PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “MONOAMINE OXIDASE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,747 records · Page 97Linked to original sources
PubMed1988

Basic and clinical aspects of the activity of the new monoamine oxidase inhibitors.

The clinical relevance of the neurobiochemical and pharmacological properties of the new generation of monoamine oxidase inhibitors (MAOIs) is reviewed and discussed. The most distinctive characteristics of these drugs are the selectivity, competitive nature and reversibility of their MAO-inhibiting action. The most selective MAO-A inhibitors are moclobemide and brofaromine, with ratios between their MAO-A and MAO-B inhibiting potency (estimated in in vitro assays) of 1: greater than or equal to 1000 and 1:500, respectively, whereas the least selective drug is cimoxatone with a ratio of 1:66. If in vitro findings are considered, the most potent MAO-A inhibitor seems to be cimoxatone and the least potent toloxatone. After oral administration, however, cimoxatone, brofaromine and moclobemide appear to be about equally effective in inhibiting brain MAO-A. All these drugs are short acting and their MAO-inhibiting action is reversible within 24 h or, in the case of brofaromine, 48 h. Due to the selectivity and reversibility of the MAO-A inhibition, they were found to be less likely to induce large increases in the pressor responses to tyramine, both in animals and in man. In patients treated with 150 mg/day for 4 weeks, brofaromine, which appears to be the best-characterized drug in this respect, produced about a 4-fold increase in sensitivity to tyramine. Although the clinical antidepressant efficacy of these drugs remains to be confirmed in more extensive studies, based on their neurobiochemical and pharmacological properties, clear advantages in respect to their side-effect profiles are to be expected in comparison with the classical MAOIs.

Animals↗
PubMed2005

Changes in platelet monoamine oxidase activity, cholesterol levels and hyperactive behaviour in adolescents over a period of three years.

Platelet monoamine oxidase (MAO) activity is a peripheral marker of central serotonergic activity, and has been associated with aggressive, impulsive and hyperactive behaviour, alcohol and drug abuse. Central serotonergic activity has also been associated with plasma cholesterol levels. In the present longitudinal investigation in adolescents (n = 320) changes in platelet MAO activity and in plasma cholesterol levels over three years were measured, and their possible association with changes in aggressive and hyperactive behaviour, smoking, alcohol and drug use was studied. The measures were taken at age 15 and 18 years. Psychological data were obtained from teachers by using the Hyperactivity Scale [B. af Klinteberg, Studies on Sex-related Psychological and Biological Indicators of Psychosocial Vulnerability: A Developmental Perspective, University of Stockholm, Department of Psychology, 1988]. The results of the study show that in most of the tested individuals, platelet MAO activity is a relatively stable measure, however, there was a significant number of subjects with a noticeable change in MAO activity. In subjects with decreased platelet MAO activity, total and HDL cholesterol levels were significantly increased. Also, changes in HDL cholesterol and in platelet MAO activity were inversely associated with changes in the score of Concentration Difficulties. The changes in platelet MAO activity and cholesterol level were not associated with alcohol and drug use among the subjects. This longitudinal analysis provides preliminary evidence that changes in platelet MAO activity and cholesterol, which may reflect changes in central serotonergic activity are associated with attention deficit in adolescents.

Adolescent↗
PubMed1983

Monoamine oxidase inhibition and furazolidone-induced cardiomyopathy in turkey poults.

Furazolidone (FZ), a potent inhibitor of monoamine oxidase (MAO), fed at concentrations of 700 ppm to turkey poults 2 through 5 weeks of age, produces cardiomyopathy and cardiomegaly. To determine the role of MAO inhibition in FZ-induced cardiomyopathy, the effects of FZ were compared with those of a chemically different MAO inhibitor, tranylcypromine (TCP), and a chemically similar non-MAO inhibitor, nitrofurazone (NFZ). At 14 days of age, poults were divided randomly into four groups. Control poults were fed a standard turkey starter ration, and poults in the experimental groups were fed the standard ration that included one of the following drugs at the given concentrations: 700 ppm FZ, 350 ppm NFZ, or 50 ppm TCP. Activity of MAO was assayed in liver and kidney homogenates from poults chosen at random at 14, 17, 21, 28, and 35 days of age in one trial and on heart homogenates at 14, 15, 17, 19, and 28 days of age in another trial. Development of cardiomyopathy was assessed using an electrocardiographic (ECG) technique and substantiated with necropsy examination. Inhibition of MAO was observed only in the heart in FZ-fed poults, only in the kidney in NFZ-fed poults, and in all three tissues studied in TCP-fed poults. Under the conditions of this study, an increase in the incidence of cardiomyopathy, based on ECG data and necropsy results, occurred only in the FZ-fed group. The inability of the potent MAO inhibitor, TCP, to produce cardiomyopathy in this study supports the conclusion that the primary mechanism of FZ-induced cardiomyopathy in turkey poults is probably not due to MAO inhibition.

Animals↗
PubMed1996

Modulation of gene expression rather than monoamine oxidase inhibition: (-)-deprenyl-related compounds in controlling neurodegeneration.

(-)-Deprenyl has been used to irreversibly inhibit monoamine oxidase B (MAO-B) in Parkinson's disease (PD) and Alzheimer's disease (AD) as a possible means of improving dopaminergic neurotransmission or of reducing neuronal necrosis caused by oxidative radical damage. Recent research in tissue culture and animal models has shown that (-)-deprenyl can reduce neuronal apoptosis caused by a variety of agents, in a variety of neuronal subtypes through a mechanism(s) that does not require MAO-B inhibition. Studies using general P450 blockers have shown that one of the principal metabolites of (-)-deprenyl, (-)-desmethyldeprenyl, mediates the antiapoptotic action. Other research has shown that (-)-deprenyl can induce altered expression of a number of genes in preapoptotic neurons both in vitro and in vivo, including the genes for superoxide dismutase (SOD) 1 and 2, BCL-2 and BCL-XL, nitric oxide synthase, c-JUN, and nicotinamide adenine dinucleotide dehydrogenase. Antiapoptosis by (-)-deprenyl is associated with a prevention of a progressive reduction of mitochondrial membrane potential in preapoptotic neurons, which has been shown to occur early in apoptosis and is likely an initiating factor. The above changes in gene expression appear to reduce oxidative radical damage to mitochondria and maintain mitochondrial permeability, thereby blocking mitochondrial "signals" that initiate apoptosis. In situ evidence suggests that apoptosis contributes to neuronal death in a number of neurodegenerative diseases. If apoptosis is critical to the progression of one or more human neurodegenerative diseases, then transcriptionally active agents such as (-)-desmethyldeprenyl may be of value in treating the diseases. The kinetics of (-)-deprenyl metabolism, however, and its biodistribution after oral administration, make it unlikely that the antiapoptotic action has played a major role in benefits found for the drug in PD and AD to date.

Animals↗
PubMed1988

Different effects of monoamine oxidase inhibition on MPTP depletion of heart and brain catecholamines in mice.

Pargyline, an inhibitor of monoamine oxidase type B (MAO-B), did not prevent the depletion of heart norepinephrine 24 hr after a single dose of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) in mice. In mice killed 24 hr after the last of 4 daily doses of MPTP, the depletion of dopamine in the striatum and of norepinephrine in the frontal cortex was completely prevented by pargyline, but the depletion of heart norepinephrine was not prevented. These results with pargyline are the same as results obtained earlier with deprenyl, another selective inhibitor of MAO-B. The doses of pargyline and of deprenyl that were used resulted in almost complete inhibition of MAO-B activity (phenylethylamine as substrate) in brain, heart and liver of mice. Deprenyl did not inhibit MAO-A activity (serotonin as substrate) in brain, but pargyline caused some inhibition of MAO-A in brain. In heart and liver, serotonin was oxidized only at about 1/10 the rate of phenylethylamine oxidation, suggesting that MAO-B predominates in these tissues. Both pargyline and deprenyl caused some inhibition of serotonin deamination in heart and liver, suggesting that the oxidation may have been due partly to MAO-B. Experiments with selective MAO inhibitors in vitro showed that only about 20% of the oxidation of serotonin was occurring via MAO-B in heart and liver. The in vitro oxidation of MPTP by MAO in mouse brain, heart and liver was almost completely inhibited by pretreatment with either pargyline or deprenyl. Neither pargyline nor deprenyl had any significant effect on the concentrations of MPTP in brain or heart one-half hr after injection of MPTP into mice. The concentrations of the metabolite, MPP+ (1-methyl-4-phenyl-pyridinium), were markedly reduced in brain and in heart by pretreatment with either pargyline or deprenyl. The data suggest that MPP+ formation, which is necessary for the depletion of brain catecholamines after MPTP injection, may not be necessary for depletion of norepinephrine in heart. Since the oxidation of MPTP in vitro was inhibited more by pargyline or deprenyl pretreatment than was the appearance of MPP+ in vivo, the possibility exists that some MPP+ formation might occur by an enzyme other than MAO.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2005

Comparison of monoamine oxidase a in peripheral organs in nonsmokers and smokers.

UNLABELLED: Smokers have reduced levels of brain monoamine oxidase A (MAO A) leading to speculation that MAO A inhibition by tobacco smoke may underlie some of the neurophysiologic effects of smoking. Because smoking exposes peripheral organs as well as the brain to MAO A-inhibitory compounds, we determined whether smokers would also have reduced MAO A in peripheral organs. METHODS: We measured MAO A in peripheral organs in a group of 9 smokers and compared it with a group of nonsmokers studied previously. MAO A was measured using PET and serial scans with the MAO A-specific radiotracers (11)C-clorgyline and deuterium-substituted (11)C-clorgyline ((11)C-clorgyline-D2) using the deuterium isotope effect to assess binding specificity. The time course of radiotracer in the arterial plasma was also measured and data from the tissue time-activity curves and the arterial input function were analyzed using a 3-compartment model to estimate k(3), which represents the rate-limiting step for the irreversible binding of labeled clorgyline to MAO A. RESULTS: Tracer uptake at plateau was reduced with deuterium substitution for the heart, lungs, and kidneys, indicating specificity for MAO. There was no difference in organ uptake at plateau between nonsmokers and smokers though, for the smokers, the efflux of tracer from peak uptake to plateau was slower for the lungs. The area under the time-activity curve for the arterial plasma was also significantly reduced for smokers versus nonsmokers and the reduction occurred in the first few minutes after radiotracer injection. Smokers had an approximately 50% reduction in k(3) when compared with nonsmokers; however, k(3) did not differ for nonsmokers and smokers for the heart and the kidneys. CONCLUSION: Because MAO A breaks down serotonin, norepinephrine, dopamine, and tyramine, and because the lung is a major metabolic organ in degrading some of these substances, reduced lung MAO A may contribute to some of the physiologic effects of smoking. This study also revealed that the concentration of the radiotracers in the arterial plasma is significantly lower for the smoker versus the nonsmoker and that this appears to be caused in part by retention of the radiotracer in lungs. If this is generally true for other substances that are administered intravenously, then this needs to be considered as a variable that may contribute to different short-term behavioral responses to intravenously administered drugs for nonsmokers versus smokers.

Adult↗
PubMed1995

Pseudo-phaeochromocytoma after multiple drug interactions involving the selective monoamine oxidase inhibitor selegiline.

A patient presented with paroxysmal hypertension and typical clinical features of phaeochromocytoma, but with a normal adrenal computed tomographic scan and much higher plasma noradrenaline than adrenaline concentrations. Urinary vanillylmandelic acid concentrations were only moderately elevated. This syndrome probably arose as a consequence of an interaction between the monoamine oxidase inhibitor selegiline, the sympathomimetic agent ephedrine, and a tricyclic antidepressant. The mechanism of the interaction is thought to be related to increased sympathetic release of noradrenaline by ephedrine, inhibition of catabolism by selegiline, and inhibition of reuptake of noradrenaline by the tricyclic. Although newer selective monoamine oxidase inhibitors are considered to be safer than earlier non-selective inhibitors, they can also contribute to drug interactions mimicking phaeochromocytoma.

Bronchial Spasm↗
PubMed1984

Monoamine oxidase and semicarbazide-sensitive amine oxidase in spontaneously hypertensive and in normotensive control rats.

The aim of the present work was to compare monoamine oxidase (MAO) and semicarbazide sensitive amine oxidase (SSAO) activity in several tissues from spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY). Contribution of MAO-A, -B and SSAO to the metabolism of each substrate in each tissue was defined from experiments where the decrease of oxidative deamination of each substrate at a given concentration was measured as a function of increasing concentrations of a selective MAO-A, -B or SSAO inhibitor. In the heart, aorta and, to a lesser extent, the femoral arteries MAO-A activity was higher in SHR than in WKY. Similarly in the liver the enzyme activity was higher in SHR than in WKY but was due to the -B form of MAO. In all the other tissues studied (duodenum, brain, lungs, adrenals and kidneys) no difference in MAO-A, MAO-B or SSAO activity was found between SHR and WKY, except for the kidneys and brain, if the differences in the weights of these organs in SHR are taken into account.

Amine Oxidase (Copper-Containing)↗
PubMed1997

Effect of experimental diabetes on monoamine oxidase activity from discrete areas of rat brain: relationship with diabetes associated reproductive failure.

The effect of alloxan-induced diabetes was studied on the activity of monoamine oxidase (MAO), the oxidative deaminating enzyme of monoamine neurotransmitters. MAO was assayed from discrete brain regions like medial preoptic area and median eminence--arcuate region of hypothalamus, septum, amygdala, thalamus, hippocampus, pons and medulla. In all these areas studied, the induction of diabetes resulted in significant increase in MAO activity at 3, 8, 15 and 28 day intervals, whereas, the treatment of diabetic rats with insulin led to recovery in the enzyme activity. Blood glucose levels increased significantly after induction of diabetes and the recovery was seen after insulin treatment. These data suggest the involvement of MAO in diabetes associated alterations in physiological and endocrinological disorders.

Animals↗
PubMed1995

Intracranial microdialysis of salicylic acid to detect hydroxyl radical generation by monoamine oxidase inhibitor in the rat.

The effect of pargyline, a monoamine oxidase inhibitor, on the generation of hydroxyl free radicals (OH) was investigated using striatal microdialysis. Salicylic acid in Ringer's solution (0.5 nmol microliter-1 min-1) was infused through a microdialysis probe to detect the generation of hydroxyl radicals (OH) as reflected by the formation of dihydroxybenzoic acid (DHBA) in the striatum. When pargyline (100 nmol microliter-1 min-1) was infused in rat brain, the level of 3,4-dihydroxyphenylacetic acid (DOPAC) gradually decreased in a time-dependent manner. In addition, a marked elevation of DHBA was observed. The present results indicate that accumulation of dopamine (DA) in the extracellular fluid elicited by pargyline can be auto-oxidized, which in turn leads (possibly by an indirect mechanism) to the formation of cytotoxic OH free radicals.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1978

Distribution of monoamine oxidase in hippocampal region of the rat.

The distribution and development of type A and type B monoamine oxidase (MAO) activities in the hippocampal region of the rat was investigated with biochemical microdetermination. Type A MAO is absolutely dominant and unevenly distributed in the hippocampus. The development of type A MAO in the hippocampus seems to be delayed and reachs adult levels by the 30th day after birth.

Aging↗
PubMed1989

A colorimetric method for assay of serotonin deamination by monoamine oxidase.

The present method involves conversion of the aldehyde produced, as a result of serotonin deamination by monoamine oxidase, to its 2:4 dinitrophenyl hydrazone derivative which gives a stable, bright yellow colour in alkaline solution and can be measured colorimetrically. The derivative is however unstable in the acidic medium and has to be extracted into an organic solvent immediately. The details of the method and its standardization are discussed.

Animals↗
PubMed1976

Monoamine oxidase defect in essential arterial hypertension. A single dose pargyline test.

A defect in the level of monoamine oxidase activity of platelets was observed in essential arterial hypertension. This defect seems dependent upon a lower rate of synthesis of the enzyme and not to the presence of an isoenzyme, as the net rate of return of the enzymatic activity after pargyline inhibition does not significantly differ between hypertensive and normotensive subjects.

Adult↗
PubMed1985

A sensitive fluorometric assay for serum monoamine oxidase with kynuramine as substrate.

The detailed procedure of a new sensitive fluorometric assay for human serum monoamine oxidase (MAO) with kynuramine as substrate is described. The data on its reproducibility, stability, correlation with another method, and serum MAO levels for 150 healthy subjects and 205 patients with various diseases, are presented to support the usefulness of this method. Since our method is much simpler and more sensitive than other methods conventionally used, we can recommend it for routine clinical investigation.

Heart Failure↗