissive role for noradrenaline could not be delineated by the available data.

Aggression↗
PubMed1995

Association analysis of a polymorphism of the monoamine oxidase B gene with Parkinson's disease in a Japanese population.

The polymorphic allele of the monoamine oxidase B (MAO-B) gene detected by polymerase chain reaction (PCR) and single-stranded conformation polymorphism (SSCP) was associated with Parkinson's disease (PD) in Caucasians. We characterized this polymorphic allele, allele 1, of the MAO-B gene using direct sequencing of PCR products. A single DNA substitution (G-A), resulting gain of Mae III restriction site was detected in intron 13 of the MAO-B gene. The allele associated with PD in Caucasians was twice as frequent as in healthy Japanese, but the association of the allele of the MAO-B gene was not observed in Japanese patients with PD.

Adult↗
PubMed1989

Histochemical detection of monoamine oxidase and alcohol dehydrogenase activities in the Syrian hamster Harderian glands: existence of a sexual dimorphism.

Monoamine oxidase (MAO) and alcohol dehydrogenase (AD) activities were studied histochemically in the Syrian hamster Harderian gland using tryptamine as substrate and Nitroblue Tetrazolium as the final electron acceptor. No dark: light-related changes were observed. Male type I secretory cells showed an intense MAO reaction. Female type I cells exhibited a moderate MAO activity. Both male and female glands showed a moderate/intense AD-positive reaction. Male type II cells were lacking MAO and AD activities. MAO activity found in the hamster Harderian glands corresponded mainly to MAO type A since treatment with chlorgyline (0.01, 0.1 and 0.5 mM) totally inhibited it. The possible role of these two enzymes in Harderian gland indolalkylamine metabolism is discussed.

Alcohol Dehydrogenase↗