Pathology of cortical development and neuropsychiatric disorders

Epilepsy is a well-documented consequence of about 150 rare genetic syndromes and malformations of the central nervous system. These syndromes are generally associated with fairly gross defects within the central nervous system and they were thought to be responsible for a small minority of cases. However, improved methods of neuropathological investigations and extensive magnetic resonance imaging studies have revealed a range of disturbances in cortical cytoarchitecture in patients with epileptic seizures previously considered as idiopathic (up to 70% of epilepsy). Structural abnormalities have also been demonstrated in the brain in schizophrenia. These consist of disturbed cortical cytoarchitecture (best described in the temporal lobe) and a diffuse loss of grey matter. The absence of the pathological stigma characteristic of degenerative processes indicates that these structural changes are the result of an abnormal pattern of brain development. The relationship between the type and location of developmental abnormality and the subsequent clinical syndrome (e.g. generalized or localized epilepsy) and the effects of aberrant cortical development on the functional integrity of the adult brain require definition.

Overexpression of s100beta in Down's syndrome: correlation with patient age and with beta-amyloid deposition

S100beta is an astrocyte-derived uritotrophic' cytokine which has been implicated in the pathogenesis of Alzheimer's disease. S100beta overexpression by plaque-associated astrocytes correlates with growth of abnormal (strophic') neurites in beta-amyloid plaques, one of the major neuropathological hallmarks of Alzheimer's disease. As the characteristic neuropathological changes of Alzheimer's disease are virtually universal in middle-aged Down's syndrome patients, studies of Down's syndrome patients provide a unique opportunity to investigate the pathophysiological processes underlying the development of Alzheimer-type neuropathological changes. Computerized morphometric analysis was used to quantify astrocyte activation and astrocytic expression of S100beta, and to correlate these with beta-amyloid deposition, in a clinically well-characterized cohort of Down's syndrome subjects, aged 13-65 years. There were significant positive correlations between S100beta expression and patient age, and between S100beta expression and cerebral cortical beta-amyloid deposition. Moreover, the numbers of activated (enlarged) astrocytes overexpressing S100beta showed a significant correlation with the numeric density of beta-amyloid plaques, from the youngest to the oldest ages and within age ranges where pathology is most florid, while no such relationship was found between the numbers of small, non-activated S100beta-immunoreactive cells and numerical density of beta-amyloid plaques. These correlations, together with established functions of S100beta, are consistent with the idea that S100beta overexpression promotes beta-amyloid plaque formation and progression in Down's syndrome.

A comparison of manual and semi-automated methods in the assessment of axonal injury

Diffuse axonal injury (DAI) in the central nervous system is a common cause of post-traumatic coma and may result in varying degrees of disability up to and including the vegetative state. Experimental studies in man and animals have previously relied upon semi-quantitative grading systems for determining the relationship between the extent of DAI and the clinical features of patients. Using beta-amyloid precursor protein immunocytochemistry for the detection of DAI in sections of corpus callosum from 15 cases of fatal head injury, we have developed a quantitative image analysis technique for the assessment of axonal injury. This new method is objective and reproducible and should allow better correlation with biomechanical, radiological, and clinical parameters to increase our understanding of DAI.

Is there a genetic basis for the deposition of beta-amyloid after fatal head injury?

1. Alzheimer's disease is a heterogeneous disorder that may be caused by genetic or environmental factors or by a combination of both. Abnormalities in chromosomes 1, 14, and 21 have all been implicated in the pathogenesis of the early-onset form of the disease, while the epsilon 4 allele of the apolipoprotein E gene (on chromosome 19) is now recognized as a risk factor for early- and late-onset sporadic and familial Alzheimer's disease. 2. The best-established environmental trigger for the disease is a head injury, based on epidemiological and neuropathological evidence. Approximately 30% of patients who die after a single episode of severe head injury show intracerebral deposition of beta-amyloid protein (A beta), a protein that is thought to be central to the pathogenesis of Alzheimer's disease. 3. Recent studies have revealed an over-representation of the apoE epsilon 4 allele in those head-injured patients displaying A beta pathology, thus providing the first evidence for a link between a genetic susceptibility (apoE epsilon 4) and an environmental trigger (head injury) in the development of Alzheimer-type pathology.

Distribution of interleukin-1-immunoreactive microglia in cerebral cortical layers: implications for neuritic plaque formation in Alzheimer's disease

Activated microglia overexpressing interleukin-1 (IL-1) are prominent neuropathological features of Alzheimer's disease. We used computerized image analysis to determine the number of IL-1 alpha-immunoreactive (IL-1 alpha +) microglia in cytoarchitectonic layers of parahippocampal gyrus (Brodmann's area 28) of Alzheimer and control patients. For cortical layers I and II, the numbers of IL-1 alpha + microglia were similar in Alzheimer and control patients. For layers III-VI, the numbers of IL-1 alpha + microglia were higher than that seen in layers I-II for both Alzheimer and control patients. Moreover, for layers III-VI, the number of IL-1 alpha + microglia in Alzheimer patients was significantly greater than that in control patients (relative Alzheimer values of threefold for layer III-V and twofold for layer VI; P < 0.05 in each case). The cortical laminar distribution of IL-1 alpha + microglia in Alzheimer patients correlated with the cortical laminar distribution of beta-amyloid precursor protein-immunoreactive (beta-APP+) neuritic plaques found in Alzheimer patients (r = 0.99, P < 0.005). Moreover, the cortical laminar distribution of IL-1 alpha + microglia in control patients also correlated with the cortical laminar distribution of beta-APP+ neuritic plaques found in Alzheimer patients (r = 0.91, P < 0.05). These correlations suggest that pre-existing laminar distribution patterns of IL-1 alpha + microglia (i.e. that seen in control patients) are important in determining the observed laminar distribution of beta-APP+ neuritic plaques in Alzheimer patients. These findings provide further support for our hypothesis that IL-1 is a key driving force in neuritic plaque formation in Alzheimer's disease.

Life-long overexpression of S100beta in Down's syndrome: implications for Alzheimer pathogenesis

Chronic overexpression of the neurite growth-promoting factor S100beta has been implicated in the pathogenesis of neuritic plaques in Alzheimer's disease. Such plaques are virtually universal in middle-aged Down's syndrome, making Down's a natural model of Alzheimer's disease. We determined numbers of astrocytes overexpressing S100beta, and of neurons overexpressing beta-amyloid precursor protein (beta-APP), and assayed for neurofibrillary tangles in neocortex of 20 Down's syndrome patients (17 weeks gestation to 68 years). Compared to controls, there were twice as many S100beta-immunoreactive (S100beta+) astrocytes in Down's patients at all ages: fetal, young, and adult (p = 0.01, or better, in each age group). These were activated (i.e., enlarged), and intensely immunoreactive, even in the fetal group. There were no neurofibrillary changes in fetal or young Down's patients. The numbers of S100beta+ astrocytes in young and adult Down's patients correlated with the numbers of neurons overexpressing beta-APP (p < 0.05). Our findings are consistent with the idea that conditions--including Down's syndrome--that promote chronic overexpression of S100beta may confer increased risk for later development of Alzheimer's disease.

Glial-neuronal interactions in Alzheimer's disease: the potential role of a 'cytokine cycle' in disease progression

The role of glial inflammatory processes in Alzheimer's disease has been highlighted by recent epidemiological work establishing head trauma as an important risk factor, and the use of anti-inflammatory agents as an important ameliorating factor, in this disease. This review advances the hypothesis that chronic activation of glial inflammatory processes, arising from genetic or environmental insults to neurons and accompanied by chronic elaboration of neuroactive glia-derived cytokines and other proteins, sets in motion a cytokine cycle of cellular and molecular events with neurodegenerative consequences. In this cycle, interleukin-1 is a key initiating and coordinating agent. Interleukin-1 promotes neuronal synthesis and processing of the beta-amyloid precursor protein, thus favoring continuing deposition of beta-amyloid, and activates astrocytes and promotes astrocytic synthesis and release of a number of inflammatory and neuroactive molecules. One of these, S100beta, is a neurite growth-promoting cytokine that stresses neurons through its trophic actions and fosters neuronal cell dysfunction and death by raising intraneuronal free calcium concentrations. Neuronal injury arising from these cytokine-induced neuronal insults can activate microglia with further overexpression of interleukin-1, thus producing feedback amplification and self-propagation of this cytokine cycle. Additional feedback amplification is provided through other elements of the cycle. Chronic propagation of this cytokine cycle represents a possible mechanism for progression of neurodegenerative changes culminating in Alzheimer's disease.

Quantification of Alzheimer-type neurofibrillary lesions by automated image analysis

Neurofibrillary pathology is seen in a wide variety of disorders such as Alzheimer's disease (AD), progressive supranuclear palsy and the Parkinsonism-dementia amyotrophic lateral sclerosis complex of Guam. To assess the pathological importance of these lesions quantitative studies need to be undertaken. To date, most neuropathological studies have been based on qualitative, or at best semi-quantitative, data reporting the presence or absence of specific lesion types. To obtain such data traditionally involves laborious manual measurements, which rely heavily on the skill of the investigator and tend to have low inter- and intra-rater reliabilities. We have developed a novel analysis technique, using colour image analysis, which can accurately quantify the total amount of neurofibrillary damage present. Furthermore we have developed a set of mathematically defined morphological criteria to allow objective discrimination between the three types of neurofibrillary damage seen in the cortex immunostained with Alz-50. Use of this novel technique provides a reliable, rational means for the classification of neurofibrillary lesions.

Comparative investigation of neurofibrillary damage in the temporal lobe in Alzheimer's disease, Down's syndrome and dementia pugilistica

Neurofibrillary lesions such as neurofibrillary tangles, neurites and neuropil threads are used as neuropathological markers of Alzheimer's disease (AD). However these lesions are also seen in non-demented elderly cases as well as in several other disorders such as Down's syndrome (DS), dementia pugilistica (DP) and Parkinson's disease. Quantitative studies may therefore help in understanding the pathophysiological role of these lesions. Using a novel image analysis technique we have quantified the extent of neurofibrillary damage in AD, DS and DP. We have found that the extent of neurofibrillary change did not significantly differ between AD and DS, though there were also strong parallels between AD and DP. We conclude that both genetic (as in DS) and environmental (as in DP) risk factors for AD-type pathology provide a similar pattern of neurofibrillary degeneration to that in AD itself suggesting that similar degenerative mechanisms might be triggered in all three conditions.

A quantitative comparison of plaque types in Alzheimer's disease and senile dementia of the Lewy body type

In a previous study we reported no difference in the overall beta-amyloid protein (beta AP) load between Alzheimer's disease (AD) and senile dementia of the Lewy body type (SDLT). However, it is possible that differences in the morphology of beta AP plaque types exist, analogous to the differences in cytoskeletal pathology found in these two disorders. We have carried out a quantitative image analysis of plaque subtypes in the temporal lobe of AD (n = 8), SDLT (n = 9) and control (n = 11) cases. Measurements of beta AP load and plaque density were consistently higher in AD and SDLT than in controls. When AD and SDLT cases were compared no differences were seen in either the density or relative proportions of classic and diffuse plaques. Based on these results we suggest that the variation in the clinical course of these diseases reflects differences in the cytoskeletal pathology, whereas the final stages of profound dementia common to both disorders is associated with the deposition of beta AP.

ApoE2 allele, Down's syndrome, and dementia

All individuals with Down's syndrome (trisomy 21-DS) develop the pathogenic hallmarks of Alzheimer's disease in old age (+40 years). The extent of pathology is variable, but it has been shown that the amount of beta-amyloid pathology is variable and related to age and the degree of dementia. Thus, in DS, growing old is associated with a progressive pathological process which results in cognitive decline. However, neuropsychological studies of older DS subjects have identified a clinical dementia in only a proportion of cases. These contradictory observations could be reconciled if some factor existed which modulated the rate and amount of beta-amyloid pathology. Recent studies demonstrate an association between the apolipoprotein E4 (ApoE4) allele and the earlier age of onset in both sporadic and familial AD. Increased amounts of beta-amyloid pathology can also be related to the E4 allele. However, at present there are no data documenting the effects of ApoE genotype on the expression or degree of clinical symptoms of the disease. We have examined the ApoE genotype in a cohort of clinically evaluated elderly patients with DS in order to examine the effects of ApoE genotype on the clinical symptoms of dementia. We report here that, despite the presence of an active disease process, the ApoE E2 allele is associated with longevity and preservation of cognitive functioning.

Altered beta-APP metabolism after head injury and its relationship to the aetiology of Alzheimer's disease

There is increasing evidence of a link between head injury and the subsequent onset of Alzheimer's disease. Deposits of amyloid beta-protein (A beta) are found not only in cases of dementia pugilistica but in some 30% of patients dying after a single episode of severe head injury. Detailed clinicopathological studies have shown that A beta deposition is most likely, but not exclusively, to occur, the older the patient at the time of injury, and if the injury is the result of a fall. Distribution studies have shown that the A beta is widely deposited in the neocortex and there is no apparent association with any of the multiple primary or secondary pathologies of traumatic brain injury. There is an increased expression of beta-APP particularly in the pre-alpha cells of the entorhinal cortex and in areas of axonal damage. Recent molecular genetic studies have shown that there is a strong association between deposits of A beta and the apolipoprotein E genotype of the individual.

Quantification of beta APP immunoreactive pre-alpha cells in the entorhinal cortex using image analysis

The neuropathological diagnosis of Alzheimer's disease requires an assessment of the quantity of pathology present. Advances in molecular biology have highlighted the role of beta-amyloid precursor protein (beta APP) in the pathogenesis of the disease. This protein is found in neurons and other cells and many neuropathological studies would benefit from a method which generates reliable data on the numbers of cells containing significant amounts of the protein. Classically, generation of such data would have involved laborious manual counting. This particular approach carries low levels of inter- and intra-rater reliability and is much dependent on the skill and experience of the operator. We have used immunocytochemistry to specifically define a single cell population, pre-alpha cells, containing beta APP, and have developed a computerized cell counting programme that can reliably quantify these cells in human post-mortem brain samples. We have obtained a high level of accuracy (> 95%) and efficiency in identifying and quantifying target cells and have demonstrated that our protocol can be used effectively by both novice and expert. This method could be easily configured to provide quantitative data for a wide range of immunocytochemically defined cell populations.

Schizophrenia. When neurons go astray

Recent prospective studies indicate that schizophrenia manifests itself in behavioural abnormalities much earlier than was previously thought, supporting the view that schizophrenia is a developmental disorder.

Increased numbers of beta APP-immunoreactive neurones in the entorhinal cortex after head injury

In a previous publication we hypothesized that Alzheimer's disease (AD) can be induced by the age-related increase in expression of beta-amyloid precursor protein (beta APP) in the medial temporal lobe. Head injury has also been identified as a risk factor for AD and as such, similarities should exist between the pathology found after head injury and the earliest stages of pathology in AD. In this study, we have quantified the number of beta APP-immunoreactive neurones in the medial temporal cortex (pre-alpha cells, layer II) of 13 head injured and 17 control patients. Significantly more beta APP immunoreactive neurones were observed in head injury cases (mean 18.4 per cluster) compared with controls (mean 13.4 per cluster, p < 0.05). These data provide a mechanism to explain how an environmental event such as head injury can generate the same molecular pathology (increased neuronal beta APP) as is found in the earliest stages of AD.

Apolipoprotein E epsilon 2 allele promotes longevity and protects patients with Down's syndrome from dementia

Although individuals with Down's syndrome nearly always develop the clinical and pathological features of Alzheimer's disease, some clearly do not become demented despite living into their sixth and seventh decades. Genetic variation at the apolipoprotein E locus has recently been shown to be an important determinant of Alzheimer's disease, with the epsilon 4 allele having been shown to be associated with the disease and, at least in some cases, the epsilon 2 allele being negatively associated with the disease. Here we show, in a series of clinically assessed individuals with Down's syndrome, that the epsilon 2 allele of ApoE is associated with both longevity and the absence of clinical evidence of dementia. These data show that the clinical phenotype of Down's syndrome can be modulated by genes on chromosomes other than chromosome 21. The importance of this observation to the pathogenesis of Alzheimer's disease, both in Down's syndrome and in general, is discussed.

Differential synaptic loss in the cortex in Alzheimer's disease: a study using archival material

We have developed techniques to utilize immunocytochemical localization of synaptic protein (SNAP-25) in conjunction with image analysis to investigate synaptic loss in readily available archival material. Sections from 5 cortical regions were examined in cases of Alzheimer's disease (n = 7) and controls (n = 5). Image analysis was used to determine a relative synaptic index (RSI) and probe for changes in synaptic integrity. RSI value for cortical regions did not differ in controls. RSIs from sulci and gyri were significantly correlated in Brodmann areas 6, 9 and 18 (40 and 52 approached significance). Cases with Alzheimer's disease showed decreases in sulcal and gyral RSI values of between 60% (Brodmann area 6 < 0.01) and 10% (Brodmann area 18 > 0.4) and a lack of correlation in sulco-gyral values except in Brodmann area 18. We have demonstrated that synaptic pathology is heterogeneous with frontal cortex most and occipital cortex least affected. Sulci and gyri are affected to different degrees. The underlying cytoarchitecture of the cortex and its pattern of connectivity appears to have a considerable influence on the degree and extent of synaptic pathology.

Ubiquitination as a probe for neurodegeneration in the brain in schizophrenia: the prefrontal cortex

Abnormalities in brain structure and brain function have been described in schizophrenia. It is not yet known whether these are caused by an abnormality of brain development, some form of birth injury, or a neurodegenerative process. Using immunocytochemical methods and a marker for neurodegeneration (ubiquitin), we examined an area of prefrontal cortex from elderly schizophrenic and control subjects for the presence of ubiquitin-positive degeneration products. There was no statistical difference in the degree of ubiquitination between the control and the patient samples. The findings provide no evidence to support a neurodegenerative process.

Differential pattern of beta-amyloid protein deposition within cortical sulci and gyri in Alzheimer's disease

We have quantified the pattern of beta-amyloid protein (beta AP) deposition in the sulci and gyri of the frontal cortex in Alzheimer's disease. The distribution pattern in the frontal cortex gyri is unequivocally different from the pattern found in the frontal sulci. These findings, in conjunction with our previous studies, reflect a differential vulnerability between the sulci and the gyri with respect to Alzheimer's disease pathology, sulci being affected to a greater extent. It is probable that the different patterns of deposition relate to the underlying cytoarchitecture of the cortex.

Synaptic degeneration is the primary neuropathological feature in prion disease: a preliminary study

The range of neuropathology found in cases of prion disease is considerable. The pathology present in dendrites and axons is associated with a marked loss of spines and synaptic contacts. It is probable that this loss underlies the functional and neurological deficits in the disease. Immunocytochemical re-examination of 2 cases of inherited disease with a 144 bp prion gene insertion with no characteristic pathology (i.e. spongiform change, astrocytosis and gliosis), together with 3 typical cases of prion disease (CJD), with antibodies to synaptophysin and synaptic protein demonstrated the presence of synaptic "plaque-like" lesions throughout the temporal cortex and cerebellum. In addition, examining the tissue by image analysis demonstrated a greater than 30% reduction in the relative synaptic index in all the prior disease cases when compared with controls. Synaptic disorganization and/or loss is a fundamental and constant feature of prion disease, irrespective of the presence or absence of spongiform change, neuronal loss and severe gliosis. Assessment of the extent and location of synaptic deficits might produce a more accurate documentation of the degree of neuronal disorganisation occurring during the course of prion disease.

On the origin of Alzheimer's disease: a hypothesis

There is no unifying hypothesis to account for the anatomical distribution of neuropathology, the involvement of beta-amyloid precursor protein (beta APP) and the role of increasing age in triggering the Alzheimer disease process. We report here that layer II pre-alpha neurones in transentorhinal and entorhinal cortex contain more beta APP immunoreactivity than other cortical neurones in normal individuals. This immunoreactivity increased in the early stages of Alzheimer's disease and was lost as the disease progressed. These neurones are known to undergo genetically programmed re-sprouting and synaptogenesis during the fifth and sixth decades of life. We hypothesize that these phenomena are related and that the Alzheimer's disease process originates in entorhinal cortex neurones due to the enhancement of their normally high content of beta APP during age-related resprouting.

Quantification of plaque types in sulci and gyri of the medial frontal lobe in patients with Alzheimer's disease

beta-Amyloid protein (beta A4) deposition was characterised in the sulci and gyri of frontal cortex in 14 cases of Alzheimer's disease. A quantitative study was made of two distinct plaque sub-types (diffuse and classic) using immunocytochemistry and image analysis using a discriminant function design. As reported previously more beta A4 was observed in sulci than gyri. Diffuse plaques were more numerous than classic plaques in sulci and gyri (P less than 0.01). Classic plaques were more abundant in the sulci (P less than 0.01). Increased beta A4 deposition in the sulci is accounted for by increased numbers of classic plaques. No correlation was observed between the numbers of diffuse and classic plaques in either region. Our data suggest that the two plaque types form discrete populations and that their evolution is governed by distinct pathophysiological parameters.

Quantification of beta A4 protein deposition in the medial temporal lobe: a comparison of Alzheimer's disease and senile dementia of the Lewy body type

The distribution of beta-amyloid protein (beta A4) was examined in the medial temporal lobes from cases of Alzheimer's disease (AD) (n = 13), senile dementia of Lewy body type (SDLT) (n = 12) and age matched controls (n = 9). Using a previously described image analysis technique the extent of beta A4 pathology was determined in ten distinct anatomical sites within the medial temporal lobe. AD and SDLT cases contained very similar amounts of beta A4 in the areas sampled and both contained significantly more beta A4 than the age matched controls, particularly in the dentate and parahippocampal gyri. The similarity of the beta A4 load in the two conditions is in contrast to reported differences in the number of neurofibrillary tangles which can be observed. It is suggested that AD and SDLT represent a spectrum of pathology which centres around the aberrant processing of the beta A4 precursor protein.

Regionally selective deficits in uptake sites for glutamate and gamma-aminobutyric acid in the basal ganglia in schizophrenia

In a post-mortem study of schizophrenic and control subjects, the sodium-dependent binding of D-[3H]aspartate and [3H]nipecotic acid were used to investigate uptake sites of glutamate and gamma-aminobutyric acid (GABA), respectively, in subcortical brain regions. Binding to the glutamate uptake site was substantially reduced in both the putamen and lateral pallidum of the schizophrenic subjects. Binding to the GABA uptake site was substantially reduced in the putamen; smaller reductions were apparent in the caudate nucleus and lateral pallidum. The results suggest that glutamatergic and GABAergic mechanisms in the basal ganglia are abnormal in schizophrenia. These abnormalities could be relevant to the development of psychosis but could also relate to the spectrum of mild motor disturbances often described in the disease.

Quantifying the pattern of beta/A4 amyloid protein distribution in Alzheimer's disease by image analysis

We have undertaken a study of the distribution of the beta/A4 amyloid deposited in the cerebral cortex in Alzheimer's disease. Previous studies which have examined the differential distribution of amyloid in the cortex in order to determine the laminar pattern of cortical pathology have not proved to be conclusive. We have developed an alternative method for the solution of this problem. It involves the immunostaining of sections followed by computer-enhanced image analysis. A mathematical model is then used to describe both the amount and the pattern of amyloid across the cortex. This method is both accurate and reliable and also removes many of the problems concerning inter and intra-rater variability in measurement. This method will provide the basis for further quantitative studies on the differential distribution of amyloid in Alzheimer's disease and other cases of dementia where cerebral amyloidosis occurs.

Alterations in phencyclidine and sigma binding sites in schizophrenic brains. Effects of disease process and neuroleptic medication

The specific binding of [3H]TCP and [3H](+)3-PPP, radioligands which respectively label PCP-NMDA and sigma binding sites was measured in tissue homogenates prepared from dissected areas of control and schizophrenic postmortem brains. [3H]TCP binding was bilaterally increased in orbital frontal cortex (Brodmann area 11) of schizophrenic brains. This finding may be due to an increased glutamatergic innervation of orbital frontal cortex since it parallels our findings of increased [3H]kainate and [3H]D-aspartate binding in this area. In contrast, [3H](+)3-PPP binding was reduced in each of the four brain regions examined. The reductions were greatest in brains from the schizophrenic subjects receiving neuroleptics at the time of death. Neuroleptics remaining in the brains of these subjects may compete in vitro with [3H](+)3-PPP for binding to the sigma site.

Analysis of laminar distribution of kappa opiate receptor in human cortex: comparison between schizophrenia and normal

Quantitative receptor autoradiography using the ligand [3H]U 69593 and tritium sensitive film was used to visualize the kappa subtype of opiate receptor in sections from 4 normal human postmortem brains. Data obtained from cortical scans, which measured receptor densities across the left and right parahippocampal gyri, were subject to Fourier analysis. This revealed that the kappa receptor distribution was described by a curve having significant first and second component harmonics. This analysis method can be used to describe a binding pattern mathematically, thus enabling a comparison to be made between normal and diseased brains. The same analysis was applied to [3H]U 69593 autoradiograms prepared from sections of 4 schizophrenic postmortem brains. The kappa receptor distribution in the schizophrenic group not only failed to produce the same pattern as the controls, but also showed no consistent pattern within the group. The method described can be used to investigate alterations in receptor distribution which occur in neuropsychiatric diseases involving neuronal dysplasia or atrophy.

Some morphometric observations on the brains of patients with Down's syndrome: their relationship to age and dementia

The number of senile plaques (SP) and neurofibrillary tangles (NFT) and the number and nucleolar volume of nerve cells have been estimated in certain cortical and subcortical regions in 22 patients with Down's syndrome (DS) and have been related to the patients' age and to the presence and severity of dementia. Elderly (i.e. over 50 years of age) patients showed increased densities of SP and NFT and significant reductions in number and nucleolar volume of nerve cells, when compared with patients under 50 years of age, though the extent of these changes was, in general, no greater in the non-demented elderly group than that in the demented elderly group. Of the younger, nondemented group, those patients with a limited formation of SP and NFT in their brains showed a similar number and nucleolar volume of nerve cells, as those completely devoid of SP and NFT. It is concluded that in DS, formation of SP and NFT predate any significant atrophy and loss of nerve cells and that it is only after the age of 50 years that gross atrophy and loss of neurones occurs, though the extent of this process seemingly does not predict the onset, nor the progress, of dementia.

Reduced GABA uptake sites in the temporal lobe in schizophrenia

The binding of [3H]nipecotic acid, a ligand for labelling GABA uptake sites in brain, was measured in left and right frontal cortex, polar temporal cortex, hippocampus and amygdala from control and schizophrenic postmortem brains. In schizophrenic brains, single concentration [3H]nipecotic acid binding was reduced bilaterally in amygdala and hippocampus and on the left side only in polar temporal cortex. These data suggest that GABA neurones are involved in the cerebral atrophy of schizophrenia and, in agreement with other studies, that this process is most pronounced in left temporal cortex.

Frontal cortical and left temporal glutamatergic dysfunction in schizophrenia

Glutamatergic mechanisms have been investigated in postmortem brain samples from schizophrenics and controls. D-[3H]Aspartate binding to glutamate uptake sites was used as a marker for glutamatergic neurones, and [3H]kainate binding for a subclass of postsynaptic glutamate receptors. There were highly significant increases in the binding of both ligands to membranes from orbital frontal cortex on both the left and right sides of schizophrenic brains. The changes are unlikely to be due to antemortem neuroleptic drug treatment, because no similar changes were recorded in other areas. A predicted left-sided reduction in D-[3H]aspartate binding was refuted at 5% probability, but not at 10%. Previously reported high concentrations of dopamine in left amygdala were strongly associated with low concentrations of D-[3H]aspartate binding in left polar temporal cortex in the schizophrenics. The findings are compatible with an overabundant glutamatergic innervation of orbital frontal cortex in schizophrenia. The results also suggest that schizophrenia may involve left-sided abnormalities in the relationship between temporal glutamatergic and dopaminergic projections to amygdala.

Reduced D-[3H]aspartate binding in Down's syndrome brains

The binding of D-[3H]aspartate to glutamate uptake sites was measured in post-mortem brains from subjects with Down's syndrome (DS) and age-matched controls. DS brains had substantially reduced D-[3H]aspartate binding in the frontal and temporal cortex, hippocampus and caudate nucleus. There was no correlation between the numbers of Alzheimer-like plaques and tangles or clinically-assessed dementia and D-[3H]aspartate binding in DS brains. The binding of [3H]N-(1-[2-thienyl]cyclohexyl)piperidine ([3H]TCP) to postsynaptic N-methyl-D-aspartate sites was normal in DS brains. This study suggests that the reduction in glutamate uptake sites in DS is more substantial and widespread than in Alzheimer's disease.

Regional changes in [3H]D-aspartate and [3H]TCP binding sites in Alzheimer's disease brains

The specific binding of [3H]D-aspartate, a marker for the presynaptic glutamate uptake site, and [3H]N-(1-[2-Thienyl]cyclohexyl)-piperidine [( 3H]TCP), a high affinity ligand for the N-methyl-D-aspartate (NMDA)-associated phencyclidine binding site, was measured in homogenates of brain from normal subjects and from subjects with neuropathologically confirmed Alzheimer's disease. Alzheimer's disease was associated with a reduction in [3H]D-aspartate binding density in temporal cortex and caudate nucleus. By contrast, a reduction in the receptor density for [3H]TCP binding was only recorded in the frontal cortex. Thus, glutamate-containing nerve terminals are severely reduced in Alzheimer's disease, whilst the postsynaptic NMDA-phencyclidine receptor complex is much less affected. These findings have implications for theories of glutamate neurotoxicity in Alzheimer's disease.