Schizophrenia: a neuropathological perspective

Embracing variability in the search for biological mechanisms of psychiatric illness

Despite decades of research, we lack objective diagnostic or prognostic biomarkers of mental health problems. A key reason for this limited progress is a reliance on the traditional case-control paradigm, which assumes that each disorder has a single cause that can be uncovered by comparing average phenotypic values of patient and control samples. Here, we discuss the problematic assumptions on which this paradigm is based and highlight recent efforts that seek to characterize, rather than minimize, the inherent clinical and biological variability that underpins psychiatric populations. Embracing such variability is necessary to understand pathophysiological mechanisms and develop more targeted and effective treatments.

Relationships Among Retinal Nerve Fiber Layer Thickness, Vascular Endothelial Growth Factor, and Cognitive Impairment in Patients with Schizophrenia

BACKGROUND

Studies have suggested retinal nerve fiber layer (RNFL) involvement in the pathogenesis of schizophrenia. Additionally, research has shown that vascular endothelial growth factor (VEGF) potentially contributes to the pathophysiology of psychiatric disorders. Therefore, this study aimed to investigate VEGF, RNFL, and correlations with cognitive impairments in schizophrenia patients.

METHODS

Patients with schizophrenia (n = 138) were compared to healthy controls (n = 160). RNFLs were measured with optical coherence tomography (OCT). The Stroop color and word test (SCWT) was used to evaluate neurocognition. Blood samples were collected to measure VEGF. SPSS 20.0 was used to perform analysis of covariance, t-tests, partial correlation analysis, and linear regression.

RESULTS

Thinner RNFLs were found in schizophrenia patients (p < 0.001). RNFL showed a significant correlation with SCWT scores (all p < 0.05). Serum level of VEGF was lower in patients with schizophrenia (p = 0.010). Total and inferior RNFL thicknesses of right eyes were positively correlated to VEGF level (RNFL total thickness p = 0.032, inferior thickness p = 0.014).Total RNFL thicknesses were shown to be reduced following a prolonged duration of illness (both p < 0.01).

CONCLUSION

These findings suggest that patients with schizophrenia have degeneration with RNFL thickness following illness duration, which may contribute to neurocognitive impairments observed in schizophrenia. VEGF is speculated to play some important role on RNFL degeneration with schizophrenia patients.

Impact of Proliferator-Activated Receptor γ Gene Polymorphisms on Risk of Schizophrenia: A Case-Control Study and Computational Analyses

Objective: Schizophrenia (SCZ) is a common psychiatric disorder characterized by a complex mode of inheritance. Peroxisome proliferator-activated receptor-γ (PPARG) mainly regulates lipid and glucose metabolisms while it is constitutively expressed in rat primary microglial cultures. This preliminary study was aimed to investigate the relationship of two polymorphisms in the PPARG gene, rs1801282 C/G, and rs3856806 C/T, to the risk of SCZ in the southeast Iranian population.

Method: A total of 300 participants (150 patients with SCZ and 150 healthy controls) were enrolled. Genotyping was done using the amplification refractory mutation system polymerase chain reaction (ARMS–PCR) technique. Computational analyses were carried out to predict the potential effects of the studied polymorphisms.

Results: A significant link was found between genotypes of rs1801282 and SCZ susceptibility. The G allele of rs1801282 in CG and GG form of the codominant model increased the risk of SCZ by 2.49 and 2.64 folds, respectively. With regards to rs3856806, enhanced risk of SCZ was also observed under different inheritance models except for the overdominant model. Also, the T allele of rs3856806 enhanced the risk of SCZ by 3.19 fold. Computational analyses predicted that rs1801282 polymorphism might alter the secondary structure of PPARG-mRNA and protein function. At the same time, the other variant created the binding sites for some enhancer and silencer motifs.

Conclusion: Our findings showed that PPARG rs1821282 and rs3856806 polymorphisms associate with SCZ susceptibility. Replication studies in different ethnicities with a larger population are needed to validate our findings.

Obstetric complications in distinct schizophrenic subgroups

In 55 chronic DSM III-R schizophrenics the occurrence of obstetric complications (OCs) was investigated using the familial/sporadic strategy and Leonhard's unsystematic/systematic distinction. The overall frequency and severity of OCs did not differ between patients and controls. A sub-sample of patients, whose genetic risk was supposed to be high in both classification systems (diagnosis of unsystematic and familial schizophrenia), had significantly fewer OCs than controls on the Lewis and Murray scale (P< 0.05). With reference to previous reports of increased mortality rates in the offspring of schizophrenics, high genetic risk and additional perinatal stressors may increase perinatal mortality. In contrast, patients whose genetic risk was supposed to be low in both systems (diagnosis of systematic and sporadic schizophrenia) showed a trend to an increased frequency of OCs in the Fuchs scale. In the context of the recently reported highly significantly increased rate of maternal infections during midgestation in these patients, it was supposed that perinatal complications may be of some aetiological importance in schizophrenics with low genetic risk.

Impact of short-term temperature variability on emergency hospital admissions for schizophrenia stratified by season of birth

Diurnal temperature range (DTR) and temperature change between neighboring days (TCN) are important meteorological indicators closely associated with global climate change. However, up to date, there have been no studies addressing the impacts of both DTR and TCN on emergency hospital admissions for schizophrenia. We conducted a time-series analysis to assess the relationship between temperature variability and daily schizophrenia onset in Hefei, an inland city in southeast China. Daily meteorological data and emergency hospital admissions for schizophrenia from 2005 to 2014 in Hefei were collected. After stratifying by season of birth, Poisson generalized linear regression combined with distributed lag nonlinear model (DLNM) was used to examine the relationship between temperature variability and schizophrenia, adjusting for long-term trend and seasonality, mean temperature, and relative humidity. Our analysis revealed that extreme temperature variability may increase the risk for schizophrenia onset among patients born in spring, while no such association was found in patients born in summer and autumn. In patients born in spring, the relative risks of extremely high DTR comparing the 95th and 99th percentiles with the reference (50th, 10 °C) at 3-day lag were 1.078 (95 % confidence interval (CI) 1.025-1.135) and 1.159 (95 % CI 1.050-1.279), respectively. For TCN effects, only comparing 99th percentile with reference (50th, 0.7 °C) was significantly associated with emergency hospital admissions for schizophrenia (relative risk (RR) 1.111, 95 % CI 1.002-1.231). This study suggested that exposure to extreme temperature variability in short-term may trigger later days of schizophrenia onset for patients born in spring, which may have important implications for developing intervention strategies to prevent large temperature variability exposure.

Reductionistic Biological Thinking and the Denial of Experience and Pain in Developmental Theories

The article questions current biological research in the behavioral field for both its reductionistic thinking as well as its disregard of the developmental process. The process of development cannot be understood merely as an unfolding of genetic forces. Research strategies attempting to do so distort the view of the actual relation of such forces to behavioral events. In doing so, they do violence to our views both of humans and of science. The quest for "objectivity" has blinded us to the obvious facts of our experience. This, in turn, has led to a pervasive misconception that controlling an emotion, such as pain, is the same as understanding what that emotion is as well as sharing it empathically. We have come to thinkwe know what is inborn and innate on the basis of a misconceived view of development. Such thinking expresses a generalized denial and devaluation of feelings.

Brain network informed subject community detection in early-onset schizophrenia

Early-onset schizophrenia (EOS) offers a unique opportunity to study pathophysiological mechanisms and development of schizophrenia. Using 26 drug-naïve, first-episode EOS patients and 25 age- and gender-matched control subjects, we examined intrinsic connectivity network (ICN) deficits underlying EOS. Due to the emerging inconsistency between behavior-based psychiatric disease classification system and the underlying brain dysfunctions, we applied a fully data-driven approach to investigate whether the subjects can be grouped into highly homogeneous communities according to the characteristics of their ICNs. The resultant subject communities and the representative characteristics of ICNs were then associated with the clinical diagnosis and multivariate symptom patterns. A default mode ICN was statistically absent in EOS patients. Another frontotemporal ICN further distinguished EOS patients with predominantly negative symptoms. Connectivity patterns of this second network for the EOS patients with predominantly positive symptom were highly similar to typically developing controls. Our post-hoc functional connectivity modeling confirmed that connectivity strength in this frontotemporal circuit was significantly modulated by relative severity of positive and negative syndromes in EOS. This study presents a novel subtype discovery approach based on brain networks and proposes complex links between brain networks and symptom patterns in EOS.

The neuroimmunology of schizophrenia

Schizophrenia (SCZ) is a polygenic, multi-factorial disorder and a definitive understanding of its pathophysiology has been lacking since it was first described more than a century ago. The predominant pharmacological approach used to treat SCZ is the use of dopamine receptor antagonists. The fact that many patients remain symptomatic, despite complying with medication regimens, emphasises the need for a more encompassing explanation for both the causes and treatment of SCZ. Recent neuroanatomical, neurobiological, environmental and genetic studies have revived the idea that inflammatory pathways are involved in the pathogenesis of SCZ. These new insights have emerged from multiple lines of evidence, including the levels of inflammatory proteins in the central nervous system of patients with SCZ and animal models. This review focuses on aberrant inflammatory mechanisms present both before and during the onset of the psychotic symptoms that characterise SCZ and discusses recent research into adjunctive immune system modulating therapies for its more effective treatment.

Is lead exposure in early life an environmental risk factor for Schizophrenia? Neurobiological connections and testable hypotheses

Schizophrenia is a devastating neuropsychiatric disorder of unknown etiology. There is general agreement in the scientific community that schizophrenia is a disorder of neurodevelopmental origin in which both genes and environmental factors come together to produce a schizophrenia phenotype later in life. The challenging questions have been which genes and what environmental factors? Although there is evidence that different chromosome loci and several genes impart susceptibility for schizophrenia; and epidemiological studies point to broad aspects of the environment, only recently there has been an interest in studying gene × environment interactions. Recent evidence of a potential association between prenatal lead (Pb(2+)) exposure and schizophrenia precipitated the search for plausible neurobiological connections. The most promising connection is that in schizophrenia and in developmental Pb(2+) exposure there is strong evidence for hypoactivity of the N-methyl-d-aspartate (NMDA) subtype of excitatory amino acid receptors as an underlying neurobiological mechanism in both conditions. A hypofunction of the NMDA receptor (NMDAR) complex during critical periods of development may alter neurobiological processes that are essential for brain growth and wiring, synaptic plasticity and cognitive and behavioral outcomes associated with schizophrenia. We also describe on-going proof of concept gene-environment interaction studies of early life Pb(2+) exposure in mice expressing the human mutant form of the disrupted in schizophrenia 1 (DISC-1) gene, a gene that is strongly associated with schizophrenia and allied mental disorders.

Effect of transient blockade of N-methyl-D-aspartate receptors at neonatal stage on stress-induced lactate metabolism in the medial prefrontal cortex of adult rats: role of 5-HT1A receptor agonism

Decreased activity of the medial prefrontal cortex (mPFC) has been considered a basis for core symptoms of schizophrenia, an illness associated with a neurodevelopmental origin. Evidence from preclinical and clinical studies indicates that serotonin (5-HT)1A receptors play a crucial role in the energy metabolism of the mPFC. This study was undertaken to determine (1) if transient blockade of N-methyl-D-aspartate receptors during the neonatal stage inhibit energy demands in response to stress, as measured by extracellular lactate concentrations, in the mPFC at the young adult stage, and (2) if tandospirone, a 5-HT1A partial agonist, reverses the effect of the neonatal insult on energy metabolism. Male pups received MK-801 (0.20 mg/kg) on postnatal days (PDs) 7-10. On PD 63, footshock stress-induced lactate levels were measured using in vivo microdialysis technique. Tandospirone (0.1, 1.0, and 5.0 mg/kg) was administered once daily for 14 days before the measurement of lactate levels. Neonatal MK-801 treatment suppressed footshock stress-induced lactate production in the mPFC, but not caudate-putamen, whereas basal lactate levels were not significantly changed in either brain region. The MK-801-induced suppression of footshock stress-induced lactate production in the mPFC was attenuated by tandospirone at 1.0mg/kg/day, but not 0.1 or 5.0 mg/kg/day, which is an effect antagonized by coadministration of WAY-100635, a selective 5-HT1A antagonist. These results suggest a role for impaired lactate metabolism in some of the core symptoms of schizophrenia, for example, negative symptoms and cognitive deficits. The implications for the ability of 5-HT1A agonism to ameliorate impaired lactate production in the mPFC of this animal model are discussed.

A brief review on recent developments in animal models of schizophrenia

Number of patients suffering from schizophrenia is increasing daily, subsequently, increasing the need of proper medication to treat the symptoms and eventually improve the patients' condition. However, all the progress for designing or discovering medication comes to a standstill, as the symptomatic treatment can only be done in the patients, but performing clinical trials with all the possible candidate drugs in human beings and patients is unethical. Thus, the need arises for proper animal and non-human primate animal models of the disease, which would not only serve the purpose of understanding the disease in a better physiological setting, but also would allow the scientists to focus on developing a therapeutically effective and potent medication for treating this hazardous disease. This brief review article focuses on a few animal models which are generally used for carrying out studies on schizophrenic symptoms in research labs and industry worldwide. The paper also tries to validate the pre-clinically available models based on certain specified criteria like the predictive constructive and face validity. Thus, the paper gives guidance toward the mechanistic and traditional models of schizophrenia applying some of the newer principles and helps researchers in deciding a particular relevant model for their own purpose.

Neonatal exposure to MK-801, an N-methyl-D-aspartate receptor antagonist, enhances methamphetamine-induced locomotion and disrupts sensorimotor gating in pre- and postpubertal rats

Administration of non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists (e.g. phencyclidine, MK-801) has been shown to elicit behavioral abnormalities related to symptoms of schizophrenia, such as spontaneous locomotor activity and impaired sensorimotor gating, as represented by deficits of prepulse inhibition (PPI). We sought to determine whether transient blockade of NMDA receptors at the neonatal stage would produce dopamine supersensitivity around puberty, as manifested by these behavioral measures. For this purpose, we examined methamphetamine (MAP; 1.0mg/kg, i.p.)-induced locomotor activity and PPI in pre- (postnatal day; PD 36-38) or post- (PD 64-66) puberty in rats administered MK-801 (0.2mg/kg/day, s.c.) between PD 7 and PD 10. Neonatal MK-801 treatment augmented MAP-induced hyperlocomotion especially in the early adulthood, whereas spontaneous locomotor activity and rearing were not changed. MK-801 administration also disrupted PPI without affecting startle amplitudes around puberty. These findings suggest that transient exposure to MK-801 in the neonatal stage causes exaggerated dopamine transmission and cognitive deficits, particularly in the post-puberty stage.

Long-term effects of neonatal MK-801 treatment on prepulse inhibition in young adult rats

RATIONALE

Blockade of N-methyl-D-asparate (NMDA) receptors has been shown to produce some of the abnormal behaviors related to symptoms of schizophrenia in rodents and human. Neonatal treatment of rats with non-competitive NMDA antagonists has been shown to induce behavioral abnormality in a later period.

OBJECTIVES

The aim of this study was to determine whether brief disruption of NMDA receptor function during a critical stage of development is sufficient to produce sensorimotor-gating deficits in the late adolescence or early adulthood in the rat.

METHODS

Male pups received the NMDA receptor blocker MK-801 (0.13 or 0.20 mg/kg), or an equal volume of saline on postnatal day (PD) 7 through 10. The animals were tested twice for prepulse inhibition (PPI) and locomotor activity in pre- (PD 35-38) and post- (PD 56-59) puberty.

RESULTS

Neonatal exposure to both doses MK-801 disrupted PPI in the adolescence and early adulthood. Low-dose MK-801 elicited long-term effects on startle amplitudes, whereas high-dose MK-801 did not. Neither dose of MK-801 showed a significant effect on spontaneous locomotor activity, whereas the high dose attenuated rearing.

CONCLUSIONS

The results of this study suggest neonatal exposure to MK-801 disrupted sensorimotor gating in the adolescence and early adulthood stages. These findings indicate that rats transiently exposed to NMDA blockers in neonatal periods are useful for the study of the pathophysiology and treatment of schizophrenia.

Spatio-temporal EEG waves in first episode schizophrenia

OBJECTIVE

Schizophrenia is characterized by a deficit in context processing, with physiological correlates of hypofrontality and reduced amplitude P3b event-related potentials. We hypothesized an additional physiological correlate: differences in the spatio-temporal dynamics of cortical activity along the anterior-posterior axis of the scalp.

METHODS

This study assessed latency topographies of spatio-temporal waves under task conditions that elicit the P3b. EEG was recorded during separate auditory and visual tasks. Event-related spatio-temporal waves were quantified from scalp EEG of subjects with first episode schizophrenia (FES) and matched controls.

RESULTS

The P3b-related task conditions elicited a peak in spatio-temporal waves in the delta band at a similar latency to the P3b event-related potential. Subjects with FES had fewer episodes of anterior to posterior waves in the 2-4 Hz band compared to controls. Within the FES group, a tendency for fewer episodes of anterior to posterior waves was associated with high Psychomotor Poverty symptom factor scores.

CONCLUSIONS

Subjects with FES had altered global EEG dynamics along the anterior-posterior axis during task conditions involving context update.

SIGNIFICANCE

The directional nature of this finding and its association with Psychomotor Poverty suggest this result is related to findings of hypofrontality in schizophrenia.

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.

Prenatal exposure to an NMDA receptor antagonist, MK-801 reduces density of parvalbumin-immunoreactive GABAergic neurons in the medial prefrontal cortex and enhances phencyclidine-induced hyperlocomotion but not behavioral sensitization to methamphetamine in postpubertal rats

RATIONALE

Neurodevelopmental deficits of parvalbumin-immunoreactive gamma-aminobutyric acid (GABA)ergic interneurons in prefrontal cortex have been reported in schizophrenia. Glutamate influences the proliferation of this type of interneuron by an N-methyl-D-aspartate (NMDA)-receptor-mediated mechanism. The present study hypothesized that prenatal blockade of NMDA receptors would disrupt GABAergic neurodevelopment, resulting in differences in effects on behavioral responses to a noncompetitive NMDA antagonist, phencyclidine (PCP), and a dopamine releaser, methamphetamine (METH).

METHODS

GABAergic neurons were immunohistochemically stained with parvalbumin antibody. Psychostimulant-induced hyperlocomotion was measured using an infrared sensor.

RESULTS

Prenatal exposure (E15-E18) to the NMDA receptor antagonist MK-801 reduced the density of parvalbumin-immunoreactive neurons in rat medial prefrontal cortex on postnatal day 63 (P63) and enhanced PCP-induced hyperlocomotion but not the acute effects of METH on P63 or the development of behavioral sensitization. Prenatal exposure to MK-801 reduced the number of parvalbumin-immunoreactive neurons even on postnatal day 35 (P35) and did not enhance PCP-induced hyperlocomotion, the acute effects of METH on P35, or the development of behavioral sensitization to METH.

CONCLUSIONS

These findings suggest that prenatal blockade of NMDA receptors disrupts GABAergic neurodevelopment in medial prefrontal cortex, and that this disruption of GABAergic development may be related to the enhancement of the locomotion-inducing effect of PCP in postpubertal but not juvenile offspring. GABAergic deficit is unrelated to the effects of METH. This GABAergic neurodevelopmental disruption and the enhanced PCP-induced hyperlocomotion in adult offspring prenatally exposed to MK-801 may prove useful as a new model of the neurodevelopmental process of pathogenesis of treatment-resistant schizophrenia via an NMDA-receptor-mediated hypoglutamatergic mechanism.

Effect of prefrontal cortex inactivation on behavioral and neurochemical abnormalities in rats with excitotoxic lesions of the entorhinal cortex

Morphological studies report reductions in the volume of medial temporal lobe structures and the prefrontal cortex in subjects with schizophrenia. The present study was performed to clarify the role of prefrontal-temporo-limbic system in the manifestation of psychosis, using entorhinal cortical lesion rats as a vulnerability animal model. Quinolinic acid (lesion group) or phosphate buffer (sham group) was infused into the left entorhinal cortex (EC) of male Wistar rats. On the 28th postoperative day, methamphetamine (MAP; 1 mg/kg, i.p.)-induced dopamine (DA) release in the nucleus accumbens (NAC) and the basolateral amygdala (BLA), as well as locomotor activity and prepulse inhibition (PPI), was measured following microinfusion of lidocaine or the cerebrospinal fluid (CSF) into the medial prefrontal cortex (mPFC). Lesions of the EC resulted in enhancement of MAP-induced DA release in the NAC and BLA. Further analysis revealed that the enhancement by EC lesions of MAP-induce DA release in the NAC was particularly evident in the lidocaine-infused rats. EC lesions also enhanced MAP-induced locomotor activity, especially in the lidocaine-treated animals. By contrast, infusion of lidocaine into mPFC attenuated MAP-induced DA release in the BLA, irrespective of the lesion status. Both EC lesions and lidocaine infusion disrupted PPI. These results indicate that inactivation of the mPFC, as well as structural abnormalities in the EC, leads to dysregulation of DAergic neurotransmissions in the limbic regions. The implications of these findings in relation to the neural basis for psychosis vulnerability are discussed.

Hemisphere asymmetry in schizophrenia as revealed through line bisection, line trisection, and letter cancellation

Individuals with schizophrenia are known to demonstrate reduced or reversed brain asymmetry. While much is known regarding anatomical brain asymmetry, little is known about how this affects the individual at the functional level. Based on the known leftward bias in normal individuals, the aim of this study was to explore whether any difference in this function would be noted in schizophrenia. This study therefore investigated the phenomenon of functional asymmetry in schizophrenia patients by means of the following tasks: line bisection, line trisection (assessing hemifield spatial neglect) and letter cancellation (assessing contralateral visuospatial exploration). Forty-five schizophrenia inpatients maintained on antipsychotic medication were evaluated. Transections were measured for accuracy, lateralization, and directional bias. In the line bisection task subjects indicated no pseudo-neglect, thus differing from a normal, leftward bias. In the line trisection there was a significant preference to perform the ambiguous instruction on the right side, with no consistent bias in accuracy. Irrespective of conditions, in the letter cancellation task there was always a significant tendency to succeed on the left third compared to the right third. Results may support findings in schizophrenia indicating decreased or altered function of the left hemisphere.

Tonic modulation of inhibition by dopamine D4 receptors in the rat hippocampus

Dopaminergic pathways have been recognized to play a critical role in cognition and emotion. Dopamine D2 and D4 receptors are the target for most common antipsychotics and their activation, particularly those in the medial temporal lobe structures, has been associated with their beneficial actions. The entorhinal cortex, which is the cortical area most consistently and severely affected in schizophrenia constitutes the main input to the hippocampus. Since the D4 receptor is highly concentrated in the hippocampus, and the effects of the selective activation of D4 receptors on the input/output function of the hippocampal formation are poorly understood, we sought to investigate the role of these receptors in the synaptic transmission and paired-pulse inhibition from the perforant path to area CA1 and the dentate gyrus. The D4 receptor antagonist, clozapine, translated paired-pulse inhibition into paired-pulse potentiation in both perforant path targets. By contrast, the D2/D3 antagonist quinpirole had no effect. The blockade of the D2/3 receptors with sulpiride, and of D1/5 receptors with SCH-23390, has no effect on paired-pulse inhibition, suggesting that these receptors are not involved in feedforward inhibition in these hippocampal areas. Interestingly, the perfusion of the D4 selective antagonist, L-745,870 (Patel et al., 1997: J Pharmacol Exp Ther 283:636-647) during the blockade of D2/3 and D1/5 receptors produces a reversible decrease in paired-pulse inhibition in CA1, but not in the DG. Our results show that endogenous DA tonically modulates feedforward inhibition in area CA1 and the dentate gyrus through the activation of D4 receptors located in the interneuronal population of these hippocampal regions. Since activation of the D4 receptor inhibits GABA release and GABAergic synaptic transmission, we suggest that the perforant path stimulates interneurons that have the D4 receptor and that, in turn, contact other interneurons that synapse onto pyramidal cells. (c) 2004 Wiley-Liss, Inc.

Enhanced locomotor activity in rats with excitotoxic lesions of the entorhinal cortex, a neurodevelopmental animal model of schizophrenia: Behavioral and in vivo microdialysis studies

In order to examine the construct validity of rats with excitotoxic damage of the left entorhinal cortex (EC) as an animal model of schizophrenia, we measured dopamine (DA)-related behaviors and methamphetamine (MAP)-induced DA release in the accumbens nucleus (NAC) in these animals. Quinolinic acid (lesion group) or phosphate buffer (sham group) was infused into the left EC of adolescent (postnatal 7 weeks) male Wistar rats. On the 14th and 28th postoperative day, spontaneous and MAP (1 mg/kg, i.p.)-induced locomotor activities, as well as MAP-induced stereotypy, were measured. The lesioned rats exhibited significantly greater spontaneous or MAP-induced locomotor activity on both of the postoperative days than did sham-operated animals, while EC lesions did not affect MAP-induced stereotypy on either occasion. MAP (1 mg/kg, i.p.)-induced DA release in NAC was measured by in vivo microdialysis on the 28th postoperative day. Lesioned rats did not show a significant change in MAP (1 mg/kg, i.p.)-induced DA release in NAC compared to sham-operated animals. These results suggest that excitotoxic damage of the left EC produces behavioral changes consistent with altered mesolimbic dopaminergic transmissions, possibly mediated by postsynaptic supersensitivity.

The hippocampus in schizophrenia: a review of the neuropathological evidence and its pathophysiological implications

This paper puts the case for the hippocampus as being central to the neuropathology and pathophysiology of schizophrenia. The evidence comes from a range of approaches, both in vivo (neuropsychology, structural and functional imaging) and post mortem (histology, morphometry, gene expression, and neurochemistry). Neuropathologically, the main positive findings concern neuronal morphology, organisation, and presynaptic and dendritic parameters. The results are together suggestive of an altered synaptic circuitry or "wiring" within the hippocampus and its extrinsic connections, especially with the prefrontal cortex. These changes plausibly represent the anatomical component of the aberrant functional connectivity that underlies schizophrenia. Glutamatergic pathways are prominently but not exclusively affected. Changes appear somewhat greater in the left hippocampus than the right, and CA1 is relatively uninvolved compared to other subfields. Hippocampal pathology in schizophrenia may be due to genetic factors, aberrant neurodevelopment, and/or abnormal neural plasticity; it is not due to any recognised neurodegenerative process. Hippocampal involvement is likely to be associated with the neuropsychological impairments of schizophrenia rather than with its psychotic symptoms.

Inhibition of dopamine synthesis with alpha-methyl-p-tyrosine abolishes the enhancement of methamphetamine-induced extracellular dopamine levels in the amygdala of rats with excitotoxic lesions of the entorhinal cortex

This study was performed to investigate the mechanisms underlying the augmentation of methamphetamine (MAP)-induced dopamine (DA) release in the entorhinal cortex-lesioned rats. Quinolinic acid or phosphate buffered saline was infused into the left entorhinal cortex of adolescent rats (postnatal day 7 weeks). After 4 weeks of lesioning, acute MAP (2 mg/kg, i.p.)-induced DA release in the amygdala was significantly enhanced in lesioned rats compared to sham operated rats. Inhibition of DA synthesis by alpha-methyl-p-tyrosine, an inhibitor of catecholamine synthesis, resulted in abolishment of the enhancement of MAP (2 or 5 mg/kg, i.p.)-induced DA release in the amygdala of lesioned rats. These results suggest that excessive DA pool in nerve terminals underlies the augmentation of MAP-induced DA release in the amygdala of the lesioned rats.

Association between minor physical anomalies and lateral ventricular enlargement in childhood and adolescent onset schizophrenia

OBJECTIVE

The primary purpose of this study was to investigate the association between morphological abnormalities of brain and minor physical anomalies (MPAs) in childhood and adolescent onset schizophrenia.

METHOD

Twenty-seven patients who had been diagnosed with schizophrenia according to DSM-IV criteria before 18 years of age were included in the study. MPAs were evaluated with the modified version of Waldrop scale (WS) by Green et al. Morphological abnormalities of brain was evaluated with ventricular-brain ratio (VBR) by using cerebral magnetic resonance imaging (MRI) examination.

RESULTS

A significant positive correlation was observed between WS scores and VBRs.

CONCLUSION

This result indicates a relationship between MPAs and lateral ventricular enlargement, and supports neurodevelopmental etiology in childhood or adolescent onset schizophrenia.

Schizophrenia: from phenomenology to neurobiology

Schizophrenia is a common and debilitating illness, characterized by chronic psychotic symptoms and psychosocial impairment that exact considerable human and economic costs. The literature in electronic databases as well as citations and major articles are reviewed with respect to the phenomenology, pathology, treatment, genetics and neurobiology of schizophrenia. Although studied extensively from a clinical, psychological, biological and genetic perspective, our expanding knowledge of schizophrenia provides only an incomplete understanding of this complex disorder. Recent advances in neuroscience have allowed the confirmation or refutation of earlier findings in schizophrenia, and permit useful comparisons between the different levels of organization from which the illness has been studied. Schizophrenia is defined as a clinical syndrome that may include a collection of diseases that share a common presentation. Genetic factors are the most important in the etiology of the disease, with unknown environmental factors potentially modulating the expression of symptoms. Schizophrenia is a complex genetic disorder in which many genes may be implicated, with the possibility of gene-gene interactions and a diversity of genetic causes in different families or populations. A neurodevelopmental rather than degenerative process has received more empirical support as a general explanation of the pathophysiology, although simple dichotomies are not particularly helpful in such a complicated disease. Structural brain changes are present in vivo and post-mortem, with both histopathological and imaging studies in overall agreement that the temporal and frontal lobes of the cerebral cortex are the most affected. Functional imaging, neuropsychological testing and clinical observation are also generally consistent in demonstrating deficits in cognitive ability that correlate with abnormalities in the areas of the brain with structural abnormalities. The dopamine and other neurotransmitter systems are certainly involved in the treatment or modulation of psychotic symptoms. These broad findings represent the distillation of a large body of disparate data, but firm and specific findings are sparse, and much about schizophrenia remains unknown.

Anterior hippocampal volume reduction in male patients with schizophrenia

Quantitative high resolution magnetic resonance imaging (MRI) was utilized to measure anterior, posterior, and total hippocampal volumes in 27 male patients with chronic schizophrenia and 24 male controls. To optimize measurement techniques, hippocampal volumes were: (1) acquired with 1.4-mm slices; (2) excluded with the amygdala; (3) normalized for position; and (4) corrected for total intracranial volume (ICV). The results of a linear mixed effects regression analysis, which made it possible to analyze total anterior and total posterior hippocampal volumes separately, indicated that the anterior hippocampus was significantly smaller in the schizophrenic group relative to the control group. There were no significant group differences with respect to posterior hippocampal volumes, and no significant correlations between hippocampal volumes and illness duration. A significant lateralized asymmetry was also noted in both groups with the right hippocampal volume being larger than the left. These preliminary findings support a significant anterior hippocampal volume reduction in men with schizophrenia as well as a similar hippocampal volume asymmetry in both male controls and schizophrenics.

Minor physical anomalies in childhood and adolescent onset schizophrenia

A modified version of the Waldrop scale (WS) was used to assess the prevalence of minor physical anomalies in schizophrenic patients (n = 71) and healthy controls (n = 65). The mean total WS score was 3.32 (SD 1.98) for the schizophrenic patients, significantly higher than that for the controls (2.19, SD 1.18). Minor physical anomalies were compared between two schizophrenic groups, divided on the basis of age at onset, early onset schizophrenia (EOS, onset under age 18 years) group and late onset schizophrenia (LOS, onset at or above age 20 years) group. The mean total WS score was 3.92 (SD 1.86) in the EOS group, significantly higher than the 2.59 (SD 1.79) in the LOS group. Minor physical anomalies are an indirect index for early prenatal central nervous system (CNS) maldevelopment; the present study indicated association between minor physical anomalies and EOS, thus a relationship between early prenatal CNS maldevelopment and EOS. These results support the hypothesis that EOS constitutes a subset of schizophrenia in which neurodevelopmental damage is largely involved.

Pathogenesis of schizophrenia: Part II. Temporo-frontal two-step hypothesis

The objective of the present study was to provide a pathophysiological model of the development of schizophrenia. The method used was the selective review of recent findings, including those of animal models from our own department, to clarify the relationship between morphological brain changes and dopamine metabolism, and the pathophysiology of schizophrenia. The results showed that entorhinal cortex-lesioned animals had increased concentrations of dopamine in the amygdala, and methamphetamine-induced dopamine release in the amygdala of lesioned rats was significantly enhanced compared with sham-operated rats. These results and the morphological findings in schizotypal disorder patients support the view that temporal lobe changes may underlie a vulnerability to schizophrenia. Latent dysfunction in these regions may become clinically apparent as positive psychotic symptoms due to additional frontal lobe changes in schizophrenia. For the emergence of positive Schneiderian symptoms, aberrant activity of sociality-related circuits, including the amygdala was postulated. In conclusion, a temporo-frontal two-step hypothesis for the development of schizophrenia was suggested.

Oxidative damage and schizophrenia: an overview of the evidence and its therapeutic implications

Free radicals are highly reactive chemical species generated during normal metabolic processes. which in excess can lead to membrane damage. Elaborate antioxidant defence systems exist to protect against oxidative stress. There is accumulating evidence of altered antioxidant capacity in schizophrenia. Membrane dysfunction can be secondary to free radical-mediated pathology, and may contribute to specific aspects of schizophrenic symptomatology and complications of its treatment. Specifically, free radical-mediated abnormalities may contribute to the development of a number of clinically significant consequences, including prominent negative symptoms, tardive dyskinesia, neurological 'soft' signs and parkinsonian symptoms. Our previous results showing altered membrane dynamics and antioxidant enzyme activities in schizophrenia, and findings from other investigators, are consistent with the notion of free radical-mediated neurotoxicity in schizophrenia. These findings provide a theoretical basis from which the development of novel therapeutic strategies such as fatty acid and antioxidant supplementation can occur in the future.

Obstetric complications and schizophrenia: prenatal underdevelopment and subsequent neurodevelopmental impairment

BACKGROUND

Many studies have shown an association between obstetric complications and schizophrenia.

AIMS

To investigate the possible relationship between prenatal underdevelopment, neurodevelopmental abnormality and subsequent schizophrenia.

METHOD

The literature was reviewed. In particular, by pooling data from recently published reports, we examined whether low birthweight (< 2500 g) is a risk factor for schizophrenia.

RESULTS

Low birthweight was significantly more common for subjects with schizophrenia than for control subjects: P < 0.00001, odds ratio 2.6 (95% CI 2.0 to 3.3). Individuals born prematurely are at greater risk of perinatal brain damage and subsequent neurodevelopmental abnormalities, which may constitute vulnerability to the development of schizophrenia. Patients with schizophrenia who had low birthweights also tended to have poor premorbid psychosocial adjustment.

CONCLUSIONS

Low birthweight is a modest, but definite, risk factor for schizophrenia. Brain damage associated with prenatal underdevelopment has a role in the pathogenesis of poor premorbid functioning and subsequent neurodevelopmental impairment in some cases of schizophrenia.

Effects of nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester on phencyclidine-induced effects in rats

Phencyclidine (PCP) is widely used as an animal model of schizophrenia. In rats, acute PCP treatment increased locomotor activity and induced stereotyped behaviours consisting of head weaving, turning and backpedalling. PCP had differential regional effects on c-fos expression in rat brain, suggesting different patterns of neuronal activity. The most prominent immunostaining was observed in the cortical regions. To elucidate the role of nitric oxide, an important intracellular messenger, in the mechanism of action of PCP the effects of nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) were studied in PCP-treated animals. L-NAME potentiated PCP-induced behaviours and c-fos expression in many brain regions. The greatest increases were observed in the frontal, retrosplenial granular cortex, cerebellum, thalamic and subthalamic nuclei. While PCP alone induced low c-fos expression in the entorhinal cortex, with almost no expression in the rostral part of caudate putamen, animals pretreated with L-NAME showed marked activation in these brain areas. These results strongly indicate the involvement of the nitric oxide system in the mechanism of action of PCP.

Postmortem studies in schizophrenia

For over a century, postmortem studies have played a central part in the search for the structural and biochemical pathology of schizophrenia. However, for most of this time, little progress has been made. Recently, the situation has begun to change, helped by the emergence of more powerful methodologies and research designs, and by the availability of brain imaging to provide complementary information. As a result, it can now be clearly concluded that there are structural cerebral abnormalities in schizophrenia that are intrinsic to the disorder. The neuropathological process is not primarily degenerative, but involves a change in the normal cytoarchitecture of the brain, probably originating in development. Neurochemically, there is postmortem evidence for alterations in several transmitter systems including dopamine, glutamate, serotonin, and γ-aminobutyric acid (GABA). The cardinal findings are reviewed here, together with a consideration of the conceptual and methodological issues that face postmortem studies of schizophrenia.

The pharmacology of latent inhibition as an animal model of schizophrenia

The nature of the primary symptoms of schizophrenia and our lack of knowledge of its underlying cause both contribute to the difficulty of generating convincing animal models of schizophrenia. A more recent approach to investigating the biological basis of schizophrenia has been to use information processing models of the disease to link psychotic phenomena to their neural basis. Schizophrenics are impaired in a number of experimental cognitive tasks that support this approach, including sensory gating tasks and models of selective attention such as latent inhibition (LI). LI refers to a process in which noncontingent presentation of a stimulus attenuates its ability to enter into subsequent associations, and it has received much attention because it is widely considered to relate to the cognitive abnormalities that characterise acute schizophrenia. Several claims have been made for LI having face and construct validity for schizophrenia. In this review of the pharmacological studies carried out with LI we examine its claim to predictive validity and the role of methodological considerations in drug effects. The data reviewed demonstrate that facilitation of low levels of LI is strongly related to demonstrated antipsychotic activity in man and all major antipsychotic drugs, both typical and atypical, have been shown to potentiate LI using a variety of protocols. Very few compounds without antipsychotic activity are active in this model. In contrast, disruption of LI occurs with a wide range of drugs and the relationship with psychotomimetic potential is less clear. Although reversal of disrupted LI has also been used as a model for antipsychotic acticity, mostly using amphetamine-induced disruption, insufficient studies have been carried out to evaluate its claim to predictive validity. However, like facilitation, it is sensitive to both typical and atypical antipsychotic agents. The data we have reviewed here demonstrate that facilitation of LI and, perhaps to a lesser extent, reversal of disrupted LI fulfil the criteria for predictive validity.

Neonatal lesions of the left entorhinal cortex affect dopamine metabolism in the rat brain

The present study was performed to determine the effects of neonatal excitotoxic lesions of the left entorhinal cortex on dopamine (DA) metabolism and release in limbic regions of the rat brain. Quinolinic acid or phosphate buffered saline was infused into the left entorhinal cortex of rat pups on postnatal day 7 (PD7). Concentrations of DA,3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the lateral amygdala, nucleus accumbens, caudate-putamen, and medial prefrontal cortex were determined in the postmortem brains of lesioned and sham-operated rats on PD35 and PD56. On PD35, concentrations of DA in the bilateral lateral amygdala and HVA in the left lateral amygdala were significantly increased in lesioned rats compared with sham-operated animals, while no significant change was observed in the other three brain areas. On PD56, in addition to the increased concentration of DA in the left lateral amygdala, those of DA, DOPAC and HVA in the caudate-putamen, and DA in the nucleus accumbens were found to be increased, but DA concentrations in the right medial prefrontal cortex were decreased. The DOPAC/DA concentration ratio was, however, decreased in the amygdala and nucleus accumbens of the lesioned rats. In an in vivo microdialysis study, methamphetamine (MAP: 2 mg/kg, i.p.)-induced DA release in the amygdala of lesioned rats was significantly enhanced compared with sham-operated rats on both PD35 and PD56. There were no significant differences in MAP-induced DA release in the caudate-putamen between the sham-operated and lesioned rats at any time point. These findings provide evidence that neonatally induced structural abnormalities in the entorhinal cortex affect DA transmission in the limbic regions at the adolescent stage.

Chronic prenatal exposure to carbon monoxide results in a reduction in tyrosine hydroxylase-immunoreactivity and an increase in choline acetyltransferase-immunoreactivity in the fetal medulla: implications for Sudden Infant Death Syndrome

Maternal cigarette smoking during pregnancy is associated with a significantly increased risk of Sudden Infant Death Syndrome (SIDS). This study investigated the effects of prenatal exposure to carbon monoxide (CO), a major component of cigarette smoke, on the neuroglial and neurochemical development of the medulla in the fetal guinea pig. Pregnant guinea pigs were exposed to 200 p.p.m CO for 10 h per day from day 23-25 of gestation (term = 68 days) until day 61-63, at which time fetuses were removed and brains collected for analysis. Using immunohistochemistry and quantitative image analysis, examination of the medulla of CO-exposed fetuses revealed a significant decrease in tyrosine hydroxylase-immunoreactivity (TH-IR) in the nucleus tractus solitarius, dorsal motor nucleus of the vagus (DMV), area postrema, intermediate reticular nucleus, and the ventrolateral medulla (VLM), and a significant increase in choline acetyltransferase-immunoreactivity (ChAT-IR) in the DMV and hypoglossal nucleus compared with controls. There was no difference between groups in immunoreactivity for the m2 muscarinic acetylcholine receptor, substance P- or met-enkephalin in any of the medullary nuclei examined, nor was there evidence of reactive astrogliosis. The results show that prenatal exposure to CO affects cholinergic and catecholaminergic pathways in the medulla of the guinea pig fetus, particularly in cardiorespiratory centers, regions thought to be compromised in SIDS.

Possible implications of the dopamine D(3) receptor in schizophrenia and in antipsychotic drug actions

The D(3) receptor may represent an important target for antipsychotic drugs which all bind with high affinity and do not induce upon repeated administration either tolerance or receptor upregulation. The D(3) receptor is localized in brain areas, namely the nucleus accumbens and cerebral cortex, implicated in neural circuits believed to display defective functioning in schizophrenia. Overexpression of the D(3) receptor, which accounts for the behavioral sensitization to levodopa in a rodent model of Parkinson's disease, might also be responsible for the sensitization to dopamine agonists observed in schizophrenia. The appearance of the D(3) receptor during brain development, early in proliferating neuroepithelia and later in neurons from limbic areas, suggests further studies to assess its participation in the neurodevelopmental disorders of schizophrenia. Finally, meta-analysis of approximately 30 studies comprising over 2500 patients indicate that a polymorphism in the coding sequence of the D(3) receptor is associated with a small but significant enhancement of vulnerability to the disease.

Changes in limbic dopamine metabolism following quinolinic acid lesions of the left entorhinal cortex in rats

To examine the effects of lesions of the entorhinal cortex on limbic dopamine (DA) metabolism, DA and its metabolites were assayed in five brain regions (the medial prefrontal cortex, anterior cingulate cortex, caudate-putamen, accumbens nucleus, and lateral amygdala), 14 and 28 days after quinolinic acid or sham lesions of the left entorhinal cortex in rats. Concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) on day 14 in the medial prefrontal cortex, accumbens nucleus, and lateral amygdala of the entorhinal cortex lesioned animals were significantly decreased compared with the controls, but they returned to control levels on day 28. The concentration of DA in the lateral amygdala and spontaneous locomotion to a novel environment were significantly increased on day 28 after the lesion. These results suggest that entorhinal cortex lesions alter mesolimbic dopamine metabolism, particularly in the amygdala.

Morphological changes in neuropeptide Y-positive fiber in the hippocampal formation of schizophrenics

1. The authors observed NPY-positive fibers in the CA4 area of the hippocampus from schizophrenics and normal controls using immunohistochemical techniques. 2. Positive fibers followed a straight course and were oriented to exit the CA4 region of hippocampus in normal controls. 3. Many NPY-positive fibers in the CA4 area appeared coiled or helix-like or appeared wasted and thread-like in schizophrenic brains, compared to those of normal controls. 4. These findings may indicate a dysfunction of the interneuron in the schizophrenic brain and support the hypothesis of developmental impairments of the CNS in schizophrenia, and these morphological changes in fibers may relate to schizophrenic symptoms such as memory or/and learning deterioration.

Interruptions of early cortical development affect limbic association areas and social behaviour in rats; possible relevance for neurodevelopmental disorders

Deficits in social behaviour are found in several neuropsychiatric disorders with a presumed developmental origin. Adequate social behaviour may rely importantly on the associative integration of new stimuli with previously stored, related information. The limbic allocortex, in particular the entorhinal region, is thought to support this kind of processing. Therefore, in the present study, gestating dams were treated with methylazoxymethanol acetate (MAM) on one of gestational days nine to twelve, to interrupt neuronal proliferation in the entorhinal region of the developing foetuses. Effects of prenatal MAM administration on social behaviour were evaluated in adult animals. As the entorhinal cortex has been implicated by some studies in spatial memory, effects on this function were also investigated. Following the behavioural studies, brain morphology was screened for effects of MAM. Our results show moderate to severe social impairment in MAM-treated animals, depending on the exact timing of prenatal exposure. By contrast, spatial reference and working memory were not importantly affected in any group. Analysis of brain morphology in the MAM-treated offspring supported maldevelopment of the entorhinal cortex and revealed mild abnormalities also in some connected limbic and limbic affiliated structures, such as the perirhinal and ectorhinal cortex, the anterior cingulate cortex and the medial septum-diagonal band region. Findings are discussed with respect to entorhinal cortex function, and with regard to their relevance for psychiatric disorders with a putatively neurodevelopmental pathogenesis, such as schizophrenia.

Increased expression of Wnt-1 in schizophrenic brains

The regulated expression of Wnt-1, one member of the wingless/Wnt pathway, in the brain is critical for many neurodevelopmental processes. Recently, it has been reported that the wingless/Wnt pathway participates in a complex behavioral phenomenon and suggested that this pathway's molecules are candidate genes for neuropsychiatric disorders. Thus, we investigated the expression of Wnt-1 in the hippocampal region, which is believed to be closely involved in the pathophysiology of schizophrenia, of postmortem brains from 10 schizophrenic and 10 control individuals. Immunohistochemical analysis with polyclonal antibodies recognizing Wnt-1 revealed immunoreactivity primarily in the pyramidal cell layer, particularly in CA3 and CA4 regions. We observed a significant elevation in the number of Wnt-1-immunoreactive neurons in the great majority of schizophrenic brains relative to that in controls. The expression of Wnt-1 may be related to cell adhesion, synaptic rearrangement, and plasticity. Therefore, the increase in Wnt-1 immunoreactivity in schizophrenic hippocampi suggests an altered plasticity of this structure in a large proportion of schizophrenic brains. These findings suggest an abnormality of the wingless/Wnt pathway present in the schizophrenic brain and may support the 'neurodevelopmental hypothesis' of schizophrenia.

Schizophrenia and the influenza epidemics of 1957 in Japan

BACKGROUND

We tested the hypothesis that the exposure to an influenza epidemic during the second trimester of gestation is associated with an increased risk of later development of schizophrenia.

METHODS

There were three influenza epidemics (A/B mixed type, the first A2 type and the second A2 type) in 1957 in Kochi, Japan. We compared the risk of developing schizophrenia in birth cohorts exposed to these three influenza epidemics during gestation with that in birth cohorts not exposed. To identify subjects who had developed schizophrenia, we surveyed patients with schizophrenia who received medical care at all psychiatric institutions in Kochi prefecture.

RESULTS

There is a pattern that schizophrenic births increase twice or more among female subjects who were exposed to each of three influenza epidemics in the fifth month of gestation. The increase in the female births exposed to the second A2 epidemic was significant (relative risk 2.86, 95% confidence interval 1.37-5.26). This pattern across the three epidemics was not observed in male subjects.

CONCLUSIONS

Prenatal exposure to an influenza epidemic during the second trimester increased the risk of later development of schizophrenia in female births.

The neuropathology of schizophrenia. A critical review of the data and their interpretation

Despite a hundred years' research, the neuropathology of schizophrenia remains obscure. However, neither can the null hypothesis be sustained--that it is a 'functional' psychosis, a disorder with no structural basis. A number of abnormalities have been identified and confirmed by meta-analysis, including ventricular enlargement and decreased cerebral (cortical and hippocampal) volume. These are characteristic of schizophrenia as a whole, rather than being restricted to a subtype, and are present in first-episode, unmedicated patients. There is considerable evidence for preferential involvement of the temporal lobe and moderate evidence for an alteration in normal cerebral asymmetries. There are several candidates for the histological and molecular correlates of the macroscopic features. The probable proximal explanation for decreased cortical volume is reduced neuropil and neuronal size, rather than a loss of neurons. These morphometric changes are in turn suggestive of alterations in synaptic, dendritic and axonal organization, a view supported by immunocytochemical and ultrastructural findings. Pathology in subcortical structures is not well established, apart from dorsal thalamic nuclei, which are smaller and contain fewer neurons. Other cytoarchitectural features of schizophrenia which are often discussed, notably entorhinal cortex heterotopias and hippocampal neuronal disarray, remain to be confirmed. The phenotype of the affected neuronal and synaptic populations is uncertain. A case can be made for impairment of hippocampal and corticocortical excitatory pathways, but in general the relationship between neurochemical findings (which centre upon dopamine, 5-hydroxytryptamine, glutamate and GABA systems) and the neuropathology of schizophrenia is unclear. Gliosis is not an intrinsic feature; its absence supports, but does not prove, the prevailing hypothesis that schizophrenia is a disorder of prenatal neurodevelopment. The cognitive impairment which frequently accompanies schizophrenia is not due to Alzheimer's disease or any other recognized neurodegenerative disorder. Its basis is unknown. Functional imaging data indicate that the pathophysiology of schizophrenia reflects aberrant activity in, and integration of, the components of distributed circuits involving the prefrontal cortex, hippocampus and certain subcortical structures. It is hypothesized that the neuropathological features represent the anatomical substrate of these functional abnormalities in neural connectivity. Investigation of this proposal is a goal of current neuropathological studies, which must also seek (i) to establish which of the recent histological findings are robust and cardinal, and (ii) to define the relationship of the pathological phenotype with the clinical syndrome, its neurochemistry and its pathogenesis.

Conceptual foundations of schizophrenia: I. Degeneration

OBJECTIVE

This is the first of two papers that aim to identify some of the institutional processes of 19th century European psychiatry, and some prevailing cultural themes of that era that played a role in shaping the development of schizophrenia as a disease concept.

METHOD

Three areas of psychiatric history are examined: the first is concerned with the key figures who coined the concept of dementia praecox; the second with the rise of the asylum; and the third is to do with the ideology of 19th century psychiatric science and its relationship to a broader intellectual milieu. These three literatures are examined for common themes.

RESULTS

The theme of degeneration is evident in all three literatures, and denotes both a biological process (neuro-degeneration) and a moral state (degeneracy).

CONCLUSIONS

The idea of degeneration, a pervasive cultural theme of the 19th century, dominated psychiatric thinking long before schizophrenia was developed as a diagnostic category. It contributed to the ideational form-work that gave foundation, structure and shape to the concept of schizophrenia.

Expression of Fos protein in the limbic regions of the rat following haloperidol decanoate

To identify sites of antipsychotic drug action, the effects of acute and chronic haloperidol treatment on Fos protein expression in rat brain regions were examined by immunohistochemical methods. Male Wistar rats were injected with haloperidol decanoate (40 mg/kg, i.m. ) or vehicle. Fourteen days after injection, each rat was given an acute subcutaneous injection of haloperidol (0.25 mg/kg) or vehicle, and was transcardially perfused 2 h after the second injection. A single dose of haloperidol to chronic vehicle-treated rats produced significant increases in Fos-positive neurons in 18 of 21 brain regions examined including the several cortical areas, caudate-putamen, nucleus accumbens, lateral septum, thalamic nuclei, amygdala, hippocampus CA1, mesencephalic dopaminergic nuclei, and periaqueductal grey. The rats treated with acute vehicle after chronic haloperidol showed persistent Fos increases in confined brain regions comprising the lateral and central amygdala, lateral septum, and entorhinal cortex. Additional haloperidol injection to the chronic haloperidol-treated rats induced significant increases in Fos immunoreactivity in more widespread limbic-thalamo-cortical areas, whereas no significant increase was seen in the dorsolateral caudate-putamen. The persisting effects of haloperidol in the limbic and related structures, especially the amygdala, lateral septum, and entorhinal area may be of significance to the efficacy of long-term haloperidol treatment.

Methylazoxymethanol acetate-induced abnormalities in the entorhinal cortex of the rat; parallels with morphological findings in schizophrenia

It has been suggested repeatedly that the non-heritable factors in the pathogenesis of schizophrenia involve abnormalities of prenatal neurodevelopment. Furthermore, post-mortem studies show neuropathology of apparently developmental origin in the entorhinal cortex and other brain regions of schizophrenic subjects. In an attempt to model a developmental defect of the entorhinal region in the rat, cerebrocortical proliferation was briefly interrupted during its earliest stages, when the entorhinal area is thought to undergo major cell division. Specifically, the experimental set-up involved the administration of methylazoxymethanol acetate (MAM) on 1 of 4 consecutive days of embryonal development, from E9 to E12. Analysis of the forebrain in adult animals shows reduction of the entorhinal cortex in rats treated on each of these days. This effect shifts from lateral to medial divisions of the entorhinal cortex with later administration of MAM, following a known developmental gradient. Morphological consequences of MAM administration appear to be largely confined to the entorhinal cortex in the groups treated on E9 to E11, although slight reductions of the frontal and occipital neocortex were also observed in these animals. MAM treatment on E12 produces relatively more widespread damage, as reflected among other in a small reduction of brain weight. The described brain abnormalities are not accompanied by obvious phenotypical changes in any, but the E12-treated group. They, moreover, involve cortical thinning, disorganised cortical layering, and abnormal temporal asymmetries. These finding bare some similarity to observations in brains of schizophrenic subjects. The possible relevance of this approach in modeling neurodevelopmental aspects of schizophrenia is discussed.

The role of glycoproteins in neural development function, and disease

Glycoproteins play key roles in the development, structuring, and subsequent functioning of the nervous system. However, the complex glycosylation process is a critical component in the biosynthesis of CNS glycoproteins that may be susceptible to the actions of toxicological agents or may be altered by genetic defects. This review will provide an outline of the complexity of this glycosylation process and of some of the key neural glycoproteins that play particular roles in neural development and in synaptic plasticity in the mature CNS. Finally, the potential of glycoproteins as targets for CNS disorders will be discussed.

Asymmetrical increases in dopamine turn-over in the nucleus accumbens and lack of changes in locomotor responses following unilateral dopaminergic depletions in the entorhinal cortex

Functional interdependence between mesencephalic dopaminergic pathways is an emerging concept. Using in vivo voltammetry and acute manipulation of dopaminergic transmission with pharmacological agents, we have previously reported the existence of a preferentially left lateralized functional interdependence between the entorhinal cortex and the nucleus accumbens. The aim of the present work was to test if this phenomenon is only a dynamic process or if compensation occurs when interdependent functioning is considered in a more long-term perspective. In this study 6-OHDA lesions of the dopamine terminals of the entorhinal cortex were performed separately in the left and right hemispheres. Spontaneous and (+)-amphetamine stimulated locomotor activity were recorded 3 weeks after unilateral interventions in the Ent. Variations in DA and DOPAC levels were measured in the nucleus accumbens 5 weeks after the lesion. The following results were obtained. After unilateral 6-OHDA in the left Ent, DA and DOPAC tissue contents as well as the DOPAC/DA ratio were found significantly changed in nucleus accumbens in the two hemispheres. After dopaminergic destruction in the right Ent only the DOPAC/DA ratio in the left Acc was found statistically elevated. No differences in spontaneous or (+)-amphetamine-stimulated locomotor activity were observed after either left or right lesions. These data confirm those previously obtained with the voltammetric approach and further support the existence of an asymmetrical functional interdependence between mesencephalic DAergic pathways reaching the Ent and the Acc. These results may provide new insights in the pathophysiology of schizophrenic psychoses.

Progress in research into the neurobiological bases of schizophrenia: A review and commentary

Schizophrenia is a severe, often disabling, and sometimes enduring psychiatric disorder. Ever since its characterisation as a mental illness at the beginning of this century, its nature, course and aetiology have been the subject of debate. As understanding of genetic mechanisms, brain biochemistry, and the relationship between brain structure and function has recently developed, researchers are now making considerable progress in their attempts to unravel some of the neurobiological factors of importance in the development, manifestation, and treatment of schizophrenia.

Current research in three main areas of interest is described in this review paper. Findings from genetic research suggest that, in many cases, schizophrenia may have a neurodevelopmental origin, which is, in turn, influenced by genetic factors. Biochemical research indicates that disturbances to the functioning of several brain neurotransmitters may collectively contribute to the changes in behaviour that are identified as the signs and symptoms of the condition. Neuropsychological research reinforces the view that schizophrenia is not a unitary condition, and that disturbances to discrete networks of neurons may be responsible for different sub-types of the disorder.