Prefrontal Cortex Of Schizophrenics Research Articles

EZH1 is an antipsychotic-sensitive epigenetic modulator of social and motivational behavior that is dysregulated in schizophrenia

BackgroundWith the capacity to modulate gene networks in an environmentally-sensitive manner, the role of epigenetic systems in mental disorders has come under intense investigation. Dysregulation of epigenetic effectors, including microRNAs and histone-modifying enzymes, may better explain the role of environmental risk factors and the observed heritability rate that cannot be fully attributed to known genetic risk alleles. Here, we aimed to identify novel epigenetic targets of the schizophrenia-associated microRNA 132 (miR-132). MethodsHistone modifications were quantified by immunodetection in response to viral-mediated overexpression of miR-132 while a luminescent reporter system was used to validate targets of miR-132 in vitro. Genome-wide profiling, quantitative PCR and NanoSting were used to quantify gene expression in post-mortem human brains, neuronal cultures and prefrontal cortex (PFC) of mice chronically exposed to antipsychotics. Following viral-mediated depletion of Enhancer of Zeste 1 (EZH1) in the murine PFC, behaviors including sociability and motivation were assessed using a 3-chambered apparatus and forced-swim test, respectively. ResultsOverexpression of miR-132 decreased global histone 3 lysine 27 tri-methylation (H3K27me3), a repressive epigenetic mark. Moreover, the polycomb-associated H3K27 methyltransferase, EZH1, is regulated by miR-132 and upregulated in the PFC of schizophrenics. Unlike its homolog EZH2, expression of EZH1 in the murine PFC decreased following chronic exposure to antipsychotics. Viral-mediated depletion of EZH1 in the mouse PFC attenuated sociability, enhanced motivational behaviors, and affected gene expression pathways related to neurotransmission and behavioral phenotypes. ConclusionsEZH1 is dysregulated in schizophrenia, sensitive to antipsychotic medications, and a brain-enriched miR-132 target that controls neurobehavioral phenotypes.

PKA activation and endothelial claudin-5 breakdown in the schizophrenic prefrontal cortex.

Schizophrenia is thought to be caused by a combination of genetic and environmental factors; however, its pathogenesis remains largely unknown. Here, we focus on the endothelial tight-junction protein claudin-5 (CLDN5), because the CLDN5 gene is mapped to the schizophrenia-associated 22q11.2 deletion region, and a single nucleotide polymorphism in the CLDN5 locus is also linked to schizophrenia. We show, by RT-qPCR and immunohistochemistry, that the expressions of CLDN5 mRNA and protein are significantly increased and decreased, respectively, in the schizophrenic prefrontal cortex (PFC) compared with control PFC. These changes were not observed in the schizophrenic visual cortex (VC), and neither the density nor diameter of the CD34-positive microvessels was altered in the schizophrenic PFC or VC. Interestingly, protein kinase A (PKA) was activated in the microvascular and perivascular regions of the schizophrenic PFC, and the pPKA-positive microvascular endothelial cells occasionally exhibited focal loss of CLND5. Since we previously demonstrated that cAMP induced CLDN5 mRNA expression and size-selective loosening of the endothelial barrier in PKA-independent and -dependent manners, respectively, a similar mechanism could contribute to the discrepancy between mRNA and protein expression of CLDN5 in the schizophrenic PFC. Taken collectively, these findings provide novel insights into the pathophysiology of schizophrenia.

Transcriptomic evidence for immaturity of the prefrontal cortex in patients with schizophrenia.

BackgroundSchizophrenia, a severe psychiatric disorder, has a lifetime prevalence of 1%. The exact mechanisms underlying this disorder remain unknown, though theories abound. Recent studies suggest that particular cell types and biological processes in the schizophrenic cortex have a pseudo-immature status in which the molecular properties partially resemble those in the normal immature brain. However, genome-wide gene expression patterns in the brains of patients with schizophrenia and those of normal infants have not been directly compared. Here, we show that the gene expression patterns in the schizophrenic prefrontal cortex (PFC) resemble those in the juvenile PFC.ResultsWe conducted a gene expression meta-analysis in which, using microarray data derived from different studies, altered expression patterns in the dorsolateral PFC (DLFC) of patients with schizophrenia were compared with those in the DLFC of developing normal human brains, revealing a striking similarity. The results were replicated in a second DLFC data set and a medial PFC (MFC) data set. We also found that about half of the genes representing the transcriptomic immaturity of the schizophrenic PFC were developmentally regulated in fast-spiking interneurons, astrocytes, and oligodendrocytes. Furthermore, to test whether medications, which often confound the results of postmortem analyses, affect on the juvenile-like gene expressions in the schizophrenic PFC, we compared the gene expression patterns showing transcriptomic immaturity in the schizophrenic PFC with those in the PFC of rodents treated with antipsychotic drugs. The results showed no apparent similarities between the two conditions, suggesting that the juvenile-like gene expression patterns observed in the schizophrenic PFC could not be accounted for by medication effects. Moreover, the developing human PFC showed a gene expression pattern similar to that of the PFC of naive Schnurri-2 knockout mice, an animal model of schizophrenia with good face and construct validity. This result also supports the idea that the transcriptomic immaturity of the schizophrenic PFC is not due to medication effects.ConclusionsCollectively, our results provide evidence that pseudo-immaturity of the PFC resembling juvenile PFC may be an endophenotype of schizophrenia.

Lack of effects of typical and atypical antipsychotics in DARPP-32 and NCS-1 levels in PC12 cells overexpressing NCS-1

BackgroundSchizophrenia is the major psychiatry disorder, which the exact cause remains unknown. However, it is well known that dopamine-mediated neurotransmission imbalance is associated with this pathology and the main target of antipsychotics is the dopamine receptor D2. Recently, it was described alteration in levels of two dopamine signaling related proteins in schizophrenic prefrontal cortex (PFC): Neuronal Calcium Sensor-1 (NCS-1) and DARPP-32. NCS-1, which is upregulated in PFC of schizophrenics, inhibits D2 internalization. DARPP-32, which is decreased in PFC of schizophrenics, is a key downstream effector in transducing dopamine signaling. We previously demonstrated that antipsychotics do not change levels of both proteins in rat's brain. However, since NCS-1 and DARPP-32 levels are not altered in wild type rats, we treated wild type PC12 cells (PC12 WT) and PC12 cells stably overexpressing NCS-1 (PC12 Clone) with antipsychotics to investigate if NCS-1 upregulation modulates DARPP-32 expression in response to antipsychotics treatment.ResultsWe chronically treated both PC12 WT and PC12 Clone cells with typical (Haloperidol) or atypical (Clozapine and Risperidone) antipsychotics for 14 days. Using western blot technique we observed that there is no change in NCS-1 and DARPP-32 protein levels in both PC12 WT and PC12 Clone cells after typical and atypical antipsychotic treatments.ConclusionsBecause we observed no alteration in NCS-1 and DARPP-32 levels in both PC12 WT and Clone cells treated with typical or atypical antipsychotics, we suggest that the alteration in levels of both proteins in schizophrenic's PFC is related to psychopathology but not with antipsychotic treatment.

Involvement of SMARCA2/BRM in the SWI/SNF chromatin-remodeling complex in schizophrenia

Chromatin remodeling may play a role in the neurobiology of schizophrenia and the process, therefore, may be considered as a therapeutic target. The SMARCA2 gene encodes BRM in the SWI/SNF chromatin-remodeling complex, and associations of single nucleotide polymorphisms (SNPs) to schizophrenia were found in two linkage disequilibrium blocks in the SMARCA2 gene after screening of 11 883 SNPs (rs2296212; overall allelic P = 5.8 x 10(-5)) and subsequent screening of 22 genes involved in chromatin remodeling (rs3793490; overall allelic P = 2.0 x 10(-6)) in a Japanese population. A risk allele of a missense polymorphism (rs2296212) induced a lower nuclear localization efficiency of BRM, and risk alleles of intronic polymorphisms (rs3763627 and rs3793490) were associated with low SMARCA2 expression levels in the postmortem prefrontal cortex. A significant correlation in the fold changes of gene expression from schizophrenic prefrontal cortex (from the Stanley Medical Research Institute online genomics database) was seen with suppression of SMARCA2 in transfected human cells by specific siRNA, and of orthologous genes in the prefrontal cortex of Smarca2 knockout mice. Smarca2 knockout mice showed impaired social interaction and prepulse inhibition. Psychotogenic drugs lowered Smarca2 expression while antipsychotic drugs increased it in the mouse brain. These findings support the existence of a role for BRM in the pathophysiology of schizophrenia.

Evidence of altered calmodulin immunoreactivity in areas 9 and 32 of schizophrenic prefrontal cortex

Schizophrenia is a severe neuropsychiatric disorder. Previous studies have implicated the prefrontal cortex (PFC) [Harrison PJ. The neuropathology of schizophrenia a critical review of the data and their interpretation. Brain 1999;122:593–624; Jones LB. Recent cytoarchitectonic changes in the prefrontal cortex of schizophrenics. Frontiers of Bioscience 2001;6:E148–53]. Recent immunocytochemical studies have shown a dramatic decrease in MAP2 and neurogranin [Jones L, Johnson N, Byne W. Alterations in MAP2 staining in area 9 and 32 of schizophrenic prefrontal cortex. Psychiatry Research 2002;114:137–48; Broadbelt K, Pamprasaud A, Jones LB. Evidence of altered neurogranin immunoreactivity in areas 9 and 32 of schizophrenic prefrontal cortex. Schizophrenia Research 2006;87:6–14] a loss of either is suggestive of dendritic lesions [Li GL, Farooque M, Lewen A., Lennmyr F, Holtz A., Olsson Y. MAP2 and neurogranin as markers for dendritic lesions in cns injury an immunohistochemical study in the rat. APMIS 2002;108:98–106.]. Neurogranin is an upstream regulator of calcium and calmodulin [Prichard L, Deloulmes JC, Storm DR. Interactions between Neurogranin and Calmodulin in vivo. Journal of Biological Chemistry 1999;274:7689–94]. A direct action of this pathway is the phosphorylation of MAP2, which is required for microtubule stabilization. Because of the above findings as well as moropholigical alterations [Broadbelt K, Byne W, Jones LB. Evidence for a decrease in primary and secondary basilar dendrites on pyramidal cells in area 32 of schizophrenic prefrontal cortex. Schizophrenia Research 2002;58:75–81] we examined the expression of the active form of calmodulin in layers III and V of areas 9 and 32 in six controls and six schizophrenics matched for age, sex, and postmortem interval. Using area fraction analysis we quantified immunostaining and counted the number of immunopositive pyramidal cells and interneurons as well as immunonegative pyramidal cells. Area fraction analysis showed a significant decrease in immunostaining in area nine layers III (58%) and V (44%), area 32 layers III (51%) and V (32%). We found a significant reduction in the density of immunopositive pyramidal cells in area 9 (11%) layer III, (20%) layer V, area 32 (16%) layer III and (17%) layer V with no difference in immunopositive interneurons. These data suggest a loss of the active form of calmodulin with pyramidal cells being preferentially affected suggesting that the calcium calmodulin dependent pathway may be altered in the pyramidal cells in the PFC.

Schizophrenia: more evidence for less glutamate

Evaluation of: Hahn CJ, Hoau-Yan W, Dan-Sung C et al. Altered neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in schizophrenia. Nat. Med. 12, 824–828 (2006) [1].Schizophrenia may be associated with deficits in glutamate transmission at the N-methyl-d-aspartate (NMDA) receptor complex. Recent work has shown that neuregulin 1 (NRG1) acts via ErbB4 receptors to inhibit NMDA receptor currents. This is important given that NRG1 is a convincing susceptibility gene in schizophrenia. Hahn and colleagues add to our knowledge of NRG1 modulation of NMDA receptors and show intriguing differences between control and schizophrenic brains. NMDA receptors in the schizophrenic prefrontal cortex showed smaller responses to exogenously applied NMDA/glycine. Furthermore, NMDA receptors in tissue from schizophrenic patients appeared to be more sensitive to the inhibitory effects of a fixed dose of NRG1. In agreement, the ErbB4–PSD-95–NMDA complex was more tightly coupled in schizophrenic brains and NRG1-mediated stimulation of ErbB4 was markedly enhanced. These findings underscore the importance of NMDA receptors in schizophrenia and support therapeutic strategies aimed at boosting glutamate transmission.

Evidence of altered neurogranin immunoreactivity in areas 9 and 32 of schizophrenic prefrontal cortex

Schizophrenia is a complex and poorly understood neuropsychiatric disorder. Much research has begun to implicate the prefrontal cortex in the disease. Using immunocytochemistry we determined if neurogranin, a protein found in dendrites, spines and cell bodies and an upstream regulator of calcium was altered in areas 9 and 32 of schizophrenic prefrontal cortex. We examined its expression in pyramidal cells in layers III and V. Tissues from 7 controls and 7 schizophrenics (from our original MAP2 study, Jones, L., Johnson, N., Byne, W., 2002. Alterations in MAP2 staining in area 9 and 32 of schizophrenic prefrontal cortex. Psych. Res. 114, 137–148) matched for age, sex and postmortem interval were examined. Using area fraction analysis we quantified the immunostaining. Additionally, we counted the number of positively stained pyramidal cells in the same 7 pairs. Neurogranin immunostaining was dramatically reduced in both layers III (72%) and V (50%) in area 9. In area 32 there was a more modest reduction in both layers III (36%) and V (40%). There was no difference in either brain region or layer in the density of positively stained pyramidal cells. These data confirm mounting evidence suggesting dendritic loss in the prefrontal cortex and suggest that the loss of protein does not appear to be due to a change in the number of cells producing the protein but rather in the amount of protein being produced. Additionally, these data suggest that the loss of neurogranin may alter the calcium–calmodulin dependent pathways due to its role as a regulator of calmodulin suggesting a link between structural and functional alterations of the pyramidal cells in the prefrontal cortex.

Dopamine receptor signaling molecules are altered in elderly schizophrenic cortex

Alterations of molecules that mediate dopaminergic signal transduction have been found in schizophrenia, supporting the hypothesis of altered dopaminergic neurotransmission in this illness. To further explore this hypothesis, the authors measured transcript expression of three proteins involved in dopamine (DA) signaling in postmortem dorsolateral prefrontal and anterior cingulate cortex of elderly schizophrenic subjects and a comparison group. The transcript encoding calcyon, a protein that potentiates crosstalk between D1 DA receptors and Gq/11-linked receptors, was increased in schizophrenic prefrontal and cingulate cortex by 25%. Transcript levels of spinophilin, a protein enriched in dendritic spines that modulates excitatory neurotransmission, were increased 22% in dorsolateral prefrontal cortex but were unchanged in anterior cingulate cortex in schizophrenia. Levels of DARPP-32 mRNA, a downstream effector of dopaminergic neurotransmission, were similar in both groups for both cortical groups. These alterations in spinophilin and calcyon mRNA levels in schizophrenic prefrontal and cingulate cortex provide further evidence of altered dopaminergic neurotransmission in this illness.

Human Dysbindin (DTNBP1) Gene Expression in Normal Brain and in Schizophrenic Prefrontal Cortex and Midbrain

Human Dysbindin (DTNBP1) Gene Expression in Normal Brain and in Schizophrenic Prefrontal Cortex and Midbrain

Stereological studies of capillary length density in the frontal cortex of schizophrenics

The presence of microvasculature abnormalities in the prefrontal cortex of schizophrenics was proposed in a recent study of molecular signatures of schizophrenia [Prabakaran et al (2004) Mol Psychiat 9:684-697]. To assess this possibility further, we investigated capillary length densities in prefrontal cortex area 9 and anterior cingulate cortex area 24 in postmortem brains from 13 schizophrenics and 13 age- and sex-matched controls. To check that our sample of brains shared cardinal neuropathological features of schizophrenia with previously reported case studies, we also measured cortical gray matter volumes and cortical thickness in areas 9 and 24. The mean cortical gray matter volume was significantly reduced in brains from schizophrenics compared to controls. Mean cortical thickness was significantly reduced in area 24, but not in area 9, in schizophrenics. There were no differences in mean capillary length densities in either area 9 or 24 between the two groups. Thus, alterations in capillary length density in the prefrontal cortex cannot be considered a general feature of schizophrenia. Compromised brain metabolism and occurrence of oxidative stress in the brain of schizophrenics are likely caused by other mechanisms.

Monoaminergic dysregulation in glutathione-deficient mice: Possible relevance to schizophrenia?

Several lines of research have implicated glutathione (GSH) in schizophrenia. For instance, GSH deficiency has been reported in the prefrontal cortex of schizophrenics in vivo. Further, in rats postnatal GSH-deficiency combined with hyperdopaminergia led to cognitive impairments in the adult. In the present report we studied the effects of 2-day GSH-deficiency with l-buthionine-( S, R)-sulfoximine on monoaminergic function in mice. The effect of GSH-deficiency per se and when combined with the amphetamine and phencyclidine (PCP) models of schizophrenia was investigated. GSH-deficiency significantly altered tissue levels of dopamine (DA), 5-hydroxytryptamine (5-HT) and their respective metabolites homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in a region-specific fashion. The effects of GSH-deficiency on tissue monoamines were distinct from and, generally, did not interact with the effects of amphetamine (5 #x00A0;mg/kg; i.p.) on tissue monoamines. Microdialysis studies showed that extracellular DA-release after amphetamine (5 #x00A0;mg/kg, i.p.) was two-fold increased in the nucleus accumbens of GSH-deficient mice as compared with control mice. Basal DA was unaltered. Further, extracellular levels of HVA in the frontal cortex and hippocampus and 5-HIAA in the nucleus accumbens were elevated by GSH-deficiency per se. Spontaneous locomotor activity in the open field was unchanged in GSH-deficient mice. In contrast, GSH-deficiency modulated the locomotor responses to mid-range doses of amphetamine (1.5 and 5 #x00A0;mg/kg, i.p.). Further, GSH-deficient mice displayed an increased locomotor response to low (2 and 3 #x00A0;mg/kg, i.p.) doses of phencyclidine (PCP). In conclusion, the data presented here show that even short-term GSH-deficiency has consequences for DA and 5-HT function. This was confirmed on both neurochemical and behavioral levels. How GSH and the monoamines interact needs further scrutiny. Moreover, the open field findings suggest reduced or altered N-methyl- d-aspartate (NMDA) receptor function in GSH-deficient mice. Thus, GSH-deficiency can lead to disturbances in DA, 5-HT and NMDA function, a finding that may have relevance for schizophrenia.

Increased expression of the astrocytic glutamate transporter GLT‐1 in the prefrontal cortex of schizophrenics

To verify whether altered glial glutamate uptake contributes to the reduced efficacy of glutamatergic transmission reported in the prefrontal cortex of schizophrenics, we studied the expression of GLT-1, the transporter responsible for most glutamate transport, in autoptic samples of prefrontal cortex using real time quantitative RT-PCR, immunocytochemistry, and functional assays. GLT-1 mRNA levels in medication-free patients were 2.5-fold higher than in controls, whereas they were normal or reduced in patients treated with antipsychotics. We also observed a 4-fold increase in L-[(3)H]-Glu uptake in Xenopus oocytes injected with mRNA from the prefrontal cortex of a medication-free schizophrenic and a 2-fold increase in GLT-1 protein in the same cortical area of another medication-free patient. Results suggest that GLT-1 mRNA, protein and function are increased in prefrontal cortex of schizophrenics.

Total length of nerve fibers in prefrontal and global white matter of chronic schizophrenics

It has been suggested that the dysfunction of the prefrontal cortex in schizophrenics is due to dysfunctional connections between the prefrontal cortex and more posterior structures. The present study uses a recent stereological method that allows quantitation of the myelinated nerve fibers in the brain white matter. As especially the prefrontal region is of interest in schizophrenics, the prefrontal white matter was quantitated separately. The total length of nerve fibers in post-mortem brains was estimated from eight male chronic schizophrenics and nine male controls (age-range: 40–81 years). Samples were taken systematically and randomly from both the entire white matter and selectively from the prefrontal white matter. The biopsies were rotated randomly before sectioning to avoid bias due to the anisotropic nature of nerve fibers. The fibers were counted at light microscopic level at about 10,000× magnification and the fiber diameter of each counted fiber was measured to get the size distribution of the fibers. The schizophrenics had a total of 129,000 km myelinated fibers in the white matter and 25,700 km in the prefrontal white matter, which was non-significantly different from a total of 137,000 km in the entire white matter and 27,600 km in the prefrontal white matter in controls. The size distribution of the fibers in schizophrenics was within normal limits compared to controls. Our results do not show a larger loss of nerve fibers in neither the white matter globally or in the prefrontal white matter of schizophrenics.

No genetic association between polymorphisms in the Fyn kinase gene and age of schizophrenic onset

Since the mRNA level of Fyn, a neurodevelopmental molecule, expression had been reported to be increased in postmortem schizophrenic prefrontal cortex and showed a strong correlation with age of disease onset, we investigated whether the three polymorphisms of the Fyn gene on genomic DNA (−93A/G, IVS10+37T/C and Ex12+894T/G) also had an effect on clinical onset in 139 unrelated schizophrenics. A comparison of the age of onset among the groups classified by polymorphisms showed no significant difference. Moreover, all allelic combinations also failed to show significant differences in age of onset among the groups. The present study reports that there is no indication that the three polymorphisms in the Fyn gene are associated with the age of schizophrenic onset.

Histone-profiling in prefrontal cortex of schizophrenics and controls

Reductions in neuronal size and glial cell density have been described in the frontal cortex in major psychiatric disorders. In this investigation, we performed a cytoarchitectural assessment within the planum temporale (PT), an auditory association region located within the superior temporal gyrus, using two-dimensional (2D) measures of cell size and density and spatial point pattern analysis. In sections of the PT from subjects with schizophrenia, bipolar disorder, major depressive disorder and controls (15 subjects per group), the laminar distribution and size of all neurons and glial cell nuclei was recorded. Spatial point pattern investigation demonstrated reduced neuronal clustering in bipolar disorder (p=0.033) and schizophrenia (p=0.027) compared with controls. Statistical analyses comparing each of the patient groups with the control group failed to identify differences in neuronal density between groups. Neuronal size was reduced in cortical layer 3 (p=0.02) and glial cell density reduced in cortical layer 6 (p=0.05) in bipolar disorder relative to controls but these findings did not remain significant after adjusting for six layer-wise comparisons. We propose that alterations in cortical cytoarchitecture within this region are subtle and involve reduced clustering of neurons, which may be due to altered neuronal organisation within cortical mini-columns or within cortical layers.

MRNA expression patterns and distribution of white matter neurons in dorsolateral prefrontal cortex of depressed patients differ from those in schizophrenia patients

Background Schizophrenia, bipolar illness, and major depressive disorder have distinct presentations, but share some common symptoms. Hence, some common cellular and molecular abnormalities may be identifiable in these disorders. Methods We examined cell-specific markers in the dorsolateral prefrontal cortex of brains from 18 patients with bipolar or major depressive disorder, and 18 matched controls, using in situ hybridization histochemistry and staining for nicotinamide-dinucleotide phophate-diaphorase (NADPH). The distribution of NADPH-positive interstitial cells of the white matter and the expression of the mRNA for the 67 KD form of glutamic acid decarboxylase (GAD 67) had previously been shown to be altered in prefrontal cortex of schizophrenics. Other markers identifying glutamatergic neuronal populations were α-type II calcium/calmodulin dependent protein kinase (CAMKII-α), brain derived neurotrophic factor, (BDNF) and the putative transcription factor, T-brain–1 (TBR1). Results Expression of GAD 67 and the distribution of NADPH-positive cells in the white matter were not significantly altered in the dorsolateral prefrontal cortex of depressed subjects. Expression of CAMKII-α and TBR1 mRNAs was significantly increased in bipolar patients but not in major depressed patients, and there was a trend toward reduced BDNF expression in both groups. Abnormal patterns of gene expression and neuronal distribution in schizophrenics are markedly different from those in depressed patients. Conclusions The findings that TBR1 and CAMKII-α expression is increased only in bipolar patients suggests abnormalities of specific genes related to a major cortical cell type and its connectivity.

Alterations in MAP2 immunocytochemistry in areas 9 and 32 of schizophrenic prefrontal cortex

A variety of lines of converging evidence implicate the prefrontal cortex (PFC) in schizophrenia. Studies employing Nissl stains have suggested that PFC dendrites may be atrophic in schizophrenia; however, Nissl stains do not reveal dendrites. We employed MAP2 immunocytochemistry, which stains dendrites to examine cortical layers III and V in two areas of the PFC (areas 9 and 32). Occipital cortex (area 17) was examined as a control region. Tissues from seven schizophrenics and seven non-psychiatric controls were examined. Immunostaining was quantitated by area fraction analysis. MAP2 area fraction was decreased in both layers in both regions of PFC, but not in occipital cortex. Area 9 exhibited a 42% reduction in layer V and a 36% reduction in layer III. Area 32 exhibited a 31% reduction in layer V and a 36% reduction in layer III. Neither region exhibited a significant change in the density of pyramidal cells. These data are consistent with the hypothesis of a schizophrenia-associated decrease in dendritic material in the PFC.

Region‐specific and Age‐related Decrease of Parvalbumin Gene Expression in the Prefrontal Cortex of Elderly Patients with Schizophrenia

Background: Multiple studies on schizophrenia have suggested a dysfunction of γ‐aminobutyric acid (GABA) transmission in the prefrontal cortex (PFC) and some vulnerability of the central nervous system to the aging process. Since one of the calcium‐binding proteins, parvalbumin (PV) is a useful marker for a subpopulation of GABAergic local circuit neurons, we determined the PV gene expression in the PFC in schizophrenic brains to study a possible involvement of GABAergic system and its vulnerability, if any, to the aging process.Methods: We attempted a detailed in situ hybridization to determine the PV gene expression throughout the three PFC subregions (Brodmann areas; BAs 9, 10, and 11) from six elderly patients with schizophrenia and five age‐matched normal individuals.Results: The regional levels of PV messenger RNA (mRNA) were significantly decreased in BAs 9 and 10 of schizophrenics compared with controls. The cellular levels were significantly decreased in layers III, IV, and V in BAs 9 and 10 of schizophrenics. However, in BA 11 of schizophrenics, the cellular level was significantly decreased in layer in alone. There were significant reverse correlations between the PV mRNA levels in those areas and the age at death in the schizophrenic group, but not in the controls.Conclusion: The present results not only provide further evidence of a disturbance in GABA transmission in the PFC of schizophrenics, but also suggest that such dysfunction may be region‐specific and vulnerable to the aging process.

Effect of Aging on Gene Expression of Metabotropic Glutamate Receptor 5 and Glutamate Transporter‐1 in the Prefrontal Cortex of Schizophrenics

Background: The involvement of the glutamatergic system in the patho‐physiology of schizophrenia is attracting interest because an antagonist of N‐methyl‐D‐aspartate (NMDA) glutamate receptor has been demonstrated to induce schizophrenic‐like symptoms in normal subjects. The results of previous studies have also suggested that glutamatergic function is reduced in the prefrontal cortex (PFC) of diagnosed schizophrenics. In order to provide additional evidence for this, we investigated whether expression of metabotropic glutamate receptor 5 (mGluR5) and glutamate transporter‐1 (GLT‐1) in the PFC is altered in schizophrenia. Methods: We compared the expression of mGluRS and GLT‐1 by in situ hybridization in Brodmann area 9 (B9) and 10 (B10) of the prefrontal cortex in 5 normal individuals and 5 schizophrenics that were younger than in previous studies, and examined the relationship between age and mRNA expression. Results: There were no significant differences in either mGluR5 or GLT‐1 mRNA expression between the schizophrenics and controls, however, there was a significant correlation to increase mGluR5 mRNA levels in the schizophrenics in both layer III and layer V of B9 with age, a finding not observed in the controls. Conclusion: The results suggest that the brains of schizophrenics may be vulnerable to aging and that the glutamatergic dysfunctions previously reported in schizophrenics may be partly explained by the aging process.