Human postmortem tissue: what quality markers matter?

Postmortem human brain tissue is used for the study of many different brain diseases. A key factor in conducting postmortem research is the quality of the tissue. Unlike animal tissue, whose condition at death can be controlled and influenced, human tissue can only be collected naturalistically. This introduces potential confounds, based both on pre- and postmortem conditions, that may influence the quality of tissue and its ability to yield accurate results. The traditionally recognized confounds that reduce tissue quality are agonal factors (e.g., coma, hypoxia, hyperpyrexia at the time of death), and long postmortem interval (PMI). We measured tissue quality parameters in over 100 postmortem cases collected from different sources and correlated them with RNA quality (as indicated by the RNA Integrity Number (RIN)) and with protein quality (as measured by the level of representative proteins). Our results show that the most sensible indicator of tissue quality is RIN and that there is a good correlation between RIN and the pH. No correlation developed between protein levels and the aforementioned factors. Moreover, even when RNA was degraded, the protein levels remained stable. However, these correlations did not prove true under all circumstances (e.g., thawed tissue, surgical tissue), that yielded unexpected quality indicators. These data also suggest that cases whose source was a Medical Examiner's office represent high tissue quality.

Multidose risperidone treatment evaluated in a rodent model of tardive dyskinesia

Risperidone is a second-generation antipsychotic that lacks acute motor side effects at low doses (<6 mg/day), but above this level is associated with parkinsonism and akathesia. The literature suggests an association between acute motor side effects and tardive dyskinesia (TD); therefore, we hypothesized that low dose levels of risperidone will spare TD. As clinical studies of TD liability with fixed doses of risperidone are difficult to conduct, we tested low and high doses of risperidone in a rodent model of TD, vacuous chewing movements (VCMs) production. Low doses of risperidone (1.5 mg/kg/day) resulted in control levels of VCMs after 6 months of treatment, whereas high doses of risperidone (6 mg/kg/day) produced VCM in the same range as haloperidol. Plasma drug levels are reported. If this animal model predicts TD risk in humans, the TD liability with low-dose risperidone is at a placebo level, whereas higher doses show haloperidol-like TD risk, as predicted from the acute motor effects.

Insight and frontal cortical function in schizophrenia: a review

Insight into illness has been identified as a clinically important phenomenon, in no small part due to an association with treatment-adherence. An increasing number of studies, but not all, have observed poor insight to be a reflection of cognitive dysfunction in schizophrenia. A review of 34 published English-language studies found a significant number (i.e., 21) reporting a relationship between insight deficits and impaired performance on cognitive tasks primarily mediated by frontal cortex. A significant number of reviewed studies examined insight function in more than one psychiatric population, including bipolar and schizoaffective disorder. The most replicated findings from these studies were the correlations between insight deficits and impaired performance on the Wisconsin Card Sorting Test (WCST). More specifically, WCST perseverative errors correlated positively and the number of categories completed correlated negatively with poor insight, suggesting that impaired insight may be mediated by deficiencies in conceptual organization and flexibility in abstract thinking. Since the WCST requires the ability to demonstrate conceptual flexibility through the generation, maintenance and switching of mental sets along with the capacity to use verbal feedback to correct errors, it would appear that such 'executive' functions are most related to insight. In addition, recently identified structural correlates of poor insight in schizophrenia show some association with anosognosia in neurological patients. This review will discuss the implications of these findings and directions for future research.

The neurobiology of cognition in schizophrenia

Cognitive dysfunction in schizophrenia differs from cognitive dysfunction in neurodegenerative illnesses because it is associated with neuronal dysfunction and not neurodegeneration. Pharmacologically, potential targets for developing treatments may differ from cognition in dementing disorders. Several putative molecular targets for treating cognition in schizophrenia show promise, such as treatments that act on the D(1) receptor of the dopamine system; the 5HT(1A), 5HT(2A), and 5HT(6), receptors of the serotonin system; and ampakines, Glycine/D-cycloserine, D-serine, and mGluR 2/3 agonists of the glutamatergic system. Other receptors associated with improvement in cognition include nicotinic and muscarinic receptors, and the alphalpha2 subunit receptor of the brain GABA system. Domain treatment of schizophrenia is a new method of treating schizophrenia that involves treating a single domain of dysfunction at a time.

Phosphorylation of the tubulin-binding protein, stathmin, by Cdk5 and MAP kinases in the brain

Regulation of cytoskeletal dynamics is essential to neuronal plasticity during development and adulthood. Dysregulation of these mechanisms may contribute to neuropsychiatric and neurodegenerative diseases. The neuronal protein kinase, cyclin-dependent kinase 5 (Cdk5), is involved in multiple aspects of neuronal function, including regulation of cytoskeleton. A neuroproteomic search identified the tubulin-binding protein, stathmin, as a novel Cdk5 substrate. Stathmin was phosphorylated by Cdk5 in vitro at Ser25 and Ser38, previously identified as mitogen-activated protein kinase (MAPK) and p38 MAPKdelta sites. Cdk5 predominantly phosphorylated Ser38, while MAPK and p38 MAPKdelta predominantly phosphorylated Ser25. Stathmin was phosphorylated at both sites in mouse brain, with higher levels in cortex and striatum. Cdk5 knockout mice exhibited decreased phospho-Ser38 levels. During development, phospho-Ser25 and -Ser38 levels peaked at post-natal day 7, followed by reduction in total stathmin. Inhibition of protein phosphatases in striatal slices caused an increase in phospho-Ser25 and a decrease in total stathmin. Interestingly, the prefrontal cortex of schizophrenic patients had increased phospho-Ser25 levels. In contrast, total and phospho-Ser25 stoichiometries were decreased in the hippocampus of Alzheimer's patients. Thus, microtubule regulatory mechanisms involving the phosphorylation of stathmin may contribute to developmental synaptic pruning and structural plasticity, and may be involved in neuropsychiatric and neurodegenerative disorders.

Correlations between rCBF and symptoms in two independent cohorts of drug-free patients with schizophrenia

We report on the correlations between whole brain rCBF and the positive and negative symptoms of schizophrenia in two cohorts of patients who were scanned while free of antipsychotic medication. We hypothesized that positive symptoms would correlate with rCBF in limbic and paralimbic regions, and that negative symptoms would correlate with rCBF in frontal and parietal regions. Both cohorts of patients with schizophrenia (Cohort 1: n=32; Cohort 2: n=23) were scanned using PET with H(2)(15)O while free of antipsychotic medication for an average of 21 and 15 days, respectively. Both groups were scanned during a resting state. Using SPM99, we conducted pixel by pixel linear regression analyses between BPRS scores and whole brain rCBF. As hypothesized, positive symptoms correlated with rCBF in the anterior cingulate cortex (ACC) in a positive direction and with the hippocampus/parahippocampus in a negative direction in both patient groups. When the positive symptoms were further divided into disorganization and hallucination/delusion scores, similar positive correlations with ACC and negative correlations with hippocampus rCBF were found. In both cohorts, the disorganization scores correlated positively with rCBF in Broca's area. As expected, negative symptoms correlated inversely with rCBF in frontal and parietal regions. This study provides evidence that limbic dysfunction may underlie the production of positive symptoms. It suggests that abnormal function of Broca's area may add a specific language-related dimension to positive symptoms. This study also provides further support for an independent neurobiological substrate of negative symptoms distinct from positive symptoms. The involvement of both frontal and parietal regions is implicated in the pathophysiology of negative symptoms.

Regional alterations in RGS4 protein in schizophrenia

The regulator of G protein signaling (RGS) molecules are a class of proteins that modulate the signaling activity of G-protein coupled receptors. Regulator of G protein signaling 4 (RGS4) is of particular interest in schizophrenia since it is associated with the dopamine (DA) receptor, its expression is altered in affected CNS tissue, and polymorphisms in the RGS4 gene are being examined as risk factors for the disease (Morris et al.2004, Am J Med Genet B Neuropsychiatr Genet 125:50-53; Prasad et al.2005, Mol Psychiatry 10:213-219; Williams et al.2004, Biol Psychiatry 55:192-195). To further test for the involvement of RGS4 expression in schizophrenia, we examined a selection of different cortical and subcortical regions in human brain for alterations in RGS4 mRNA and protein expression. To evaluate the effect of antipsychotic medication on RGS4 expression levels, we compared a subset of treated and untreated cases that were off antipsychotic medication for at least 3 months prior to death. We report a significant decrease in RGS4 mRNA levels in the cingulate gyrus, superior frontal gyrus, and the insular cortex of all schizophrenia cases when compared with controls. A decrease in RGS4 mRNA was also observed in the caudate, but only in the medicated schizophrenia cases. Measurement of protein levels using Western blot demonstrated that RGS4 protein is decreased in the frontal cortex of schizophrenia cases.

Effects of noncompetitive NMDA receptor blockade on anterior cingulate cerebral blood flow in volunteers with schizophrenia

Schizophrenia may be related to dysfunctional glutamatergic activity, specifically hypofunction of the N-methyl-D-aspartate receptor (NMDAR). In addition, it has been proposed that NMDAR hypofunction may paradoxically cause an increase in glutamate release and hypermetabolism in corticolimbic regions. If a state of partial, chronic NMDAR blockade underlies schizophrenia, then schizophrenic volunteers (SV) may have greater glutamate release and associated elevations in regional cerebral blood flow (rCBF) than normal volunteers (NV), following drug-induced NMDAR antagonism. Therefore, we have given acute ketamine, a noncompetitive NMDAR antagonist, to NV (n=13) and medicated volunteers with schizophrenia (n=10) in conjunction with serial positron emission tomography blood flow studies. Drug administration caused marked rCBF elevations in frontal and cingulate regions in both groups. Contrasts between NV and SV ketamine groups showed that SV had greater relative blood flow increases in the anterior cingulate than NV. Maximum blood flow, and the area under the curve for blood flow in the anterior cingulate cortex, significantly correlated with changes in psychosis ratings in SV and NV (maximum rCBF only). These changes are consistent with a relatively hypoactive thalamic NMDAR and increased cortical glutamate neurotransmission at non-NMDARs in schizophrenia. We hypothesize that ketamine antagonizes an NMDAR-dependent inhibitory system that is partially compromised in subjects with schizophrenia. The ketamine-induced reduction of inhibition leads to a marked increase in glutamate release and hypermetabolism (elevated rCBF) in frontal and cingulate cortical regions. The loss of inhibition and increased glutamate release may cause the distorted thoughts and diminished cognitive abilities elicited by NMDAR blockade.

Chromatin Alterations Associated With Down-regulated Metabolic Gene Expression in the Prefrontal Cortex of Subjects With Schizophrenia

BACKGROUND

Schizophrenia is frequently accompanied by hypometabolism and altered gene expression in the prefrontal cortex. Cellular metabolism regulates chromatin structure, including covalent histone modifications, which are epigenetic regulators of gene expression.

OBJECTIVE

To test the hypothesis that down-regulated metabolic gene expression is associated with histone modification changes in the prefrontal cortex of subjects with schizophrenia.

DESIGN AND SUBJECTS

Histones and gene transcripts were profiled in the postmortem prefrontal cortex of 41 subjects with schizophrenia and 41 matched controls. The phosphorylation, acetylation, and methylation of 6 lysine, serine, and arginine residues of histones H3 and H4 were examined together with 16 metabolic gene transcripts using serial immunoblotting, immunohistochemical analysis, custom-made complementary DNA arrays, and quantitative real-time reverse transcriptase-polymerase chain reaction.

RESULTS

Subjects with schizophrenia, as a group, showed no significant alterations in histone profiles or gene expression. In a subgroup of 8 patients with schizophrenia, levels of H3-(methyl)arginine 17, H3meR17, exceeded control values by 30%, and this was associated with the decreased expression of 4 metabolic transcripts.

CONCLUSIONS

High levels of H3-(methyl)arginine 17 are associated with down-regulated metabolic gene expression in the prefrontal cortex of a subset of subjects with schizophrenia. Histone modifications may contribute to the pathogenesis of prefrontal dysfunction in schizophrenia.

Subtle effects of ketamine on memory when administered following stimulus presentation

RATIONALE

N-methyl-D-aspartate (NMDA) receptor antagonists (e.g., PCP, ketamine) have been shown to impair learning/memory. Well documented in animal models, only limited research in humans has been reported. Findings to date are similar to results of animal studies; however, antagonists are typically administered before the learning experience. This may be problematic as memory failure could be secondary to inattention induced by the psychotomimetic effects of these drugs and/or alterations in sensory processing which can degrade the quality of the stimulus, thereby affecting the accuracy of recall.

OBJECTIVE

The objective of the study is to compare the effects of ketamine vs placebo on recall for words when administered after stimulus presentation.

METHODS

In this double-blind crossover study, 24 normal controls were given bolus injections of ketamine (0.3 mg/kg) or placebo. Immediately prior to infusion, subjects were administered a verbal memory test. Delayed recall was measured 45 min postinfusion. Mental status changes were assessed using the Brief Psychiatric Rating Scale.

RESULTS

Subjects experienced a significant increase in psychiatric symptoms that peaked at 20 min. Results indicate no differences between the drug and placebo conditions for the memory task. However, reminiscence (i.e., recall of previously unrecalled items with repeated testing) was significantly reduced following ketamine administration compared to placebo.

CONCLUSIONS

Findings suggest that aspects of memory consolidation are affected by drugs that interfere with NMDA receptor function.

Functional effects of single dose first- and second-generation antipsychotic administration in subjects with schizophrenia

Using PET with (15)O water, we characterized the time course of functional brain changes following the acute administration of a first- and a second-generation antipsychotic. Volunteers with schizophrenia were scanned while drug-free (baseline) and after single dose administration of haloperidol (n=6) or olanzapine (n=6) during a time course adapted to their plasma kinetics. To obtain brain location information, we contrasted each post-drug scan to baseline-acquired scans. We plotted the regional cerebral blood flow (rCBF) extracted in these locations and calculated the kinetic characteristics of the curves. Further, we compared and contrasted the rCBF changes induced by the drugs over the first 4 h post-drug administration. Dorsal and ventral striatum, thalamus and anterior cingulate cortex were activated with haloperidol, while frontal, temporal and cerebellum regions evidenced reduced flow. With olanzapine, ventral striatum, anterior cingulate and temporal cortices evidenced increases, and thalamus and lingual cortex decreases, in rCBF. Both drugs activated the caudate nucleus. Haloperidol induced greater activation of the dorsal striatum than did olanzapine. These data reveal important differences in patterns of brain activation between the drugs. Differences in the involvement in basal ganglia parallel known differences between the drugs in the emergence of acute EPS upon emergency administration.

Olanzapine (Zyprexa):charactirestics of a new antipsychotic

Olanzapine is a thienobenzodiszepine antipsychotic,which exerts broad-spectrum receptor antagonism in the central nervous system.It demonstrates regionally selective dopamine antagonist activity as measured with the depolarisation block model and fos activation paradigm. Early in vivo imaging studies suggest a relatively low D2 occupancy in th striatum (69%) with a higher 5-HT2 occupancy in the cortex (84%) of 10 mg.Its pharmaco-kinetics are dose-proportional; Tmax is 5 h and the elimination half-life is 31 h (range:21-54 h). Efficacy studies show equivalent antipsychotic efficacy to haloperidol with the possibility of superior efficacy on negative symptoms and depression. Motor side-effects are minimal with mild akathisia emerging at the highest doses; non-motor side-effects are also minimal. Olanzapine is a highly effective antipsychotic drug with minimal side-effects. It will be an important new drug for treating schizophrenia.

Sertindole (Serdolect): preclinical and clinical findings of a new atypical antipsychotic

This review first describes the preclinical findings with sertindole, a novel phenyl indole derivative antipsychotic agent. Second, a summary is provided of the major clinical trials conducted to date. Based on these findings, sertindole appears to be an effective antipsychotic agent for the treatment of positive and negative symptoms of schizophrenia, with efficacy that is clearly superior to placebo. Sertindole is as effective as haloperidol, however, is much better tolerated with significantly fewer adverse neurologic effects across a wide dosage range of both drugs. Sertindole is associated with a significant mean prolongation of the QT and QTc intervals of 3 - 6% from baseline in placebo-controlled studies. This potential adverse effect should be taken into account when treating specific patients with known risk factors for ventricular arrhythmias. Sertindole should prove to be a very useful addition to the therapeutic options available for the treatment of psychotic disorders.

Phenotype of schizophrenia: a review and formulation

The discovery of the pathophysiology(ies) for schizophrenia is necessary to direct rational treatment directions for this brain disorder. Firm knowledge about this illness is limited to areas of phenomenology, clinical electrophysiology, and genetic risk; some aspects of dopamine pharmacology, cognitive symptoms, and risk genes are known. Basic questions remain about diagnostic heterogeneity, tissue neurochemistry, and in vivo brain function. It is an illness ripe for molecular characterization using a rational approach with a confirmatory strategy; drug discovery based on knowledge is the only way to advance fully effective treatments. This paper reviews the status of general knowledge in this area and proposes an approach to discovery, including identifying brain regions of dysfunction and subsequent localized, hypothesis-driven molecular screening.

Neuroplasticity and schizophrenia

This article's title is also the name of a workshop sponsored by the International Congress on Schizophrenia Research that was focused on an appraisal of the potential role of neuroplastic processes in the etiology or course of schizophrenia. The workshop brought together clinical investigators of schizophrenia and basic scientists who study various aspects of neuroplasticity, including central nervous system (CNS) development, learning and memory, and drug action. The goal was to identify special opportunities to advance knowledge and understanding of schizophrenia pathology, treatment, or prevention by applying neuroplasticity concepts as a framework to theories of the illness. Although the focus of this workshop was schizophrenia, the phenomena considered are pertinent to other disorders, such as depression and drug abuse.

Parametric study of accuracy and response time in schizophrenic persons making visual or auditory discriminations

The inability to modulate processing time in conjunction with varying difficulty levels may be a core component of schizophrenia's cognitive deficit. In this study we used a parametric design to demonstrate this group's inability to increase and decrease response times in association with varying levels of task demand during auditory and visual recognition tasks. Unlike participants with schizophrenia, healthy volunteers responded to increasing levels of difficulty and high error by robustly increasing their average response times. In the group with schizophrenia, the greater the correlation between a subject's Response-Time and error rate the better was the subject in his/her overall discrimination accuracy. The higher their correlations the better they performed across all levels of difficulty in both modalities. The schizophrenia group's tendency to process high and low error conditions with similar behavioral resources may reflect a relatively static, non-dynamic cognitive repertoire.