A study of selected catecholamine metabolizing enzymes: a comparison of depressive suicides and alcoholic suicides with controls

Rare CNVs in Suicide Attempt include Schizophrenia-Associated Loci and Neurodevelopmental Genes: A Pilot Genome-Wide and Family-Based Study

Suicidal behavior (SB) has a complex etiology involving genes and environment. One of the genetic components in SB could be copy number variations (CNVs), as CNVs are implicated in neurodevelopmental disorders. However, a recently published genome-wide and case-control study did not observe any significant role of CNVs in SB. Here we complemented these initial observations by instead using a family-based trio-sample that is robust to control biases, having severe suicide attempt (SA) in offspring as main outcome (n = 660 trios). We first tested for CNV associations on the genome-wide Illumina 1M SNP-array by using FBAT-CNV methodology, which allows for evaluating CNVs without reliance on CNV calling algorithms, analogous to a common SNP-based GWAS. We observed association of certain T-cell receptor markers, but this likely reflected inter-individual variation in somatic rearrangements rather than association with SA outcome. Next, we used the PennCNV software to call 385 putative rare (<1%) and large (>100 kb) CNVs, observed in n = 225 SA offspring. Nine SA offspring had rare CNV calls in a set of previously schizophrenia-associated loci, indicating the importance of such CNVs in certain SA subjects. Several additional, very large (>1MB) sized CNV calls in 15 other SA offspring also spanned pathogenic regions or other neural genes of interest. Overall, 45 SA had CNVs enriched for 65 medically relevant genes previously shown to be affected by CNVs, which were characterized by a neurodevelopmental biology. A neurodevelopmental implication was partly congruent with our previous SNP-based GWAS, but follow-up analysis here indicated that carriers of rare CNVs had a decreased burden of common SNP risk-alleles compared to non-carriers. In conclusion, while CNVs did not show genome-wide association by the FBAT-CNV methodology, our preliminary observations indicate rare pathogenic CNVs affecting neurodevelopmental functions in a subset of SA, who were distinct from SA having increased SNP risk-allele burden. These observations may open up new avenues in the genetic etiology of SB.

Parkinson's disease as a result of aging

It is generally considered that Parkinson's disease is induced by specific agents that degenerate a clearly defined population of dopaminergic neurons. Data commented in this review suggest that this assumption is not as clear as is often thought and that aging may be critical for Parkinson's disease. Neurons degenerating in Parkinson's disease also degenerate in normal aging, and the different agents involved in the etiology of this illness are also involved in aging. Senescence is a wider phenomenon affecting cells all over the body, whereas Parkinson's disease seems to be restricted to certain brain centers and cell populations. However, reviewed data suggest that Parkinson's disease may be a local expression of aging on cell populations which, by their characteristics (high number of synaptic terminals and mitochondria, unmyelinated axons, etc.), are highly vulnerable to the agents promoting aging. The development of new knowledge about Parkinson's disease could be accelerated if the research on aging and Parkinson's disease were planned together, and the perspective provided by gerontology gains relevance in this field.

Applying neuroimaging ligands to study major depressive disorder

The recent increase in radioligands available for neuroimaging major depressive disorder has led to advancements in our understanding of the pathophysiology of this illness and improved antidepressant development. Major depressive disorder can be defined as an illness of recurrent major depressive episodes of persistently low mood, dysregulated sleep, appetite and weight, anhedonia, cognitive impairment, and suicidality. The main target sites investigated with radioligand neuroimaging include receptor sites that regulate in response to lowered monoamine levels, targets related to removal of monoamines, uptake of ligands related to regional brain function, and target sites of antidepressants.

Advances in understanding the mechanisms and management of persistent pain in older adults

Older adults with persistent pain are not simply a chronologically older version of younger pain patients. Pain-related disability in older adults may be driven by pain 'homeostenosis', that is, diminished ability to effectively respond to the stress of persistent pain. Some of the comorbidities of ageing that can contribute to pain homeostenosis include cognitive and physical impairments, increased sensitivity to suprathreshold pain stimuli, medical and psychological comorbidities, altered pharmacokinetics and pharmacodynamics, and social isolation. A key distinction between older and younger individuals with persistent pain is the normal and pathological ageing-associated brain changes. These may alter the expression and experience of pain with impaired descending inhibition and dysfunction of pain gating mechanisms. Cognizance of these brain changes is needed to guide appropriate evaluation and treatment approaches. This paper reviews data that support these ageing-associated phenomena. Specifically, we discuss age-related changes in the brain (both normal and pathological) and in pain physiology; changes in experience and expression of pain that occur with dementia and contribute to pain homeostenosis; and unique aspects of age and pain-associated psychological function and their contribution to disability. We also present data demonstrating changes in brain morphology and neuropsychological performance that accompany persistent non-malignant pain in older adults and the treatment implications of these brain changes. Finally, preliminary data are presented on the efficacy of mindfulness meditation, a treatment that has been examined explicitly in older adults and targets optimizing brain function and descending inhibition.

Specific binding of [3H]Ro 19-6327 (lazabemide) to monoamine oxidase B is increased in frontal cortex of suicide victims after controlling for age at death

Previous studies have reported negative findings for the association among brain monoamine oxidase B (MAO-B) and suicidal behaviour. However those studies did not adequately control their main results for the influence of confounding variables such as age at death. We have evaluated the association of MAO-B density (assessed by [3H]Ro 19-6327 - lazabemide - binding) with type of death (suicide victims vs non-suicide controls) after controlling for age at death. Frontal cortex samples from 43 subjects (21 suicides, 22 controls) were assayed for MAO-B density at a single concentration of lazabemide (8 nM). A linear regression modelling approach comparing nested models resulted with both type of death (p<0.05) and age of death (p<0.01) as main explanatory variables for the variability of MAO-B density. Suicide victims had >30% more binding sites for lazabemide than controls. Contrary to previous reports, MAO-B density seems to increase in suicide victims.

A Review of Age Differences in the Neurophysiology of Nociception and the Perceptual Experience of Pain

OBJECTIVE

To better understand the nature of age differences in pain and nociception with the aging of the worlds' population.

METHODS

The evidence from numerous neurophysiologic and psychological studies suggest a small, but demonstrable age-related impairment in the early warning functions of pain. The increase in pain perception threshold and the widespread change in the structure and function of peripheral and CNS nociceptive pathways may place the older person at greater risk of injury. Moreover, the reduced efficacy of endogenous analgesic systems, a decreased tolerance of pain and the slower resolution of postinjury hyperalgesia may make it more difficult for the older adult to cope, once injury has occurred.

RESULTS

These age-related changes may be best conceptualized as a reduced capacity in the functional reserve of the pain system, at both ends of the intensity spectrum.

DISCUSSION

The clinical implications are obvious; older persons are likely to be especially vulnerable to the negative impacts of pain and pain associated events.

Ageing and the nigrostriatal dopaminergic system

BACKGROUND

Brain dopamine has been the focus of numerous studies owing to its crucial role in motor function and in neurological and psychiatric disease processes. Whilst early work relied on postmortem data, functional imaging has allowed a more sophisticated approach to the quantification of receptor density, affinity and functional capacity. This review aims to summarise changes in the nigrostriatal dopaminergic system which accompany normal ageing.

METHODS

A literature search focussed on postmortem and neuroimaging studies of normal ageing within the nigrostriatal dopaminergic tract. The functional significance of age-related effects was also considered.

RESULTS

There are significant reductions in pre- and post-synaptic markers of brain dopamine activity during normal ageing: However the rate of decline (linear or exponential), the effects of gender and heterogeneity and the mechanisms by which these changes occur remain undetermined. Limited data suggest there is a significant association between postsynaptic receptor density and specific aspects of motor and cognitive function.

CONCLUSION

The identification of strategies to improve dopaminergic transmission may delay the onset of motor and cognitive deficits associated with normal ageing. In order to develop effective preventative strategies, the causative mechanisms underlying age-related changes and the interaction between synaptic structure and function need to be more clearly elucidated.

Noradrenergic pathology in psychiatric disorders: postmortem studies

In this paper, we review research utilizing postmortem brain tissue in order to investigate the potential neuropathology of the noradrenergic system in psychiatric disorders. The postmortem tissue approach to the study of the noradrenergic system has been used primarily in investigations of the biology of suicide and depression. Findings from postmortem studies provide data generally consistent with the hypothesis that a norepinephrine deficiency exists in depression, and possibly in the victims of suicide. However, postmortem studies do not presently provide irrefutable evidence of noradrenergic neuropathology. Technical shortcomings, issues of reproducibility, and the strengths of postmortem research are reviewed. More rigorously performed postmortem research is needed to aid researchers in pinpointing specific neuropathologies associated with psychiatric disease.

Quantitative distribution of monoamine oxidase A in brainstem monoamine nuclei is normal in major depression

An abnormal expression of noradrenergic proteins (e.g., tyrosine hydroxylase, norepinephrine transporters) in the locus coeruleus has recently been demonstrated in subjects with major depression and/or victims of suicide. Monoamine oxidase A (MAO-A) is a key enzyme in the catabolism of biogenic amines and is expressed in brain noradrenergic neurons. In this study, the binding of [3H]Ro41-1049 to MAO-A was measured by quantitative autoradiography at multiple levels along the rostral-caudal axis of the noradrenergic locus coeruleus from subjects with major depression and age- and postmortem interval-matched control subjects who were psychiatrically normal. [3H]Ro41-1049 binding to MAO-A was unevenly distributed along the axis of the locus coeruleus, paralleling an uneven number of neuromelanin-containing (noradrenergic) neurons throughout the nucleus. Accordingly, there was a significant correlation between the number of neuromelanin-containing neurons per section and the specific binding of [3H]Ro41-1049 at any particular level of the locus coeruleus in control subjects (r(2)=0.25; p<0.001) and in subjects with major depression (r(2)=0.14; p<0. 001). Moderate levels of [3H]Ro41-1049 binding were observed in regions surrounding the locus coeruleus, including the central gray and the dorsal and median raphe nuclei. No significant differences in [3H]Ro41-1049 binding to MAO-A were observed at any level of the locus coeruleus, or raphe nuclei, comparing subjects with major depression to psychiatrically normal control subjects. These findings demonstrate that the pathophysiology of major depression is not likely to involve abnormalities in MAO-A.

Nigrostriatal monoamine oxidase A and B in aging squirrel monkeys and C57BL/6 mice

In this study we assessed the two forms of monoamine oxidase (MAO) in the caudate, putamen, and substantia nigra of young (4-year-old), intermediate-aged (11-year-old), and aged (20-year-old) squirrel monkeys and in the striata of young (2-month-old) and older (10-month-old) C57Bl/6 mice. MAO A and B activities were determined by measuring the rate of oxidation of the specific substrates phenethylamine and serotonin. In squirrel monkey, the vast majority of MAO activity was MAO B with activity of this isoform 10 times greater than of MAO A, while in mice the activity of the two forms was approximately equivalent. Although mice demonstrated nearly twofold selective increases in striatal MAO B between 2 and 10 months of age, neither MAO B nor A showed statistically significant changes with age in squirrel monkeys. These results document the marked differences between nonhuman primates and rodents with respect to the relative activities and the effects of age on MAO A and B, and indicate that increased MAO is not an inevitable feature of aging.

Brain GABA-transaminase and monoamine oxidase after chronic ethanol treatment in rats

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO-A and -B) were estimated in various brain regions of rats exposed to ethanol for 90 weeks. During the first period (weeks 1-58), the rats had access to both ethanol (10% w/v) and water during a 24-hr interval at the end of each week. At this point, the animals were given either a saline injection (intraperitoneally, group 1) or an ethanol injection (2.0 g/kg ip, group 2). During the second period (weeks 59-90), the rats in groups 1 and 2 had continuous access to both ethanol and water. The third group was composed of untreated control rats. Compared with controls, there was an increase of 20-45% in the mean brain GABA-T activity in both groups of ethanol-treated rats. However, analysis of the data for the individual ethanol-treated rats revealed a considerable difference in brain GABA-T activity. Thus, approximately 30% of the ethanol-treated rats showed approximately twice the activity of rats in the exposed groups and in the control group. There was no connection between ethanol intake, water intake, or body weight and GABA-T activity in any of the brain regions examined. There was no effect of ethanol in vitro on the activity of GABA-T in the brain cortex in concentrations of 20-100 mM, whereas acetaldehyde inhibited the activity by 15% at these concentrations. The present results suggest that there is a bimodal distribution with respect to the effect of ethanol on rat brain GABA-T activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency analysis of catecholamine axonal morphology in human brain. I. Effects of postmortem delay interval

The diverse morphologies of catecholamine axons in the human brain were examined by using tyrosine hydroxylase immunocytochemistry. Human brain tissue was obtained by either rapid autopsy (mean postmortem delay < 1 h) or routine autopsy (mean postmortem delay 5 h). Tissue blocks from the superior frontal cortex (Brodmann area 9), the hippocampal gyrus and the calcarine cortex (Brodmann area 17) were processed for tyrosine hydroxylase immunoreactivity. First, a quantitative method was developed to reliably identify differing morphologies of catecholamine axons in human brain tissue. A total of 625 tyrosine hydroxylase immunoreactive axons were randomly sampled from coded sections and classified into one of six distinct morphological categories. These categories were based upon axonal morphologies which were readily distinguished by trained observers, and moreover, further investigations demonstrated that entire tissue sections could be reliably re-sampled at intervals of up to six months. Second, regional variations in axonal distribution and the effects of increasing postmortem delay in tissue processing on the categories of tyrosine hydroxylase immunoreactive axon morphologies were examined. Postmortem delays of up to 6.5 hours were found to decrease the frequency of fine axons with varicosities (axon type 2) and increase thick-caliber straight axons (axon type 5) in all regions examined. The frequency of other morphological axon types did not change as a function of postmortem delay. In summary, the use of quantitative neuroanatomical measures of the catecholaminergic system in human brain tissue was found to be reliable and valid. It was furthermore demonstrated that postmortem delays affect selected morphological types of catecholamine axons.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoamine oxidase B in brains from patients with Alzheimer's disease: a biochemical and autoradiographical study

In vitro quantitative autoradiography using [3H]L-deprenyl, an irreversible and preferential inhibitor of monoamine oxidase B, was performed to investigate the localization of the enzyme in brains from senile dementia of Alzheimer type and control cases. Brains from three male patients with the clinical diagnosis of senile dementia of Alzheimer type and from three male control patients, without any known clinical history of neurological disorder, were obtained at autopsy. Cryosections of 100 microns thickness were mounted on gelatinized glass plates and dried over desiccant for one week at -20 degrees C. The sections were incubated with 10 nM [3H]L-deprenyl for 1 h and then exposed to film for four weeks. The autoradiographs were analysed by computer-assisted densitometry. Monoamine oxidase-B activities were also estimated in 1% homogenates from 10 different regions, using 10 microM beta-[ethyl-14C]phenylethylamine, in order to study the consonance between the autoradiographical and biochemical techniques. Both [3H]L-deprenyl binding and monoamine oxidase-B activities in senile dementia of Alzheimer type were higher than in the controls in all brain regions studied. The increase was highest in the white matter (about 70%) and in the order of 20-50% in the various gray matter regions. A high correlation coefficient (r approximately 0.9) was obtained between [3H]L-deprenyl binding and monoamine oxidase-B activity, both in the senile dementia of Alzheimer type and in the control brains.

Brain gamma-aminobutyrate transaminase and monoamine oxidase activities in suicide victims

The activity of gamma-aminobutyrate amino-transferase (GABA-T) and monoamine oxidase (MAO-A and -B) was measured in 42 postmortem human brains. Three brain regions (frontal cortex, cingulate cortex and hypothalamus) from 23 controls without known neurological or psychiatric disorder and from 19 suicide victims were analysed. The suicide victims were classified according to the use of violent and non-violent methods and to the presence or absence of a known history of depressive disorder. No difference was found between the series of suicide victims and the control subjects with regard to GABA-T activity. Carbon monoxide poisoning and death by drug overdose, however, were found to reduce the activity. The MAO-B activity did not differ between the groups. With MAO-A, however, a significant elevation (t = 2.01; P less than 0.05) was found in the hypothalamic region of the suicide victims. The difference seemed to be confined to the subgroup of suicides with a record of depressive disorder.

Striatal function in normal aging: implications for Parkinson's disease

Central to several current theories of the etiology of Parkinson's disease is the premise that the nigrostriatal dopaminergic system degenerates with normal aging. Much of the evidence for this assertion has come from postmortem neurochemical studies. We have used L-6-[18F] fluoro-Dopa and positron emission tomography in 26 healthy volunteers (age range, 27-76 years) to examine striatal and frontal cortical tracer uptake. Data have been analyzed by using a graphical approach to calculate an influx constant (Ki) for L-6-[18F]fluoro-Dopa uptake into the caudate, putamen, and medial frontal cortex of each subject. In the population studied, there was no decline in Ki with age for any of these structures. A series of physiological measurements made on the older subjects also showed few significant changes with age. The positron emission tomographic findings demonstrate preservation of nigrostriatal dopaminergic function in normal aging. The pathological process causing Parkinson's disease may operate closer to the time of presentation than has been suggested.

Serotonin concentrations and turnover in brains of depressed suicides

5-Hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations and 5-HT turnover (5-HIAA/5-HT) were determined in 6 brain regions from 19 suicide victims in whom a retrospective diagnosis of depression was established, and 19 age- and sex-matched control subjects. Thirteen of the suicides were free of psychoactive drugs at the time of death; 5 were receiving antidepressant drugs. 5-HT, 5-HIAA and 5-HT turnover did not differ significantly between the total, drug-free and antidepressant-treated suicides and controls in frontal and temporal cortex, caudate and hippocampus. 5-HIAA concentration was significantly higher in amygdala of drug-free suicides than controls, whereas 5-HT and 5-HT turnover did not differ. 5-HT concentration was significantly lower in putamen of the total and antidepressant-treated suicides and a similar reduction was also apparent in the drug-free suicides. 5-HT turnover in putamen was significantly higher in the total and drug-free suicides compared to controls. 5-HT and 5-HIAA concentrations in putamen were significantly lower in drug-free suicides who died by non-violent means than in those who died by violent means. Differences between controls and suicides could not be attributed to age, sex or postmortem delay. These results offer no support for the view that 5-HT turnover is reduced in depressed subjects who commit suicide.

Detection of 3,4-dihydroxyphenylglycolaldehyde in human brain by high-performance liquid chromatography

The monoamine oxidase A metabolite of noradrenaline, 3,4-dihydroxyphenylglycolaldehyde, is the precursor of 3,4-dihydroxymandelic acid, and 3,4-dihydroxyphenylglycol, metabolites of noradrenaline. Owing to difficulties in purifying this aldehyde, it has not been previously characterized or identified in biological sources. This paper describes an enzymatic synthesis, purification, and characterization of 3,4-dihydroxyphenylglycolaldehyde. The aldehyde metabolite is identified in postmortem human brain using high-performance liquid chromatography and electrochemical detection. We estimate the concentration in human hippocampus to be 0.164 +/- 0.05 nmol/g. The importance of this aldehyde metabolite of noradrenaline is discussed.

Catecholamine innervation of the human cerebral cortex as revealed by comparative immunohistochemistry of tyrosine hydroxylase and dopamine-beta-hydroxylase

The organization of the cortical monoamine systems, dopamine (DA), and noradrenaline (NA), which have been studied extensively in the rat and more recently in the monkey, had not yet been investigated directly in the human brain. We report here the first systematic account of the regional and laminar distributions of the catecholamine fibers in the human cerebral cortex, using immunohistochemistry of the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH), and dopamine-beta-hydroxylase (DBH) in 13 cytoarchitectonic areas (4, 6, 9, 3b, 5, 40, 17, 18, 23, 24, 29, insula, and hippocampus) sampled postmortem. The noradrenergic (NA) innervation, mapped with DBH-immunoreactivity (DBH-IR), displayed a characteristic density gradient in the neocortex (highest in the primary sensorimotor areas, decreasing rostrally and caudally) that contrasted with the more uniform density in the limbic cortices (24, 23, 29, insula, hippocampus). NA axons were present in all cortical layers and were least numerous in layer I. The DBH-IR fibers were only partly TH-immunostained (10-50%, on double-labeled sections), suggesting a heterogeneity of the cortical NA axons. The putative dopaminergic (DA) fibers were identified by comparing alternate or double-immunolabeled (DBH-TH) sections, as the TH-IR fibers which contain no DBH-IR. A DA-like innervation was present in all cortical areas, with major regional differences in density and laminar distribution, which closely paralleled cytoarchitectural buildups: 1) the DA-like innervation was densest in the agranular areas, primary and secondary motor areas, anterior cingulate, and insula; it distributed throughout layers I-VI; 2) density was lower in the granular cortices, areas 9 (prefrontal cortex), 23, 3b, 5, 40, and 18, displaying a bilaminar pattern in layers I and V-VI. In all areas, DA-like fibers were most abundant in the molecular layer, with a predominant distribution in its deepest part. Convoluted and coily fibers represented a unique morphologic aspect of the CA innervation in the human cortex. These findings are in agreement with findings in nonhuman primates and demonstrate major evolutionary changes in the organization of the cortical aminergic input as compared with rodents. The most striking features are the expansion of the DA innervation to the whole cortex and the peak of highest density in the motor areas. The regional differentiation of NA innervation is also accentuated. Slight differences were found in the laminar distributions of the amines in humans and primates. These data seem quite promising and open new research fields in neurologic and psychiatric diseases.

Stability of neuronal and glial marker enzymes in post-mortem rat brain

The enzymatic activities in post-mortem rat brain kept at 4 degrees C and at 25 degrees C were determined for a number of enzymes localized in specific cell types in the central nervous system. Choline acetyltransferase (CAT), glycerol-3-phosphate dehydrogenase (GPDH), glutamine synthetase (GS), lactate dehydrogenase (LDH) and 2',3'-cyclic nucleotide phosphohydrolase (CNPase) were found to be very stable at both 4 degrees C and 25 degrees C with only slight, if any, losses of activity being seen even at periods as long as 72 hr. Glutamic acid decarboxylase (GAD) activity was less stable than that of the other enzymes. In brains kept at 4 degrees C GAD activity was stable out to 24 hr after which it began to decline rapidly to 65% of control at 72 hr. In brains kept at 25 degrees C, GAD activity was stable for 6-8 hr and then began to steadily decline to 58% of control at 24 hr and 29% of control at 72 hr. Assuming that these enzymes have similar stabilities in post-mortem human brain, the effect of post-mortem delay in processing tissues may be of lesser significance than other factors with regard to the measured enzyme activities in human brain samples.

Catecholaminergic innervation of the septal area in man: immunocytochemical study using TH and DBH antibodies

The catecholaminergic innervation of the human septal area and closely related structures has been visualized by using tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) as immunocytochemical markers. TH-like immunoreactivity with no corresponding DBH labelling was considered to be indicative of dopaminergic fibers. Catecholaminergic innervation offered the following similarities to that of rodents: moderate innervation in the medial septal division, with predominant DBH immunolabelling; dense dopaminergic innervation in the lateral septal nuclei, organized in a laminar pattern; presence of dopaminergic pericellular arrangements in the dorsal septum and bed n. of the stria terminalis; clustering of dopaminergic terminals in n. accumbens associated with a medioventral zone of DBH-like immunoreactive fibers; close overlap between dopaminergic fields and acetylcholinesterase-reactive zones in both the lateral septum and the n. of the stria terminalis. Differences with the catecholaminergic septal innervation of rodents consisted of general caudal extension of the dopaminergic fields, possibly accounted for by the vertical stretching and caudal displacement of the septal nuclei in man; complementary lateromedial topography of dopaminergic and DBH-immunoreactive inputs in the n. of the stria terminalis as opposed to their dorsoventral organization in rodents; presence of TH-immunolabelled cell group in the anterior olfactory nucleus and parolfactory cortex, which seems specific for primates. Precise topographical mapping of the catecholaminergic structures in this central region of the limbic forebrain seems to be a prerequisite for accurate tissue sampling in the biochemical investigations of pathological cases and should help in the interpretation of aminergic dysfunction in a variety of human diseases.

Localization in rat brain of binding sites for parkinsonian toxin MPTP: similarities with [3H]pargyline binding to monoamine oxidase

A high-affinity binding site exists in rat brain for the parkinsonian toxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). The pharmacological specificity of this binding site suggests that it may correspond to monoamine oxidase (MAO). We have used quantitative autoradiography to map in detail the anatomical distribution of the [3H]MPTP binding site in rat brain and compared it with the anatomical distribution of MAO as determined by in vitro autoradiography with [3H]pargyline. Under the conditions of the assay, [3H]pargyline labeled the type B form of MAO. There were strong similarities in the anatomical distribution of [3H]MPTP and [3H]pargyline, with high levels of both binding sites occurring in the arcuate nucleus, the locus coeruleus, the dorsal raphe nucleus and all circumventricular organs. Low levels of both binding sites were found in the substantia nigra and the caudate-putamen. These results provide additional evidence that the high-affinity binding site for MPTP is MAO. The parkinsonian actions of MPTP might result from metabolites produced by MAO.

Increased synaptic markers in hippocampus of depressed patients

The neuronal adhesion molecule, D2-protein, and the marker for mature synapses, D3-protein, were studied by crossed immunoelectrophoresis in postmortem samples of human brain hippocampus and frontal cortex. The samples were obtained from 6 patients with endogenous depression, 6 patients with Parkinson's disease, and 9 controls without known neurological or psychiatric disorders. Both D2-protein and D3-protein were significantly increased in hippocampus of depressed patients compared to controls (32% and 30%, respectively) and compared to Parkinson's disease patients (31% and 24%, respectively). However, no significant change was observed in frontal cortex. Combined with the previously observed increase in the level of D2-like protein in blood plasma from depressed patients the findings may indicate that, at least in some regions of the brain, synaptic turnover is increased during depression.

Brain and liver monoamine oxidase type A and type B activity in alcoholics and controls

Monoamine oxidase activity in human postmortem brain and liver samples was measured in a group of patients with a prior history of alcoholism and compared to a control group with no prior history of alcoholism. Liver samples from patients with a prior history of alcoholism showed significantly lower monoamine oxidase activity with both phenylethylamine and serotonin as substrates. Postmortem brain samples, however, were not different in the two groups.

Platelet and fibroblast monoamine oxidase in alcoholism

Monoamine oxidase (MAO) activity has been reported to be low in platelets (MAO B) and brain (MAO A and B) of some patients with alcoholism compared to control subjects. Whether the decreased platelet MAO activity found in alcoholism is secondary to the effect of alcohol or exists before alcohol abuse is not clear. The hypothesis that altered MAO A activity is determined by an abnormality in the genetic regulation of the enzyme can be tested by measuring MAO A activity in human fibroblasts cultured under controlled conditions. We first studied the kinetic parameters of platelet MAO B activity in patients hospitalized for treatment of alcoholism. Vmax was 38% lower in the patients (n = 14) than in normal controls (n = 22), but the enzyme affinity (Km) for the substrate tyramine was unchanged. Patients with the five lowest levels of platelet MAO activity had MAO activity measured from fibroblasts cultured from skin punch biopsies. Their fibroblast MAO activity was within the normal range, showing a dissociation between platelet MAO B and fibroblast MAO A activities and suggesting that MAO A activity is not low for genetic reasons in alcoholic subjects who do have low platelet MAO B activity.

Changes of biogenic amines and their metabolites in postmortem brains from patients with Alzheimer-type dementia

Noradrenaline (NA), 3,4-dihydroxyphenylethylamine (dopamine, DA), 5-hydroxytryptamine (serotonin, 5-HT), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were measured in 22 regions of postmortem brains from four histologically verified cases with Alzheimer-type dementia (ATD) and nine histologically normal controls. Compared with the controls, concentrations of 5-HT and 5-HIAA in the ATD brains were significantly reduced in nine regions (superior frontal gyrus, insula, cingulate gyrus, amygdala, putamen, medial and lateral segments of globus pallidus, substantia nigra, lateral nucleus of thalamus) and in eight regions (amygdala, substantia innominata, caudate, putamen, medial and lateral segments of globus pallidus, medial and lateral nuclei of thalamus), respectively. NA concentrations of the ATD brains were significantly reduced in six regions (cingulate gyrus, substantia innominata, putamen, hypothalamus, medial nucleus of thalamus, raphe area). In contrast, significant reductions of DA and HVA concentrations in the ATD brains were found only in putamen and amygdala, respectively. The 5-HIAA/5-HT ratio in the ATD brains decreased significantly in locus coeruleus, while the HVA/DA ratio increased significantly in putamen and medial segment of globus pallidus. These findings suggest that the serotonergic and noradrenergic systems are affected, while the dopaminergic system is relatively unaffected in ATD brains.

Characterization of membrane-bound and soluble catechol-O-methyltransferase from human frontal cortex

Catechol-O-methyltransferase (COMT; E.C. 2.1.1.6) from human frontal cortex occurs in both a soluble and membrane-bound form. Attempts to solubilize the membrane-bound transferase by repeated washing or by extraction into solutions of high ionic strength were unsuccessful. The finding that Triton X-100 was capable of solubilizing membrane-bound COMT suggested that the membrane-bound transferase is an integral membrane protein. The membrane-bound and soluble enzymes did not differ in their requirements for magnesium ions or in their pH-activity profiles; both enzymes showed an optimum near pH 8.0 when assayed in phosphate buffer. In addition, the two enzymes did not differ in the degree of inhibition caused by CaCl2, both enzymes displaying 65% inhibition at 2.5 mM CaCl2. The competitive inhibitors tropolone and nordihydroguaiaretic acid displayed Ki values for the membrane-bound transferase five- to 10-fold lower than those observed for the soluble transferase. Solubilization of membrane-bound COMT in Triton X-100 resulted in an increase in the apparent Km value of the membrane-bound transferase for dopamine. The increase in Km appeared to be due to apparent competitive inhibition by Triton X-100 and reached a limiting value of approximately 80 microM. These results confirm that membrane-bound COMT is an integral membrane protein that may be structurally distinct from soluble COMT.

Postmortem monoamine oxidase enzyme kinetics in the frontal cortex of suicide victims and controls

Serotonin, a preferred monoamine oxidase (MAO) A substrate may be deficient centrally in suicide victims. In postmortem samples of frontal cortex from suicide victims we demonstrated receptor changes in the serotonergic system supportive of this hypothesis. These changes were not accompanied in this series of brain samples by alterations in either MAO A or B enzyme kinetics. Thus brain MAO A is not a useful indicator of altered serotonergic function in suicide victims. We did confirm an age-related increase in cortical MAO B but not MAO A enzyme concentrations in both controls and suicide victims.

Dopamine and depression: a review of recent evidence. I. Empirical studies

This paper reviews evidence from human, predominantly clinical, studies, relevant to the hypothesis that depression involves reduced levels of dopamine (DA) function. With the exception of Parkinson's disease, there is little evidence that treatments which decrease DA function are potent inducers of depression, but it is argued that such a relationship might not necessarily be expected. There is good evidence that the nigro-striatal DA system is underactive in retarded depressions, and some evidence that DA agonists are therapeutically effective in these cases. It remains unclear whether changes in DA function are primary or secondary.

Monoamine levels and monoamine oxidase activity in different regions of rat brain as a function of age

The levels of norepinephrine, dopamine, 5-hydroxytryptamine and the activity of monoamine oxidase were estimated in cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum and midbrain of 21-day-old, 3-, 6-, 12- and 24-month-old male albino rats of Wistar strain. No significant change with age was found in the levels of all the three amines in cerebral cortex and cerebellum, while medulla oblongata showed a significant decrease of all the amines by 24 months of age. Hypothalamic norepinephrine, dopamine and striatal dopamine showed a highly significant decrease by 24 months of age, whereas 5-hydroxytryptamine in hypothalamus, norepinephrine and 5-hydroxytryptamine in striatum and dopamine in midbrain did not show any appreciable change with age. Monoamine oxidase activity in all the regions except cerebellum showed a significant increase by 24 months of age compared to 3- and 6-month-old rats.

The locus coeruleus and its possible role in ageing and degenerative disease of the human central nervous system

The central noradrenergic pathways with the mammalian brain are principally based on that group of nerve cells within the reticular substance of the upper pons known as the locus coeruleus. The physiological role of these nerve cells appears to be one of maintaining homeostasis within the central nervous system, whatever adverse conditions prevail in the rest of the body, through governing the flow of blood through, and degree of water permeability of, the capillary bed. The extensive ramifications of these noradrenergic terminals mean that the atrophy and loss of nerve cells from locus coeruleus that occurs in old age, and especially so in degenerative diseases of the central nervous system such as Alzheimer's disease and other conditions, will have widespread repercussions for brain function. The chain of physiological disturbances set up as a result of this cell loss may mean a progressive failure of homeostasis within the brain, which in the extreme may culminate in that pattern of mental breakdown which is usually termed dementia.

Relative postmortem stability of spinal motoneuronal proteins detectable by two-dimensional electrophoresis

The suitability of using spinal tissue several hours after death for analysis by high resolution two-dimensional electrophoresis has been examined. It was found that many of the proteins of bovine spinal motoneurons detectable on two-dimensional polyacrylamide gels appear to be relatively stable in situ at room temperature during the first postmortem day. When extracts of total proteins from ventral roots and motoneuronal cell bodies isolated from 1-d-old tissue were examined, all spots could be matched to control gels. Upon visual inspection of the gels, postmortem changes in the amount of stain associated with a spot were obvious in three of 364 proteins from isolated motoneuronal cell bodies and none of 237 proteins from ventral roots. Other proteins underwent quantitative changes that were detected only after computer-assisted densitometry on the gels, whereas some did not appear to change at all. In the neuropil surrounding the motoneuron cell bodies, more pronounced changes in protein patterns occurred during the postmortem period. We conclude that properly controlled two-dimensional electrophoretic analyses of postmortem spinal tissue can provide reliable qualitative and quantitative information about the antemortem protein composition of spinal motoneurons.

Contribution of sulfate conjugation, deamination, and O-methylation to metabolism of dopamine and norepinephrine in human brain

The kinetic constants were determined for dopamine (CA) and norepinephrine (NE) metabolism by phenolsulfotransferase (PST), type A and B monoamine oxidase (MAO), and membrane-bound and soluble catechol-O-methyltransferase (COMT) in frontal lobe preparations of human brain. PST and membrane-bound COMT were found to have the lowest Km values for both catecholamines. By means of the appropriate rate equations and the calculated kinetic constants for each enzyme, the activity of each enzymatic pathway was determined at varying concentrations of DA and NE. Results indicate that deamination by MAO is the principal pathway for the enzymatic inactivation of DA whereas NE is largely metabolized by MAO type A and membrane-bound COMT under the in vitro assay conditions used. At concentrations less than 100 microM, soluble COMT contributes less than 5% to the total catabolism of either catecholamine. PST can contribute up to 15% of the total DA metabolism and 7% of NE metabolism.

Increased platelet monoamine oxidase activity in affective disorders

Platelet monoamine oxidase activity was determined in 52 unipolar depressive patients, 26 patients with bipolar affective disorder and 48 controls using phenylethylamine as substrate. Unipolar depressive patients of either sex and bipolar depressive women showed significantly higher platelet MAO activity than controls. Women had higher activity than men. Neither age nor serum lithium level correlated with enzyme activity and there was no significant change in activity after the institution of lithium treatment.

Age effect on dopamine and serotonin metabolite levels in cerebrospinal fluid

Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) were measured in lumbar cerebrospinal fluid from a group of patients ranging in age from 1 week to 45 years. Quantitation of these biogenic amine metabolites was achieved using a gas chromatographic/mass spectrometric technique. The subjects had various specific disorders of the nervous system, though patients with movement disorders and biochemical defects known to affect the neurotransmitter systems examined in this study were specifically avoided. The results indicated a strong inverse correlation in children between CSF HVA and 5-HIAA concentrations and age. The decline in these metabolites with age appeared to be exponential. No significant age effect was observed for MHPG. The results indicate the importance of comparing CSF metabolite levels in children with values in age-matched controls.

Enzyme alterations in brain tissue during the early postmortal interval with reference to the histomorphology: review of the literature

The state of research on enzyme alterations in brain tissue during the early postmortal interval is surveyed with special reference to the histomorphology; the questions currently discussed in the literature are given special consideration. The type of alterations appearing during the postmortal interval and their dependency on the length of the interval are described so that practically applicable conclusions may be drawn. The findings on enzyme alterations presented in the literature (enzymes of the oxidative metabolism, transmitter, enzymes) are compiled in tables. It could be shown that important structural alterations ascertainable with light microscopy and quantitative alterations in enzyme activity ascertainable with biochemical methods do not usually occur during a 6- to 8-h postmortal interval. Qualitative investigations (i.e., histoenzymatic studies) with longer postmortal intervals and with positive findings are applicable.

Titration of human brain monoamine oxidase -A and -B by clorgyline and L-deprenil

The interaction of clorgyline and L-deprenil with the -A and -B forms of human brain monoamine oxidase (MAO) has been studied. Both compounds inhibit cerebrocortical MAO in a manner consistent with a 'suicide' inactivation of the enzyme. The interaction of clorgyline with the -A form of the enzyme appears to take place almost entirely at specific binding sites, and the conditions required for this inhibitor to 'titrate' the concentrations of MAO-A have been elucidated. L-Deprenil has also been used to titrate the concentration of the -B form of MAO in cerebrocortical homogenates, but there is a considerable degree of non-specific binding of this compound. The two inhibitors have been used to titrate the concentrations of the two enzyme forms in frontal cortex homogenates from different age groups. There was a significantly higher MAO-B activity for the age range 73--95 years than for the age range 2--63 years. No significant differences between the two age groups were found for MAO-A. The activity of MAO-A in the samples correlated very well with the concentration of this enzyme form. Titration of the B-form of the enzyme with L-deprenil indicated an increased enzyme concentration with age, although other factors, such as the non-specific binding of this compound, could contribute to this effect.

The effect of age on the activity and molecular properties of human brain monoamine oxidase

The effect of age upon monoamine oxidase -A and -B (MAO-A and -B) in 23 different, regions of human brain was determined. There was a significant positive correlation with age in 19 out of 23 regions for MAO-B, but no positive correlation with age was found for MAO-A. The increased MAO-B activity was found, in 5 out of 5 regions tested, to be due entirely to an increased enzyme concentration, rather than due to an increased molecular turnover number of the enzyme. The responses of the mitochondrial marker enzymes succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) were studied in 5 brain regions, and no consistent change in activity found with age. The lysosomal enzyme acid phosphatase was found to tend towards an increased activity with age. No difference in either the specific activities or molecular characteristics of MAO were found between men and women. Cross-correlation studies of the data, after compensation for the effects of age, indicated that the activities of the two enzyme forms are under some form of organized control across the whole brain. Such a finding is consistent with a genetic regulation of the enzyme forms.

Choline acetyltransferase and acetylcholinesterase abnormalities in senile dementia: importance of biochemical measurements in human post-mortem brain specimens

Choline acetyltransferase and acetylcholinesterase have been assessed in human aging brains, in demented and agonal states. Choline acetyl transferase decreased during aging in normal brain when measured in the cerebral cortex. Choline acetyltransferase was also reduced in several other brain areas in patients with Alzheimer's disease and in one patient with Creutzfeldt-Jakob disease. Choline acetyltransferase was also reduced in bronchopneumonia and in some terminal conditions. On the contrary, the activity was not reduced in patients who died after cerebrovascular accidents. Acetylcholine esterase, although it followed the general trend of choline acetyltransferase, did not yield significant results.

The activities of brain dopamine-beta-hydroxylase and catechol-O-methyl transferase in schizophrenics and controls

It has been suggested that deterioration of central noradrenergic pathways may be responsible for the production of certain schizophrenic symptoms, and that such a degeneration might be reflected in lowered dopamine-beta-hydroxylase (DBH) activity in the brains of schizophrenics. The present study revealed that in rats lowered DBH activity was a sensitive index of noradrenergic degeneration. In the postmortem brains of 12 controls and 12 schizophrenics, however, no significant difference in DBH activity between controls and schizophrenics was found. DBH activity was relatively unstable postmortem and adversely affected by neuroleptic drugs, and these factors may have contributed to the previous finding of lowered DBH activity in the brains of schizophrenics. The activity of catechol-O-methyl transferase, which has also been previously reported as low in the brains of schizophrenics, was found to be no different in the controls of the present study.