Genetics of platelet MAO activity in discordant schizophrenic and normal twins

Monoamine Oxidase B (MAO-B): A Target for Rational Drug Development in Schizophrenia Using PET Imaging as an Example

Monoamine oxidase B (MAO-B) is an important high-density enzyme involved in the generation of oxidative stress and central in the catabolism of dopamine, particularly in brain subcortical regions with putative implications in the pathophysiology of schizophrenia. In this chapter, we review postmortem studies, preclinical models, and peripheral and genetic studies implicating MAO-B in psychosis. A literature search in PubMed was conducted and 64 studies were found to be eligible for systematic review. We found that MAO-B could be identified as a potential target in schizophrenia. Evidence comes mostly from studies of peripheral markers, showing reduced platelet MAO-B activity in schizophrenia, together with preclinical results from MAO-B knock-out mice resulting in a hyperdopaminergic state and behavioral disinhibition. However, whether brain MAO-B is altered in vivo in patients with schizophrenia remains unknown. We therefore review methodological studies involving MAO-B positron emission tomography (PET) radioligands used to quantify MAO-B in vivo in the human brain. Given the limitations of currently available treatments for schizophrenia, elucidating whether MAO-B could be used as a target for risk stratification or clinical staging in schizophrenia could allow for a rational search for newer antipsychotics and the development of new treatments.

Up-regulation of ADM and SEPX1 in the lymphoblastoid cells of patients in monozygotic twins discordant for schizophrenia

The contribution of genetic factors to schizophrenia is well established and recent studies have indicated several strong candidate genes. However, the pathophysiology of schizophrenia has not been totally elucidated yet. To date, studies of monozygotic twins discordant for schizophrenia have provided insight into the pathophysiology of this illness; this type of study can exclude inter-individual variability and confounding factors such as effects of drugs. In this study we used DNA microarray analysis to examine the mRNA expression patterns in the lymphoblastoid (LB) cells derived from two pairs of monozygotic twins discordant for schizophrenia. From five independent replicates for each pair of twins, we selected five genes, which included adrenomedullin (ADM) and selenoprotein X1 (SEPX1), as significantly changed in both twins with schizophrenia. Interestingly, ADM was previously reported to be up-regulated in both the LB cells and plasma of schizophrenic patients, and SEPX1 was included in the list of genes up-regulated in the peripheral blood cells of schizophrenia patients by microarray analysis. Then, we performed a genetic association study of schizophrenia in the Japanese population and examined the copy number variations, but observed no association. These findings suggest the possible role of ADM and SEPX1 as biomarkers of schizophrenia. The results also support the usefulness of gene expression analysis in LB cells of monozygotic twins discordant for an illness.

Platelet monoamine oxidase activity as a biological marker in a Swedish forensic psychiatric population

Platelet monoamine oxidase (MAO) activities were determined in 58 non-psychotic males at forensic psychiatric examinations. The aim of the study was to investigate the role of platelet MAO activity as a biological marker in forensic psychiatry, a clinical field with growing need of safe predictors for both treatment outcome and behavior. The study population was heterogeneous with respect to clinical and personality disorders and personality traits. The results confirmed the role of platelet MAO activity as a biological marker for stable personality traits such as impulsiveness, monotony avoidance and aggressiveness. Disorders with high frequencies of these personality traits such as borderline personality disorder and type II alcoholism could secondarily be associated with low levels of platelet MAO activity, whereas no such associations could be found regarding other clinical or personality disorders. Neither psychopathy as assessed by the means of PCL-R nor behavior such as abuse or criminality could be associated with platelet MAO activity. The conclusion is that, due to its close relationship with stable personality traits, platelet MAO activity serves a marker for vulnerability also in forensic psychiatric populations. On the other hand it is not a marker for clinical or personality disorders, or behavior per se.

Monoamine oxidases and alcoholism. II. Studies in alcoholic families

Thirty-five alcoholic families have been studied to investigate the relationship between DNA markers at the monoamine oxidase (MAO) loci and 1) platelet activity levels and 2) alcoholism. A quantitative linkage analysis failed to reveal any evidence that the variation in activity levels cosegregates with the DNA markers. A sib-pair analysis did not reveal a significant excess of MAO haplotype sharing among alcoholic sibs, although the deviation from random sharing was in the direction consistent with an X-linked component. A reanalysis of platelet MAO activity levels in a subset of these families revealed that the lower levels previously found in alcoholics is more likely due to the differences between males and females. Only among males and only when a "broad" definition of alcoholism is used (and MAO activity levels are transformed to normality) does it appear that alcoholics have depressed activities compared to nonalcoholics. Finally, when the confounding due to gender difference is removed, no differences between type I and type II alcoholics are found in these families.

Evidence for a genetic association between alleles of monoamine oxidase A gene and bipolar affective disorder

We present evidence of a genetic association between bipolar disorder and alleles at 3 monoamine oxidase A (MAOA) markers, but not with alleles of a monoamine oxidase B (MAOB) polymorphism. The 3 MAOA markers, including one associated with low MAOA activity, show strong allelic association with each other but surprisingly not with MAOB. Our results are significant only for females, though the number of males in our sample is too small to draw any definite conclusions. Our data is consistent with recent reports of reduced MAOA activity in patients with abnormal behavioral phenotypes. The strength of the association is weak, but significant, which suggests that alleles at the MAOA locus contribute to susceptibility to bipolar disorder rather than being a major determinant.

Inhibition of monoamine oxidases by haloperidol and its metabolites: pharmacological implications for the chemotherapy of schizophrenia

The effect of haloperidol and its metabolites on human platelet monoamine oxidase B (MAO-B) and human placenta monoamine oxidase A (MAO-A) in vitro has been investigated. We found that 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-pyridinium (HP+), 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-1,2,3,6- tetrahydropyridine (HTP) and 4-chlorophenyl-1,2,3,6-tetrahydropyridine (CPTP) are potent inhibitors of MAO. HP+ appeared to be a reversible, uncompetitive and selective MAO-B inhibitor with a Ki of 0.83 microM. HTP was found to be an irreversible, uncompetitive and selective MAO-B inhibitor (Ki of 1.84 microM). CPTP inhibits both MAO-A and MAO-B. Some other haloperidol metabolites, i.e. 4-(4-chlorophenyl)-4-hydroxypyridine (CPHP), 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-1,2,3,6- tetrahydropyridine N-oxide (HTPNO) and reduced haloperidol (RHAL), do not inhibit MAO to any appreciable degree at concentrations up to 100 microM. The results suggest that haloperidol metabolites may contribute to the reduction of platelet MAO-B activity in schizophrenic patients undergoing neuroleptic chemotherapy. An examination of the literature reveals that schizophrenic patients with low platelet MAO activity exhibit a strong association with the use of haloperidol. Other possible pharmacological implications of the inhibition of MAO activity are discussed.

Idiopathic pain and depression

This report summarizes research on the hypothesis that idiopathic chronic pain syndromes and depressive disorders share certain common pathogenetic mechanisms. There is increasing evidence that this may be partly true. Not only do chronic pain syndromes respond to treatment with antidepressants, but there are also striking clinical similarities between these syndromes and depressive syndromes. However, important differences do exist (e.g., the courses of these disorders are usually dissimilar). Family studies show that affective disorders are common in first-degree relatives of patients with idiopathic pain syndromes, but it is impossible to conclude from this that clear-cut genetic factors are of importance. Factors common to both syndromes include common personality traits, shortened rapid eye movements in sleep EEG, hypercortisolaemia and pathological dexamethasone suppression tests, low levels of melatonin in serum and urine and high levels of endorphins and Fraction I in cerebro-spinal fluid. One important common pathogenetic mechanism seems to be disturbances in the serotoninergic system.

Pharmacological and clinical implications of MAO-B inhibitors

Although the involvement of monoamine oxidase B (MAO-B) in physiological function is not yet well understood, its inhibitors have been shown to be quite useful in the treatment of various neuropsychiatric disorders. Platelet MAO-B activity has been found to be reduced in several psychiatric disorders, related to substance abuse and associated with different personalities. 1-Deprenyl (selegiline), an archetypical MAO-B inhibitor, alone does not seem to exert an antidepressive effect, however, it may become useful when administered in combination with amine neurotransmitter precursors. MAO-B inhibitors are useful adjunct drugs to 1-DOPA in the symptomatic treatment of Parkinson's disease. Interestingly, 1-deprenyl alone can slow down the progress of otherwise disabled syndromes of Parkinson's disease. It has been proposed that 1-deprenyl may play a role in neuroprotection and neurorescue. MAO-B inhibitors can selectively and dramatically increase the level of beta-phenylethylamine, which has been shown to potentiate dopamine and noradrenaline function in the central nervous system. Several new types of highly selective, reversible and irreversible MAO-B inhibitors have recently been developed. The mechanism(s) of neuroprotective and rescue actions of 1-deprenyl and other MAO-B inhibitors will help to shed some light on our understanding of the neurodegenerative process.

Platelet monoamine oxidase activity in alcoholics, alcoholics with drug dependence, and cocaine addicts

The main objective of this investigation was to study the influence of drug dependence on platelet monoamine oxidase (MAO) activity in the presence and absence of alcoholism. One hundred and thirteen admissions to alcohol and drug treatment facilities participated in the study. Twenty-six met the criteria for alcoholism (group I), seventy-eight subjects were alcohol-/cocaine- and cannabis-dependent (group II), and the remaining nine were patients with DSM-III-R diagnosis of cocaine addiction (group III). MAO activity was assayed radiochemically with [14C]tyramine as a substrate (221 microM). The results of this study showed that platelet MAO activity [nmol of product formed x (mg protein)-1 x hr-1] (mean +/- SE) was significantly (p < 0.01) lower in all of these subjects (group I, 5.50 +/- 0.80; group II, 3.90 +/- 0.50; group III, 4.3 +/- 1.60) as compared with controls (14.85 +/- 1.13). Measurements of platelet MAO activity may provide us with a reliable biochemical marker for alcoholism and perhaps addiction to other substances of abuse (i.e., cocaine).

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.

Low platelet gamma-aminobutyrate aminotransferase and monoamine oxidase activities in chronic alcoholic patients

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO) were estimated in blood platelets from 25 male chronic alcoholics and from 27 healthy male volunteers without histories of alcohol abuse. Based on clinical criteria, the alcoholics were classified into type 1 or type 2 alcoholism. The activity of GABA-T was found to be lower both in type 1 and type 2 alcoholics than in healthy volunteers. With regard to MAO, the platelet activity was found to be significantly lower only in type 2 alcoholics in concordance with previous reports. No significant correlation was found between the activities of GABA-T and MAO in the blood platelets of healthy volunteers. The inhibitory effect of 400 mM ethanol on the platelet MAO activity increased with decreasing concentrations of the substrate phenylethylamine. The degree of inhibition of ethanol on the platelet MAO activity, however, did not differ significantly between alcoholics and controls.

Platelet monoamine oxidase in schizophrenia: a meta-analysis

We did a meta-analysis on all publications (English and other languages) concerned with platelet monoamine oxidase (MAO) in schizophrenia. Essentially, when patients were medicated with a neuroleptic, most studies found that schizophrenics had lower platelet MAO levels than controls. Administration of neuroleptic lowers MAO levels. MAO levels in drug-free schizophrenics were similar to controls. Only a minority of studies found drug-free schizophrenics had decreased platelet MAO levels.

Molecular properties of monoamine oxidases A and B

Monoamine oxidases A and B (MAO-A and B) catalyze the oxidative catabolism of biogenic amines and xenobiotics. Investigation of these mitochondrial membrane proteins shows that they differ in substrate preference, inhibitor specificity, tissue and neuronal cell distribution, immunological properties, and nucleotide and deduced amino acid sequences. Comparisons of MAO-A and B from the human, bovine, and rat species show strikingly high similarity (85-88%) in the amino acid sequences of each enzyme. Furthermore, three regions in MAO-A and B have sequence identities across species of 78, 88, and 86%. These regions correspond to a nucleotide-binding site near the N-terminal end that is found in the vast majority of enzymes that require flavin adenine dinucleotide (FAD), a region of unknown function, and the FAD-binding site toward the C-terminal end. Genomic clones of MAO-B which span almost the entire gene (greater than 40 kb) have been isolated, restriction mapped, and partially sequenced. Likewise, genomic clones of MAO-A that correspond to the 3'-flanking region have also been investigated. Current studies which focus on identification of the promoter and regulatory sequences should help to establish why MAO-A and B are localized in different subsets of neurons in brain.

Clinical characteristics of female alcoholics with low platelet monoamine oxidase activity

The aim of the present study was to see if female alcoholics had low platelet MAO activity and whether there was a correlation between low MAO activity in female alcoholics and specific clinical characteristics often observed in type II male alcoholics. In earlier studies, male alcoholics have been subdivided into type I and type II alcoholics. Type II alcoholics were characterized by early onset, a high frequency of depression and alcoholism in first degree relatives, a high frequency of drug abuse and social complications, sensation seeking behavior, extraversion, impulsive sensation seeking psychopathy, and low platelet MAO activity. In the present series it was demonstrated that the female alcoholics had significantly lower platelet MAO activities than the female healthy volunteers. The subgroup of female alcoholics with low platelet MAO activity, however, did not differ from female alcoholics with normal platelet MAO activity in the same way as male alcoholics with low platelet MAO activity have been shown to differ from male alcoholics with normal platelet activity. They did not have early onset, higher frequency of depression or alcoholism in their first degree relatives, nor more social complications than the female alcoholics with normal platelet MAO activity. Furthermore, they did not differ from the female alcoholics with normal platelet MAO activity in any personality trait covered by the Karolinska Scales of Personality (KSP).

Platelet MAO activity and the cortisol response to dexamethasone in major depression

Previous studies have sometimes found a positive relationship between platelet monoamine oxidase (MAO) activity and dexamethasone nonsuppression in depressed patients. To assess this relationship in more detail, we examined the association between these two biological variables in unmedicated depressed patients. A positive correlation between platelet MAO activity and 8:00 AM serum cortisol levels following an overnight dexamethasone test (1 mg) was observed. The relationship between high and low platelet MAO activity (median split) and suppression of serum cortisol levels was also significant. These relationships were stronger in bipolar patients. Multiple regression revealed that postdexamethasone 8:00 AM dexamethasone levels and platelet MAO activity were independent predictors of the 8:00 AM cortisol levels following dexamethasone. The possibility that platelet MAO activity may be a peripheral marker of brain serotonergic activity which in turn may affect various aspects of the hypothalamo-pituitary-adrenal axis activity, is discussed. We also found that all nine depressed patients studied greater than or equal to 15 days after admission were suppressors. Platelet MAO activity, but not 8:00 AM pre- or postdexamethasone serum cortisol, was related to the severity of depression.

Frontal midline theta activity and platelet MAO in human subjects

The distinctive theta rhythm that appears at the frontal midline during the performance of mental tasks has been designated as frontal midline theta (Fm theta). Fm theta shows individual differences and seems to be related to certain personality traits. In several studies, it has been indicated that low platelet monoamine oxidase (MAO) activity is also associated with certain personality traits. In the present study, we found a negative correlation between the appearance of Fm theta and platelet MAO activity. Subjects with marked extroversion show a high amount of Fm theta and low MAO activity. It is therefore suggested that Fm theta, an electrophysiological marker, may be useful in the investigation of monoamine functions in the central nervous system (CNS) by way of platelet MAO activity, a biochemical marker.

Platelet monoamine oxidase activity and schizophrenia--a myth that refuses to die?

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.

Platelet MAO in patients with idiopathic pain disorders

Patients with idiopathic pain syndromes have been compared to healthy volunteers and patients with neurogenic pain syndromes as concerns the activity of the enzyme monoamine oxidase (MAO) in thrombocytes. In both patients with idiopathic pain syndromes and in patients with neurogenic pain syndromes an increased frequency of patients with low platelet MAO activity was found. As low platelet MAO activity has been suggested to reflect low central serotoninergic activity the results are in line with findings of reduced concentrations of the serotonin metabolite 5-HIAA in CSF in patients with idiopathic pain syndromes. The results would also give some support for the suggestion that idiopathic pain syndromes might be a variant of depressive disease.

Personality traits and platelet MAO activity in alcohol and drug abusing teenage boys

The aim of this study has been to investigate whether teenage boys with mixed drug abuse differ from those with pure alcohol abuse as concerns personality traits and platelet monoamine oxidase activity. The series included 1129 consecutive 18-year-old males called to the Enlistment Center in the northern part of Sweden. A special inventory was constructed based on Zuckerman Sensation Seeking Scale (SSS), Eysenck's Personality Inventory (EPI), the Karolinska Scales of Personality (KSP) and questions about alcohol and drug consumption. The subjects with mixed drug abuse (n = 96) had high scores in the two subscales of SSS and KSP related to ability to stand boredom, high scores in both subscales of EPI and KSP related to impulsivity, high scores in Thrill and Adventure Seeking (TAS) and Experience Seeking (ES) of SSS as well as low platelet monoamine oxidase activity. The males with pure alcohol abuse (n = 33) also showed signs of monotony avoidance and impulsivity, but this type of abuse was not clearly related to low platelet monoamine oxidase activity and not to the aspects of curiosity included in the SSS such as TAS and ES. These findings are consistent with the picture earlier found as concerns "Type II" alcoholism which has an early onset, is genetically transmitted, is associated with mixed drug abuse and social complications.

Low platelet monoamine oxidase and sensation seeking in males: an established relationship?

A significant negative correlation between platelet monoamine oxidase (MAO) activity, a stable peripheral enzyme measure under genetic control, and sensation seeking, as measured using the Zuckerman Sensation Seeking Scale (SSS), has been reported for male subjects in several studies. As tobacco smoking has been related to both these measures, in the present study correlations were calculated among smoking and non-smoking male university students. Platelet MAO activity was negatively correlated with the Disinhibition and Total scales of the SSS. These correlations were not significantly different in smokers and non-smokers. The results are discussed in terms of recent evidence of reduced platelet MAO activity in psychiatric patients.

Factors associated with decreased platelet MAO activity in chronic schizophrenics

Platelet MAO activity was determined in a sample of chronic schizophrenics, including drug-free and neuroleptic-treated patients, and in a normal control group. Patients with MAO values below and above the median were compared with respect to several clinical, historical, neuroradiological and neuropsychological variables. The enzyme activity was significantly decreased in the whole patient group and in the subgroup of neuroleptic-treated patients, but not in the subgroup of drug-free patients. The only significant difference between low MAO and high MAO patients concerned drug status (higher percentage of patients on neuroleptics in the former subgroup). On stepwise discriminant function analysis, drug status (on neuroleptics vs. off neuroleptics) correctly classified 63.4% of patients.

Studies of biological factors associated with the inheritance of schizophrenia: a selective review

Although a familial component to schizophrenia has been established through several family, twin and adoption studies, an inherited biological factor has yet to be established. Efforts to define clinical familial subtypes of schizophrenia have generally been unsuccessful, although recent data from our study population of pairs of siblings with schizophrenia suggests that schizophrenia with recurrent episodes of major depression may define one such group. There have only been a few biological traits consistently found to be associated with schizophrenia and also found to be heritable. These findings (e.g. measures of monoamine metabolism, brain structural morphology, neurophysiological markers, and protein polymorphisms) are reviewed in the present chapter. The proportion of patients with any of the noted abnormalities never approaches 100%, nor have any been found to be specific to schizophrenia. Research into the biogenetics of schizophrenia is clearly just beginning.

Discrimination of idiopathic pain syndromes from neurogenic pain syndromes and healthy volunteers by means of clinical rating, personality traits, monoamine metabolites in CSF, serum cortisol, platelet MAO and urinary melatonin

The aim of the present study was to investigate the discriminative power of a series of variables (including determination of depressive symptomatology by means of a visual analogue scale, determination of personality traits by means of the Karolinska Scales of Personality, determination of monoamine metabolites in CSF, platelet MAO activities, serum cortisol before and after dexamethasone suppression and urinary melatonin) in differentiating chronic pain patients from healthy subjects, and patients with idiopathic pain syndromes from patients with neurogenic pain syndromes. Separately each of the measures gave a significant but often low contribution to the discrimination, while a combination of several measures gave a complete discrimination both between healthy subjects and patients with chronic pain syndromes and between patients with idiopathic and neurogenic pain syndromes, respectively.

Relationship between platelet MAO activity and concentrations of 5-HIAA and HVA in cerebrospinal fluid in chronic pain patients

Platelet monoamine oxidase (MAO) activity and concentrations of 5-HIAA and HVA in the cerebrospinal fluid (CSF) were estimated in a series of 54 chronic pain patients. Platelet MAO activity was found to correlate, positively to CSF concentrations of 5-HIAA and HVA, which had been adjusted in order to eliminate the influence of age and body height. However, only the correlation with 5-HIAA reached a significant level. When partial correlations were sought, only the positive correlation between platelet MAO activity and CSF 5-HIAA remained. The results support the notion that platelet MAO ia a biological marker for some trait dependent property of the central serotonergic system.

Platelet MAO concentration and molecular activity: II. Comparison of normal and schizophrenic populations

Platelet monoamine oxidase (MAO B) in 59 normal and 57 RDC-diagnosed medicated and unmedicated schizophrenic subjects was analyzed for whole platelet and extracted activities, specific concentration, and molecular activity. A novel radioimmunoassay using a monoclonal antibody elicited to human platelet MAO was used. Female schizophrenics showed no differences from female normals in MAO measures; however, these data could not be clearly evaluated because of confounding effects of age and drugs. Male schizophrenics treated with neuroleptics expressed significantly reduced whole platelet MAO activity, compared to untreated male patients. Compared with normal males, male schizophrenics showed significantly lowered molecular activities, along with elevated specific concentrations, which did not appear to be explained solely by drug usage. Additional mechanisms explaining the diminished molecular activity in male schizophrenics may be the presence of an endogenous irreversible inhibitor or a genetically determined, possibly structural, variant of MAO B.

Concentrations of monoamine metabolites in the cerebrospinal fluid of twins and unrelated individuals--a genetic study

The concentrations of the major monoamine metabolites, homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylethylene glycol (MOPEG), and 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF), of platelet monoamine oxidase (MAO) and of dopamine beta-hydroxylase (DBH)-activity in serum and CSF were determined in pairs of healthy mono- and dizygotic twins, brothers and unrelated individuals. Intraclass correlations were calculated for each category of pairs. Of the monoamine metabolites, only MOPEG was found to be under any major genetic influence. Genetic heritability for MOPEG was 0.74 with no evidence of cultural heritability or environment common to twins. For HVA and 5-HIAA, a familial influence was found, where the cultural heritability was higher than the genetic. As in previous studies of MAO in blood platelets and of DBH activity in serum, there was strong evidence for a genetic component. The genetic heritability for MAO was 0.78. For DBH in serum the genetic component was 0.98, and for DBH in CSF, 0.83. The demonstration of a familial influence on 5-HIAA and HVA in CSF requires a more detailed analysis of the character of such environmental and genetic influences, using more direct techniques.

Platelet monoamine oxidase activity and psychopathy

Platelet monoamine oxidase (MAO) activity appears to be correlated to certain diagnostic subgroups and symptom patterns. A group of criminal offenders hospitalized for forensic psychiatric assessment were studied. Male nurses and construction workers were used as controls. Patients who were diagnosed as psychopaths according to the criteria of Cleckley had significantly lower platelet MAO activity than the control group of construction workers.

Platelet MAO activity as a biological marker in subgroups of alcoholism

In the Stockholm Adoption Study, two types of alcoholism, "Type I" and "Type II", have been identified on the basis of genetic predisposition. In the present study, this classification has been applied to a clinical sample. The two types of alcoholism were clinically clearly identifiable. Type I alcoholism was characterized by late onset and few social complications. Type II alcoholism was characterized by early onset, use and abuse not only of alcohol, but also of glue, cannabis, amphetamine and opioids, together with several social complications. The subjects with Type II alcoholism had also more alcoholism and depression among their first-degree relatives than the subjects with Type I alcoholism. Furthermore, the two types of alcoholism were separable by means of the biological marker - platelet MAO activity. While platelet MAO activity was normal in Type I alcoholics, as compared with healthy controls, it was clearly low in the Type II alcoholics. This subclassification of alcoholism seems to be of value in future studies concerning the etiology, epidemiology and treatment of alcoholism.

Towards an aetiological classification of schizophrenia

The genetic contribution to schizophrenia is widely accepted, yet none of the proposed models of transmission has been convincing. Schizophrenia is generally viewed as aetiologically homogeneous with the exception of supposedly rare "phenocopies" associated with organic brain lesions and without a family history. However, up to one-third of schizophrenics have enlarged cerebral ventricles, and this appears to be a consequence of environmental damage. Although the aetiology of schizophrenia comprises genetic and environmental components acting in variable proportions, a simple division into familial and sporadic cases would facilitate research. Families with several ill members will be most valuable for molecular genetic studies, while the new brain imaging techniques should be particularly directed towards sporadic cases.

Platelet monoamine oxidase activity in schizophrenia: relationship to family history of the illness and neuroleptic treatment

Platelet monoamine oxidase (MAO) activity was determined in a large population of drug-free and haloperidol-treated schizophrenic patients and healthy controls and, in a second study, in a sample of schizophrenics after a wash-out period and at different times during treatment with haloperidol. Enzyme activity was significantly decreased in both acute and chronic haloperidol-treated schizophrenics, but not in drug-free schizophrenics, compared with normal controls. No significant difference was observed between drug-free schizophrenics with a family history of the illness and those without such history, and between healthy relatives of schizophrenic patients and normal controls without a family history of schizophrenia. MAO activity was significantly reduced after 14 and 21 days of haloperidol treatment, and such reduction did not correlate with response to treatment. These data strongly support the idea that neuroleptic intake may, at least in part, explain low MAO values repeatedly reported in schizophrenics.