Neuroplasticity and schizophrenia

Levomilnacipran Improves Lipopolysaccharide-Induced Dysregulation of Synaptic Plasticity and Depression-Like Behaviors via Activating BDNF/TrkB Mediated PI3K/Akt/mTOR Signaling Pathway

Depression is a common psychological disease with high morbidity and mortality. Recently, the involvement of synaptic plasticity in the pathogenesis of depression has shed light on the direction of developing novel antidepressants. Levomilnacipran is a newly approved medication for the treatment of adult major depressive disorder. However, the detailed mechanisms underlying its antidepressant-like effects have yet to be illuminated. In this study, we aimed to investigate the role of levomilnacipran in regulating synaptic plasticity and explore the possible molecular mechanisms of its antidepressant effects using a rat model of depression induced by lipopolysaccharide (LPS). The results demonstrated that levomilnacipran (30 mg/kg, i.p.) significantly ameliorated depression-like behaviors in rats, alleviated the dysregulation of synaptic plasticity, and suppressed neuroinflammation within hippocampus induced by LPS-treatment. Levomilnacipran increased the expression of postsynaptic dense 95 (PSD-95) and synaptophysin (Syn) and reversed the imbalance between pro- and anti-inflammatory cytokines within hippocampus of depressed rats. Additionally, levomilnacipran elevated expression level of brain-derived neurotrophic factor (BDNF), accompanied by increased tyrosine kinase B (TrkB), phosphorylated phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (p-Akt), and phosphorylated mammalian target of rapamycin (p-mTOR). Taken together, these results suggest that levomilnacipran may exert antidepressant effects via upregulating BDNF/TrkB mediated PI3K/Akt/mTOR signaling pathway to improve synaptic plasticity. These findings reveal potential mechanisms for the antidepressant effects of levomilnacipran and offer new insights into the treatments for depression.

Treating cognitive impairment in schizophrenia with GLP-1RAs: an overview of their therapeutic potential

INTRODUCTION

Schizophrenia is a neuropsychiatric disorder that affects approximately 1% of individuals worldwide. There are no available medications to treat cognitive impairment in this patient population currently. Preclinical evidence suggests that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) improve cognitive function. There is a need to evaluate how GLP-1 RAs alter specific domains of cognition and whether they will be of therapeutic benefit in individuals with schizophrenia.

AREAS COVERED

This paper summarizes the effects of GLP-1 RAs on metabolic processes in the brain and how these mechanisms relate to improved cognitive function. We provide an overview of preclinical studies that demonstrate GLP-1 RAs improve cognition and comment on their potential therapeutic benefit in individuals with schizophrenia.

EXPERT OPINION

To understand the benefits of GLP-1 RAs in individuals with schizophrenia, further preclinical research with rodent models relevant to schizophrenia symptomology are needed. Moreover, preclinical studies must focus on using a wider range of behavioral assays to understand whether important aspects of cognition such as executive function, attention, and goal-directed behavior are improved using GLP-1 RAs. Further research into the specific mechanisms of how GLP-1 RAs affect cognitive function and their interactions with antipsychotic medication commonly prescribed is necessary.

Multi-targeted drug design strategies for the treatment of schizophrenia

INTRODUCTION

Schizophrenia is a complex psychiatric disease (or a conglomeration of disorders) manifesting with positive, negative and cognitive symptoms. The pathophysiology of schizophrenia is not completely known; however, it involves many neurotransmitters and their receptors. In order to treat schizophrenia, drugs need to be multi-target drugs. Indeed, the action of second and third generation antipsychotics involves interactions with many receptors, belonging mainly to aminergic GPCRs.

AREAS COVERED

In this review, the authors summarize current concepts of schizophrenia with the emphasis on the modern dopaminergic, serotoninergic, and glutamatergic hypotheses. Next, they discuss treatments of the disease, stressing multi-target antipsychotics. They cover different aspects of design of multi-target ligands, including the application of molecular modeling approaches for the design and benefits and limitations of multifunctional compounds. Finally, they present successful case studies of multi-target drug design against schizophrenia.

EXPERT OPINION

Treatment of schizophrenia requires the application of multi-target drugs. While designing single target drugs is relatively easy, designing multifunctional compounds is a challenge due to the necessity to balance the affinity to many targets, while avoiding promiscuity and the problems with drug-likeness. Multi-target drugs bring many benefits: better efficiency, fewer adverse effects, and drug-drug interactions and better patient compliance to drug regime.

Varenicline for cognitive impairment in people with schizophrenia: systematic review and meta-analysis

BACKGROUND

People with schizophrenia frequently have cognitive dysfunction, which does not respond to pharmacological interventions. Varenicline has been identified as a potential treatment option for nicotinic receptor dysfunction with a potential to treat cognitive impairment in schizophrenia.

METHODS

We conducted a systematic review of Pubmed, Embase, Psycinfo, CINAHL and the Cochrane Schizophrenia Trial Registry for randomised controlled trials of varenicline in people with schizophrenia for cognitive dysfunction. We excluded trials among people with dementia. We then undertook a meta-analysis with the primary outcome of difference in change of cognitive measures between varenicline and placebo as well as secondary outcomes of difference in rates of adverse events. We conducted a sensitivity analysis on smoking status and study duration.

RESULTS

We included four papers in the meta-analysis (n = 339). Varenicline was not superior to placebo for overall cognition (SMD = -0.022, 95% CI -0.154-0.110; Z = -0.333; p = 0.739), attention (SMD = -0.047, 95% CI -0.199-0.104; Z = -0.613; p = 0.540), executive function (SMD = -0.060, 95% CI -0.469-0.348; Z =- 0.290; p = 0.772) or processing speed (SMD = 0.038, 95% CI -0.232-0.308; Z = 0.279; p = 0.780). There was no difference in psychotic symptoms, but varenicline was associated with higher rates of nausea. Sensitivity analyses for smoking status and study duration did not alter the results.

CONCLUSION

Within the present literature, varenicline does not appear to be a useful target compound for improving cognitive impairment in schizophrenia. Based on these results, a trial would need over 2500 participants to be powered to show statistically significant findings.

Developmental aspects of schizophrenia and related disorders: possible implications for treatment strategies

Schizophrenia and other schizophrenia-spectrum disorders are neurodevelopmental disorders which may share genetic susceptibility factors and represent differential expressions of an underlying vulnerability. Schizophrenia may have its onset in childhood and can be reliably diagnosed. However, developmental factors modulate disease expression in children. Although the prevalence of schizophrenia in childhood is low, children who develop schizophrenia in adult life may show subtle and non-specific developmental abnormalities, consistent with the neurodevelopmental hypothesis. Studies of the schizophrenia prodrome also demonstrate that abnormalities may be apparent years before the onset of positive symptoms. Such evidence raises the possibility of using preventive approaches in the treatment of schizophrenia. Further advances in our knowledge of the aetiopathology of schizophrenia (and the identification of endophenotypes within the group of schizophrenia and related disorders) may further improve our ability to predict disease development, making implementation of preventive interventions more achievable.

Altered Motor-Striatal Plasticity and Cortical Functioning in Patients with Schizophrenia

Patients with schizophrenia undergo changes in brain plasticity. In the present study, we characterized motor cortical-striatal plasticity in such patients. Compared with the potentiation following high-frequency repetitive transcranial magnetic stimulation in the control group, the patients demonstrated impaired plasticity of corticostriatal motor-evoked potentials recorded from hand muscles. Notably, the loss of cortical plasticity was correlated with impaired motor learning in a rotary pursuit task. Moreover, the loss of plasticity was correlated with the symptoms of schizophrenia. The results suggest that the progression of schizophrenia is accompanied by altered cortical plasticity and functioning.

A Case Study on Promoting Neuroplasticity in a Patient With Schizophrenia

PURPOSE

The purpose of this study is to introduce the concept of neuroplasticity, explore strategies that psychiatric nurse practitioners can use to improve cognitive functioning, and apply these strategies to a case study of a patient diagnosed with schizophrenia.

DESIGN AND METHODS

This study used an explanatory descriptive approach with a single-case study to describe cognitive functioning in people with schizophrenia and to illustrate practical implications.

FINDINGS

Schizophrenia is a severe mental illness with typical onset in late adolescence and young adulthood. Cognitive impairment often accompanies schizophrenia and may lead to significant functional impairment. Research demonstrates that the brain is able to change (neuroplasticity) in response to environmental stimuli either negatively or positively. Evidence suggests intervention, including cognitive remediation, physical activity, and sleep, can positively modify neuroplasticity in schizophrenia and improve cognitive function, which may lead to improved quality of life.

PRACTICE IMPLICATIONS

Psychiatric mental health nurses need to offer cognitive enhancing strategies to take advantage of neuroplasticity. Ongoing nursing education regarding therapeutic neurocognitive approaches from basic research should be emphasized.

Preliminary analysis of positive and negative syndrome scale in ketamine-associated psychosis in comparison with schizophrenia

OBJECTIVE

Studies of the effects of the N-methyl-d-aspartate (NMDA) glutamate receptor antagonist, ketamine, have suggested similarities to the symptoms of schizophrenia. Our primary goal was to evaluate the dimensions of the Positive and Negative Syndrome Scale (PANSS) in ketamine users (acute and chronic) compared to schizophrenia patients (early and chronic stages).

METHOD

We conducted exploratory factor analysis for the PANSS from four groups: 135 healthy subject administrated ketamine or saline, 187 inpatients of ketamine abuse; 154 inpatients of early course schizophrenia and 522 inpatients of chronic schizophrenia. Principal component factor analyses were conducted to identify the factor structure of the PANSS.

RESULTS

Factor analysis yielded five factors for each group: positive, negative, cognitive, depressed, excitement or dissociation symptoms. The symptom dimensions in two schizophrenia groups were consistent with the established five-factor model (Wallwork et al., 2012). The factor structures across four groups were similar, with 19 of 30 symptoms loading on the same factor in at least 3 of 4 groups. The factors in the chronic ketamine group were more similar to the factors in the two schizophrenia groups rather than to the factors in the acute ketamine group. Symptom severities were significantly different across the groups (Kruskal-Wallis χ(2)(4) = 540.6, p < 0.0001). Symptoms in the two ketamine groups were milder than in the two schizophrenia groups (Cohen's d = 0.7).

CONCLUSION

Our results provide the evidence of similarity in symptom dimensions between ketamine psychosis and schizophrenia psychosis. The interpretations should be cautious because of potential confounding factors.

What causes aberrant salience in schizophrenia? A role for impaired short-term habituation and the GRIA1 (GluA1) AMPA receptor subunit

The GRIA1 locus, encoding the GluA1 (also known as GluRA or GluR1) AMPA glutamate receptor subunit, shows genome-wide association to schizophrenia. As well as extending the evidence that glutamatergic abnormalities have a key role in the disorder, this finding draws attention to the behavioural phenotype of Gria1 knockout mice. These mice show deficits in short-term habituation. Importantly, under some conditions the attention being paid to a recently presented neutral stimulus can actually increase rather than decrease (sensitization). We propose that this mouse phenotype represents a cause of aberrant salience and, in turn, that aberrant salience (and the resulting positive symptoms) in schizophrenia may arise, at least in part, from a glutamatergic genetic predisposition and a deficit in short-term habituation. This proposal links an established risk gene with a psychological process central to psychosis and is supported by findings of comparable deficits in short-term habituation in mice lacking the NMDAR receptor subunit Grin2a (which also shows association to schizophrenia). As aberrant salience is primarily a dopaminergic phenomenon, the model supports the view that the dopaminergic abnormalities can be downstream of a glutamatergic aetiology. Finally, we suggest that, as illustrated here, the real value of genetically modified mice is not as 'models of schizophrenia' but as experimental tools that can link genomic discoveries with psychological processes and help elucidate the underlying neural mechanisms.

The utility of rat models of impulsivity in developing pharmacotherapies for impulse control disorders

High levels of impulsive behaviours are a clinically significant symptom in a range of psychiatric disorders, such as attention deficit hyperactivity disorder, bipolar disorder, personality disorders, pathological gambling and substance abuse. Although often measured using questionnaire assessments, levels of different types of impulsivity can also be determined using behavioural tests. Rodent analogues of these paradigms have been developed, and similar neural circuitry has been implicated in their performance in both humans and rats. In the current review, the methodology underlying the measurement of different aspects of impulsive action and choice are considered from the viewpoint of drug development, with a focus on the continuous performance task (CPT), stop-signal task (SST), go/no-go and delay-discounting paradigms. Current issues impeding translation between animal and human studies are identified, and comparisons drawn between the acute effects of dopaminergic, noradrenergic and serotonergic compounds across species. Although the field could benefit from a more systematic determination of different pharmacological agents across paradigms, there are signs of strong concordance between the animal and human data. However, the type of impulsivity measured appears to play a significant role, with the SST and delay discounting providing more consistent effects for dopaminergic drugs, while the CPT and SST show better predictive validity so far for serotonergic and noradrenergic compounds. Based on the available data, it would appear that these impulsivity models could be used more widely to identify potential pharmacotherapies for impulse control disorders. Novel targets within the glutamatergic and serotonergic system are also suggested.

Effects of antipsychotics on the serum BDNF levels in schizophrenia

Brain-derived neurotrophic factor (BDNF) is active during a critical developmental period and likely influences the neuroplasticity of schizophrenia. This study longitudinally examined the effects of atypical antipsychotics on serum BDNF levels in schizophrenic patients. Specifically, this study measured serum BDNF levels in 53 patients with paranoid schizophrenia during a relapse and again 4 weeks following the administration of antipsychotic treatment (with risperidone in 32 cases, and clozapine in 21 cases). BDNF levels remained unchanged relative to study entry after 4 weeks of atypical antipsychotic treatment. However, serum BDNF was significantly increased in the subgroup receiving risperidone compared to that receiving clozapine, albeit only in the 15 male subjects and not in the 17 females. These results suggest that gender might significantly influence the antipsychotic treatment of schizophrenia from the perspective of BDNF. These findings may also indicate that the treatment with atypical antipsychotic agents differentially affects BDNF levels.

OPCML gene as a schizophrenia susceptibility locus in Thai population

Opioid-binding protein/cell adhesion molecule (OPCML) gene has been recently identified as a susceptibility gene for schizophrenia in Europeans. This study aims to investigate the association between single nucleotide polymorphisms (SNPs) in the OPCML gene and risk of schizophrenia in a Thai population. DNA samples of 115 schizophrenia patients and 173 normal controls were genotyped using high-resolution melting analysis and analyzed by chi-square test of SPSS software. We observed a strong association between an intronic SNP of the OPCML gene (rs1784519) and the risk of schizophrenia in the Thai population [P = 0.00036; odds ratio for the minor A allele, 2.11(1.57-2.84)]. The previously discovered SNP associated with schizophrenia in Europeans, rs3016384, also showed significant association with schizophrenia in the Thai population [P = 0.01; odds ratio of the minor T allele, 0.59 (0.44-0.79)]. Therefore, the OPCML gene is considered to be a schizophrenia-susceptible gene in the Thai population.

Neuroanatomical correlates of different vulnerability states for psychosis and their clinical outcomes

BACKGROUND

Structural brain abnormalities have been described in individuals with an at-risk mental state for psychosis. However, the neuroanatomical underpinnings of the early and late at-risk mental state relative to clinical outcome remain unclear.

AIMS

To investigate grey matter volume abnormalities in participants in a putatively early or late at-risk mental state relative to their prospective clinical outcome.

METHOD

Voxel-based morphometry of magnetic resonance imaging data from 20 people with a putatively early at-risk mental state (ARMS-E group) and 26 people with a late at-risk mental state (ARMS-L group) as well as from 15 participants with at-risk mental states with subsequent disease transition (ARMS-T group) and 18 participants without subsequent disease transition (ARMS-NT group) were compared with 75 healthy volunteers.

RESULTS

Compared with healthy controls, ARMS-L participants had grey matter volume losses in frontotemporolimbic structures. Participants in the ARMS-E group showed bilateral temporolimbic alterations and subtle prefrontal abnormalities. Participants in the ARMS-T group had prefrontal alterations relative to those in the ARMS-NT group and in the healthy controls that overlapped with the findings in the ARMS-L group.

CONCLUSIONS

Brain alterations associated with the early at-risk mental state may relate to an elevated susceptibility to psychosis, whereas alterations underlying the late at-risk mental state may indicate a subsequent transition to psychosis.

Functional magnetic resonance imaging (fMRI) of attention processes in presumed obligate carriers of schizophrenia: preliminary findings

BACKGROUND

Presumed obligate carriers (POCs) are the first-degree relatives of people with schizophrenia who, although do not exhibit the disorder, are in direct lineage of it. Thus, this subpopulation of first-degree relatives could provide very important information with regard to the investigation of endophenotypes for schizophrenia that could clarify the often contradictory findings in schizophrenia high-risk populations. To date, despite the extant literature on schizophrenia endophenotypes, we are only aware of one other study that examined the neural mechanisms that underlie cognitive abnormalities in this group. The aim of this study was to investigate whether a more homogeneous group of relatives, such as POCs, have neural abnormalities that may be related to schizophrenia.

METHODS

We used functional magnetic resonance imaging (fMRI) to collect blood oxygenated level dependent (BOLD) response data in six POCs and eight unrelated healthy controls while performing under conditions of sustained, selective and divided attention.

RESULTS

The POCs indicated alterations in a widely distributed network of regions involved in attention processes, such as the prefrontal and temporal (including the parahippocampal gyrus) cortices, in addition to the anterior cingulate gyrus. More specifically, a general reduction in BOLD response was found in these areas compared to the healthy participants during attention processes.

CONCLUSION

These preliminary findings of decreased activity in POCs indicate that this more homogeneous population of unaffected relatives share similar neural abnormalities with people with schizophrenia, suggesting that reduced BOLD activity in the attention network may be an intermediate marker for schizophrenia.

Olanzapine, but not haloperidol, enhances PSA-NCAM immunoreactivity in rat prefrontal cortex

Repeated antipsychotic treatment may produce adaptive changes ranging from cytoarchitectural rearrangements to synaptic modifications that might contribute to clinical improvement. We performed a prolonged treatment (2 wk) with the first-generation antipsychotic (FGA) haloperidol (1 mg/kg) and the second-generation antipsychotic (SGA) olanzapine (2 mg/kg twice daily) and analysed the expression of the polysialylated form of neural cell adhesion molecule (PSA-NCAM) in rat hippocampus and prefrontal cortex via immunohistochemistry. We found a regional- and drug-selective increase of PSA-NCAM expression in prefrontal cortex of olanzapine-treated rats with no effects in hippocampus; conversely, haloperidol did not produce a change in either brain region. Our findings reveal a possible role for PSA-NCAM in the mechanism of action of the SGA olanzapine adding complexity as well as specificity to the molecular changes set in motion by this drug.

Dopamine acting through D2 receptors modulates the expression of PSA-NCAM, a molecule related to neuronal structural plasticity, in the medial prefrontal cortex of adult rats

A "neuroplastic" hypothesis proposes that changes in neuronal structural plasticity may underlie the aetiology of depression and the action of antidepressants. The medial prefrontal cortex (mPFC) is affected by this disorder and shows an intense expression of the polysialylated form of the neural cell adhesion molecule (PSA-NCAM), a plasticity-associated molecule, which is expressed mainly in interneurons. The monoamines serotonin, dopamine and noradrenaline are the principal targets of antidepressant action. Pharmacological manipulation of serotonin levels regulates synaptophysin and PSA-NCAM expression in the adult mPFC. However, the involvement of structural plasticity on the antidepressant effects of dopamine has not been well explored yet. Using immunohistochemistry, we have studied the relationship between dopaminergic fibers and PSA-NCAM expressing neurons in the mPFC and the expression of D2 receptors. In order to evaluate the effects of dopamine in neuronal structural plasticity and on inhibitory neurotransmission, we have analyzed the expression of synaptophysin, PSA-NCAM and GAD67 in the mPFC after cortical dopamine depletion with 6-OHDA and after chronic treatments with the D2 receptor antagonist haloperidol or the D2 receptor agonist PPHT. Many dopaminergic fibers were observed in close apposition to PSA-NCAM expressing neurons and 76% of these cells co-expressed D2 receptor. Both haloperidol treatment and 6-OHDA injection reduced significantly PSA-NCAM, synaptophysin and GAD67 expression in the mPFC. Conversely, PPHT treatment increased the expression of these molecules. Our results give support to the "neuroplastic" hypothesis of depression, suggesting that dopamine acting on D2 receptors may modulate neuronal structural plasticity and inhibitory neurotransmission through changes in PSA-NCAM expression.

Haloperidol and clozapine differentially affect the expression of arrestins, receptor kinases, and extracellular signal-regulated kinase activation

Dopamine and other G protein-coupled receptors (GPCRs) represent the major target of antipsychotic drugs. GPCRs undergo desensitization via activation-dependent phosphorylation by G protein-coupled receptor kinases (GRKs) followed by arrestin binding. Arrestins and GRKs are major regulators of GPCR signaling. We elucidated changes in expression of two arrestins and four GRKs following chronic (21 days) treatment with haloperidol (1 mg/kg i.p.) or clozapine (20 mg/kg i.p.) 2 or 24 h after the last injection in 11 brain regions. Haloperidol decreased GRK3 in ventrolateral caudate-putamen and transiently down-regulated GRK5 in globus pallidus and caudal caudate-putamen. Clozapine also caused a short-term suppression of the GRK5 expression in the caudal caudate-putamen and globus pallidus, but, unlike haloperidol, elevated GRK5 in the caudal caudate-putamen after 24 h. Unlike haloperidol, clozapine decreased arrestin2 and GRK3 in hippocampus and GRK3 in globus pallidus but increased arrestin2 in the core of nucleus accumbens and ventrolateral caudate-putamen and GRK2 in prefrontal cortex. Clozapine, but not haloperidol, induced long-term activation of extracellular signal-regulated kinase (ERK) 2 in ventrolateral caudate-putamen and transient in prefrontal cortex. The data demonstrate that haloperidol and clozapine differentially affect the expression of arrestins and GRKs and ERK activity, which may play a role in determining their clinical profile.

Brain neuroplasticity in healthy, hyperactive and psychotic children: insights from neuroimaging

Noninvasive brain imaging permits longitudinal studies of anatomic brain development in healthy and psychiatrically ill children. The time course for gray matter maturation varies by region and parallels earlier histological studies, indicating dynamic patterns of overproduction and regression. Developmental trajectories vary in relation to gender, intelligence, and overall functioning. Twin studies show high heritability for brain volumes, which varies with region and with age. Diagnostically specific, illness-related changes as well as outcome-associated plastic response are observed as illustrated for two pediatric populations, childhood-onset schizophrenia and attention-deficit/hyperactivity disorder, conditions which may be, in part, disorders of brain plasticity.

PSA-NCAM expression in the human prefrontal cortex

The prefrontal cortex (PFC) of adult rodents is capable of undergoing neuronal remodeling and neuroimaging studies in humans have revealed that the structure of this region also appears affected in different psychiatric disorders. However, the cellular mechanisms underlying this plasticity are still unclear. The polysialylated form of the neural cell adhesion molecule (PSA-NCAM) may mediate these structural changes through its anti-adhesive properties. PSA-NCAM participates in neurite outgrowth and synaptogenesis and changes in its expression occur parallel to neuronal remodeling in certain regions of the adult brain. PSA-NCAM is expressed in the hippocampus and temporal cortex of adult humans, but it has not been studied in the PFC. Employing immunohistochemistry on sections from the rostromedial superior frontal gyrus we have found that PSA-NCAM is expressed in the human PFC neuropil following a laminated pattern and in a subpopulation of mature neurons, which lack doublecortin expression. Most of these cells have been identified as interneurons expressing calbindin. The expression of PSA-NCAM in the human PFC is similar to that of rodents. Since this molecule has been linked to the neuronal remodeling found in experimental models of depression, it may also participate in the structural plasticity described in the PFC of depressed patients.

Intrinsic sensory deprivation induced by neonatal capsaicin treatment induces changes in rat brain and behaviour of possible relevance to schizophrenia

Schizophrenia is considered to be a neurodevelopmental disorder with origins in the prenatal or neonatal period. Brains from subjects with schizophrenia have enlarged ventricles, reduced cortical thickness (CT) and increased neuronal density in the prefrontal cortex compared with those from normal subjects. Subjects with schizophrenia have reduced pain sensitivity and niacin skin flare responses, suggesting that capsaicin-sensitive primary afferent neurons might be abnormal in schizophrenia. This study tested the hypothesis that intrinsic somatosensory deprivation, induced by neonatal capsaicin treatment, causes changes in the brains of rats similar to those found in schizophrenia. Wistar rats were treated with capsaicin, 50 mg kg(-1) subcutaneously, or vehicle (control) at 24-36 h of life. At 5-7 weeks behavioural observations were made, and brains removed, fixed and sectioned. The mean body weight of capsaicin-treated rats was not significantly different from control, but the mean brain weight of male, but not female, rats, was significantly lower than control. Capsaicin-treated rats were hyperactive compared with controls. The hyperactivity was abolished by haloperidol. Coronal brain sections of capsaicin-treated rats had smaller cross-sectional areas, reduced CT, larger ventricles and aqueduct, smaller hippocampal area and reduced corpus callosum thickness, than brain sections from control rats. Neuronal density was increased in several cortical areas and the caudate putamen, but not in the visual cortex. It is concluded that neonatal capsaicin treatment of rats produces brain changes that are similar to those found in brains of subjects with schizophrenia.

Hippocampal and parahippocampal volumes in schizophrenia: a structural MRI study

Smaller medial temporal lobe volume is a frequent finding in studies of patients with schizophrenia, but the relative contributions of the hippocampus and three surrounding cortical regions (entorhinal cortex, perirhinal cortex, and parahippocampal cortex) are poorly understood. We tested the hypothesis that the volumes of medial temporal lobe regions are selectively changed in schizophrenia. We studied 19 male patients with schizophrenia and 19 age-matched male control subjects. Hippocampal and cortical volumes were estimated using a three-dimensional morphometric protocol for the analysis of high-resolution structural magnetic resonance images, and repeated measures ANOVA was used to test for region-specific differences. Patients had smaller overall medial temporal lobe volumes compared to controls. The volume difference was not specific for either region or hemisphere. The finding of smaller medial temporal lobe volumes in the absence of regional specificity has important implications for studying the functional role of the hippocampus and surrounding cortical regions in schizophrenia.

PSA-NCAM expression in the rat medial prefrontal cortex

The rat medial prefrontal cortex, an area considered homologous to the human prefrontal cortex, is a region in which neuronal structural plasticity has been described during adulthood. Some plastic processes such as neurite outgrowth and synaptogenesis are known to be regulated by the polysialylated form of the neural cell adhesion molecule (PSA-NCAM). Since PSA-NCAM is present in regions of the adult CNS which are undergoing structural remodeling, such as the hypothalamus or the hippocampus, we have analyzed the expression of this molecule in the medial prefrontal cortex of adult rats using immunohistochemistry. PSA-NCAM immunoreactivity was found both in cell bodies and in the neuropil of the three divisions of the medial prefrontal cortex. All cell somata expressing PSA-NCAM corresponded to neurons and 5' bromodeoxyuridine labeling after long survival times demonstrated that these neurons were not recently generated. Many of these PSA-NCAM immunoreactive neurons in the medial prefrontal cortex could be classified as interneurons on the basis of their morphology and glutamate decarboxylase, isoform 67 expression. Some of the PSA-NCAM immunoreactive neurons also expressed somatostatin, neuropeptide Y and calbindin-D28K. By contrast, pyramidal neurons in this cortical region did not appear to express PSA-NCAM. However, some of these principal neurons appeared surrounded by PSA-NCAM immunoreactive puncta. Some of these puncta co-expressed synaptophysin, suggesting the presence of synapses. Since the etiology of some psychiatric disorders has been related to alterations in medial prefrontal cortex structural plasticity, the study of PSA-NCAM expression in this region may open a new approach to the pathophysiology of these mental disorders.