Low platelet monoamine oxidase activity in pathological gambling

Decreased platelet monoamine oxidase (MAO) activity has been reported in association with sensation-seeking personality type and in some mental disorders associated with a lack of impulse control. Pathological gambling itself has been related with both sensation-seeking and reduced impulse control. Platelet MAO activity was investigated in 15 DSM-III-R pathological gamblers from our outpatient clinic. Gamblers had a significantly lower platelet MAO activity than a group of 25 healthy controls. The range of MAO levels in gamblers was also significantly shorter than in controls. In controls, platelet MAO levels showed the previously described negative correlations with sensation-seeking scores but not in gamblers. The findings are consistent with previous studies showing an association of low platelet MAO activity with impulse control disorders and raise some interesting therapeutic alternatives for pathological gambling.     

Low platelet monoamine oxidase activity in borderline personality disorder

Platelet monoamine oxidase (MAO) activity was significantly lower in nonpsychotic, nonorganic, unmedicated male inpatients with DSM-III-R borderline personality disorder (BPD) than in nonpsychiatric controls. Patients with BPD who also met DSM-III-R criteria for antisocial personality disorder had significantly lower MAO activity than those with BPD alone. Low MAO activity in this sample did not appear to be related to the comoroid presence of major depressive disorder or a history of substance abuse.     

Platelet monoamine oxidase B activity in Parkinson's disease: A re-evaluation

Summary An increase in platelet monoamine oxidase (MAO) B activity in drug-free parkinsonians (n=6) compared with healthy controls (n=10) has been confirmed using both phenylethylamine (PEA) and dopamine as substrates, reaching statistical, significance in the case of PEA oxidising activity (p<0.05). Thus, certain reports of raised platelet MAO B activity towards PEA but decreased activity towards dopamine in parkinsonians, raising the possibility of the existence of an abnormal form of MAO B in this condition, cannot be supported.     

Criminality and platelet monoamine oxidase activity in former juvenile delinquents as adults

Platelet monoamine oxidase (MAO) activity was estimated in 70 former delinquent boys and 40 controls now aged 38–46 years. Platelet MAO activity was compared with their early criminal behaviour (before the age of 15) and their late registered criminality from the age of 15). Mean platelet MAO activity in subjects with both early and late criminality was significantly lower than that in former delinquents without late criminality. There was no significant difference in mean platelet MAO activity between controls and delinquents with early but no late criminality. When delinquents with early criminality were divided into a low and a high MAO group, the relative risk to be registered for late criminality was about 3.1 times higher for the subjects in the low MAO group. Thus, individuals with low platelet MAO activity run an increased risk of continued criminal behaviour.     

Platelet monoamine oxidase activity: relation to genetic load of schizophrenia

Platelet monoamine oxidase (MAO) activity is significantly lower in chronic schizophrenic patients with a family history of schizophrenia compared to schizophrenics with no affected relatives and normal controls. These results are consistent with the concept of genetic and biologic heterogeneity in schizophrenia and suggest that the lack of uniformity across previous MAO studies of schizophrenia may be explained in part by the presence of biochemically normal phenocopies.     

Personality correlates of platelet monoamine oxidase activity and red cell lithium transport

Platelet monoamine oxidase (MAO) activity and the ratio of red cell to plasma lithium concentrations (Li ratio) may be important in the pathophysiology of, and genetic vulnerability to, some psychiatric disorders. By using the Clinical Analysis Questionnaire, we assessed personality correlates of MAO activity and the Li ratio in vitro in a sample of psychiatrically normal adult women. We found that there were correlates of each variable, and a unique constellation of personality traits when the two variables were considered simultaneously.     

Classification of patients with affective disorders using platelet monoamine oxidase activity,serum melatonin and post-dexamethasone Cortisol

Platelet monoamine oxidase activity (MAO), melatonin and Cortisol post-dexamethasone suppression test (DST) were examined in 28 patients with major affective disorder and in 20 controls. MAO activity was lower and Cortisol post-dexamethasone was higher in depressed patients. Platelet MAO activity and Cortisol in depressed and controls yielded high sensitivity (90%) and specificity (89%). The patients were re-examined after 10 years and categorized into affective psychosis or neurotic depression (ICD-9). Multidimensional analysis identified one subgroup coinciding in 92% with affective psychosis and another subgroup coinciding in 87% with neurotic depression. Combination of MAO, melatonin and post-DST Cortisol may be useful in the diagnosis of subgroups of depressed patients and in choice of therapy.     

Pentametric distribution of platelet monoamine oxidase activity

The distribution of catalytic activity of platelet monoamine oxidase (MAO) with both tryptamine and phenylethylamine as substrates was examined in 1,129 Swedish men at age 18 years. A mixture of five components was needed to describe the distribution, even when the original scale was transformed to remove skewness. The proportions of admixture were 2% for the extremely low component with a mean of -2.3 sigma, 29% for moderately low MAO (mean -0.8 sigma), 51% for intermediate MAO (mean 0.0 sigma), 15% for moderately high MAO (mean + 1.3 sigma), and 3% for extremely high MAO (mean + 3.0 sigma). Thus, the upper and lower deciles each contain contributions from two extreme components that differ from a much larger intermediate component with activity near the mean of the general population. This is compatible with a minimum of three alleles at a single major locus or with at least two polymorphic loci. The hypothesis that MAO activity is controlled by two alleles at a single locus was tested and rejected. The demonstration of at least five distinct components to the distribution of MAO warrants further research to characterize the biochemical structure and function of MAO enzyme variants as well as study of the behavioral correlates of the components.     

Low platelet monoamine oxidase activity: A possible biochemical correlate of borderline schizophrenia

Platelet monoamine oxidase (MAO) activity, psychiatric disorders, and family history of psychopathology were studied in 115 nonhospitalized, previously undiagnosed college student volunteers. Subjects were classified into two extreme groups: those with platelet MAO activity two standard deviations below the mean (“low-MAO” probands) and those with platelet MAO activity two standard deviations above the mean (“high”-MAO probands). Low-MAO probands were found to have a significant increase in the incidence of borderline schizophrenia and other psychiatric disorders compared to high-MAO probands. First-degree relatives of low-MAO probands were more often affected with psychiatric disorders and borderline schizophrenia than relatives of high-MAO probands. The data suggest that reduced platelet MAO activity is associated with psychiatric vulnerability and that the spectrum of schizophrenia may be more closely related to this vulnerability than other psychiatric disorders.     

Platelet phenolsulphotransferase activity,monoamine oxidase activity and peripheral-type benzodiazepine binding in demented patients

Summary Blood platelet phenolsulphotransferase and monoamine oxidase activities, as well as platelet peripheral-type benzodiazepine binding have been studied in several neuropsychiatric disorders, in order to identify biochemical markers for altered brain functioning. In the present work, we determined platelet phenolsulphotransferase and monoamine oxidase activities in demented patients: they showed significantly higher phenolsulphotransferase and monoamine oxidase activities than controls. A significant positive correlation was found between enzyme activities and severity of illness. In the same subjects, we evaluated platelet peripheral-type benzodiazepine binding: a significant reduction of B_max values was observed in demented patients, whereas K_d values did not substantially differ between the two subject groups.These findings are discussed with reference to central nervous system biochemical abnormalities of demented subjects: it may be that in Dementia of Alzheimer type either some central biochemical changes are reflected in certain peripheral tissues (such as platelets), or a systemic derangement occurs together with a cerebral involvement.     

Platelet monoamine oxidase activity in relation to alleles of dopamine D4 receptor and tyrosine hydroxylase genes

Human personality characteristics and vulnerability to psychopathology are to a large extent dependent upon genetic factors which have yet to be fully defined. The allele distribution of the dopamine D4 receptor (D4DR) and thrombocyte monoamine oxidase (trbc MAO) activity have both been associated with personality traits which are supposedly related, namely 'sensation seeking’according to Zuckerman and‘novelty seeking’according to Cloninger, respectively. In this report, the D4DR allele distribution and trbc MAO activity were studied in 31 psychiatric patients and 21 control subjects. Trbc MAO activity is a biochemical marker of personality that has been shown to be under strong genetic influence. However, no association between the D4DR alleles and trbc MAO could be observed in this material. To our knowledge, this is the first report comparing these two markers, and based upon the results obtained, we speculate that they may be connected with different types of overlapping personality characteristics. The allele distribution of the tyrosine hydroxylase (TH) gene was also determined. TH is the rate-limiting enzyme in the biosynthesis of catecholamines, and it is believed to be involved in different kinds of psychopathology. No covariation between TH gene alleles and trbc MAO activity or D4DR alleles was observed in this material.     

Blood platelet monoamine oxidase activity, serotonin uptake and release rates in anorexia and bulimia patients and in healthy controls

Platelet monoamine oxidase (MAO) activity, serotonin uptake rate and serotonin efflux rate have all been suggested to be markers for central serotonergic mechanisms. Platelet MAO activity is associated with certain personality traits, with low activity linked to traits such as impulsiveness, sensation-seeking and avoidance of monotony, all possible expressions of low central serotonergic activity. Low platelet serotonin uptake rate has been connected to unipolar depression and the rate of efflux, in the presence of the ATP uncoupler CCP, higher in bipolar depressives than in controls. Platelet MAO was found to be lower in 16 consecutive female inpatients fulfilling the DSM-III criteria for bulimia nervosa than in 12 female controls. Rates of serotonin uptake and efflux in the presence of CCP were, on the other hand, similar to the controls. In the controls there were no correlations between platelet MAO activity and any of the other parameters estimated. Vmax for the platelet uptake of serotonin correlated positively with the Km for the uptake, but not with any other parameter. The uninfluenced rate of efflux of serotonin correlated positively with the efflux in the presence of the ATP uncoupler CCP.     

Platelet monoamine oxidase and clinical phenomenology of schizophrenia

Platelet monoamine oxidase activity (MAO) was determined in 39 unmedicated chronic schizophrenic patients and 88 normal control subjects. Platelet MAO activity did not distinguish paranoid from nonparanoid patients or patients who met Taylor and Abrams criteria for narrowly defined schizophrenia from other schizophrenics. Enzyme activity was not related to either prognostic scores or age at onset of illness. MAO activity was decreased in patients compared to controls, and was lower in males than in females. Our findings indicate that clinical phenomenology, as defined in the present study, is of limited use in identifying biological subtypes of schizophrenia with deviant platelet MAO activity.     

Some kinetic parameters of platelet monoamine oxidase in chronic schizophrenia.

The michaelis constants (Vmax and Km) for platelet monoamine oxidase (MAO) with tyramine as substrate are found to be significantly lower in chronic schizophrenic patients than in normal controls. Furthermore, these kinetic parameters for the MAO of paranoid chronic schizophrenics are significantly lower than those for nonparanoid chronic schizophrenics. Paranoid chronic schizophrenia may be a separate biochemical disorder from other chronic schizophrenias.     

Platelet monoamine oxidase activity and schizophrenia —A myth that refuses to die?

Summary Platelet monoamine oxidase (MAO) activity was determined using kynuramine as a substrate in a group of schizophrenic patients (n =107), a group of healthy individuals (n =100), and a group of psychiatric patients who were neither schizophrenics nor alcoholics (n =110). No significant difference emerged between the schizophrenics and the other two groups, while a significant reduction in platelet MAO activity in a group of alcoholics (n = 60) was confirmed. Breaking down the schizophrenic group according to course of illness, phenomenology (paranoid-hallucinatory or not) and drug use did not lead to a significant deviation in platelet MAO activity in any of these subgroups. It can also be demonstrated from the literature that the results reached by most research teams question the usefulness of platelet MAO activity as a genetic marker for psychiatric illness.     

Neuroleptic drug effect on platelet monoamine oxidase and plasma amine oxidase in schizophrenia

Activity levels of platelet monoamine oxidase (MAO) and plasma amine oxidase (PAO) were determined in eight chronic schizophrenic patients who had been treated with neuroleptic drugs for 3 months. The mean reduction in platelet MAO activity was 18.6%. The extent of decrease was statistically significant. The reduction in enzyme activity was unrelated to serum iron levels. PAO activity was unaltered. The implications for schizophrenia research are discussed.     

A probable neuroleptic effect on platelet monoamine oxidase in chronic schizophrenic patients

Platelet monoamine oxidase activity (MAO) was studied serially over time in 16 chronic schizophrenic patients when medication free and then when medicated. Thirteen of the 16 patients had significant decreases in platelet MAO activity following neuroleptic drug treatment. The change in MAO activity was found to be correlated with response to treatment and to dose of medication.     

Platelet monoamine oxidase activity is related to MAOB intron 13 genotype

Summary. Monoamine oxidases (MAO) play a critical role in the degradation of endogenous and exogenous amines throughout the body. There are two distinct MAO isoforms, MAO-A and MAO-B, which both are encoded in genes on the X chromosome. Alterations in MAO-B activity have previously been connected with several neurological disorders. Platelet MAO (trbc-MAO) is exclusively of the B-type and the catalytic activity of this enzyme is under strong, yet unknown, genetic control. Specific trbc-MAO activity has been reported to be increased in certain neurodegenerative diseases and to correlate with personality traits such as sensation seeking and impulsiveness. In the present study, we investigated if trbc-MAO activity is associated with genotype at a variable region (A/G dimorphism) in intron 13 of the human gene encoding MAO-B. The MAOB intron 13 allele status and levels of trbc-MAO were determined for 55 Caucasian non-smoking males. Individuals with the "A-allele" displayed significantly lower enzyme activity than individuals with the "G-allele", i.e. 11.4 ± 0.6 nmol/10¹⁰ platelets/min compared with 13.5 ± 0.6 (mean ± SEM, p = 0.019). The present results suggest that the MAOB genotype may be involved in determining trbc-MAO activity. Received July 1, 1999; accepted January 11, 2000     

Increased platelet 3H-imipramine binding and monoamine oxidase B activity in Alzheimer's disease

Summary Several biochemical abnormalities in peripheral tissues have been reported in Alzheimer's disease (AD).With this in mind we studied platelet monoamine oxidase B (MAO B) activity and 3H-imipramine (IMI) binding in both AD patients and healthy subjects and found a significantly higher level of platelet MAO B activity and 3 H-IMI Bmax values in the AD patients. In view of the part that MAO B plays in metabolizing serotonin (5 HT) and of the relationship which exists between 3 H-IMI binding and 5 HT uptake, our results would suggest that with AD there occurs a complex dysfunction in the 5 HT system, at least at a peripheral level.     

Platelet monoamine oxidase activity in sensation seekers

Personality traits, as assessed by personality inventories, and platelet monoamine oxidase activities have been compared in the following two groups of normal subjects: (1) subjects who either have mountaineering as an active hobby or an interest in mountaineering and (2) subjects not interested in mountaineering. The group of subjects interested in mountaineering were found to be sensation seekers, as assessed by the Zuckerman Sensation Seeking Scale, and to have significantly lower platelet monoamine oxidase activities.