Traditional and new antipsychotic drugs differentially alter neurotransmission markers in basal ganglia-thalamocortical neural pathways

Treatment of severe tardive dyskinesia with concurrent administration of olanzapine, clonazepam, baclofen, and gabapentin: a case report

BACKGROUND

Long-term use of antipsychotics or other dopamine antagonists can result in the extrapyramidal side effect of tardive dyskinesia (TD).Case presentation: An 18-year-old female patient experienced abnormal speech and behavior and because of an equivocal diagnosis, she was given daily doses of 300 mg of quetiapine and 60 mg of ziprasidone. She had used these medications for 2 years before the appearance of involuntary abnormal movements. These movements, which were classified as TD, steadily worsened and markedly interfered with her daily life. Following a trial-and-error course of therapy with vitamin E, vitamin B6, amantadine, valproic acid sodium, lorazepam, and diazepam, the drugs were gradually reduced and stopped, yet the aberrant movements persisted. Finally, the patient was given olanzapine, clonazepam, baclofen, and gabapentin. The Abnormal Involuntary Movement Scale was used to assess changes in the patient's condition. Her TD was efficiently managed through co-administration of olanzapine, clonazepam, baclofen, and gabapentin.

CONCLUSIONS

The possibility of TD inducing by antipsychotic use is a clinical concern, even though atypical antipsychotics decrease the incidence of extrapyramidal side effects, and it cannot be entirely excluded. This report provides useful insights into the management of TD and will help clinicians manage similar cases.

The substantia nigra in the pathology of schizophrenia: A review on post-mortem and molecular imaging findings

Dysregulation of striatal dopamine is considered to be an important driver of pathophysiological processes in schizophrenia. Despite being one of the main origins of dopaminergic input to the striatum, the (dys)functioning of the substantia nigra (SN) has been relatively understudied in schizophrenia. Hence, this paper aims to review different molecular aspects of nigral functioning in patients with schizophrenia compared to healthy controls by integrating post-mortem and molecular imaging studies. We found evidence for hyperdopaminergic functioning in the SN of patients with schizophrenia (i.e. increased AADC activity in antipsychotic-free/-naïve patients and elevated neuromelanin accumulation). Reduced GABAergic inhibition (i.e. decreased density of GABAergic synapses, lower VGAT mRNA levels and lower mRNA levels for GABA_A receptor subunits), excessive glutamatergic excitation (i.e. increased NR1 and Glur5 mRNA levels and a reduced number of astrocytes), and several other disturbances implicating the SN (i.e. immune functioning and copper concentrations) could potentially underlie this nigral hyperactivity and associated striatal hyperdopaminergic functioning in schizophrenia. These results highlight the importance of the SN in schizophrenia pathology and suggest that some aspects of molecular functioning in the SN could potentially be used as treatment targets or biomarkers.

A systematic review of TMS and neurophysiological biometrics in patients with schizophrenia

BACKGROUND

Transcranial magnetic stimulation can be combined with electromyography (TMS-EMG) and electroencephalography (TMS-EEG) to evaluate the excitatory and inhibitory functions of the cerebral cortex in a standardized manner. It has been postulated that schizophrenia is a disorder of functional neural connectivity underpinned by a relative imbalance of excitation and inhibition. The aim of this review was to provide a comprehensive overview of TMS-EMG and TMS-EEG research in schizophrenia, focused on excitation or inhibition, connectivity, motor cortical plasticity and the effect of antipsychotic medications, symptom severity and illness duration on TMS-EMG and TMS-EEG indices.

METHODS

We searched PsycINFO, Embase and Medline, from database inception to April 2020, for studies that included TMS outcomes in patients with schizophrenia. We used the following combination of search terms: transcranial magnetic stimulation OR tms AND interneurons OR glutamic acid OR gamma aminobutyric acid OR neural inhibition OR pyramidal neurons OR excita* OR inhibit* OR GABA* OR glutam* OR E-I balance OR excitation-inhibition balance AND schizoaffective disorder* OR Schizophrenia OR schizophreni*.

RESULTS

TMS-EMG and TMS-EEG measurements revealed deficits in excitation or inhibition, functional connectivity and motor cortical plasticity in patients with schizophrenia. Increased duration of the cortical silent period (a TMS-EMG marker of γ-aminobutyric acid B receptor activity) with clozapine was a relatively consistent finding.

LIMITATIONS

Most of the studies used patients with chronic schizophrenia and medicated patients, employed cross-sectional group comparisons and had small sample sizes.

CONCLUSION

TMS-EMG and TMS-EEG offer an opportunity to develop a novel and improved understanding of the physiologic processes that underlie schizophrenia and to assess the therapeutic effect of antipsychotic medications. In the future, these techniques may also help predict disease progression and further our understanding of the excitatory/inhibitory balance and its implications for mechanisms that underlie treatment-resistant schizophrenia.

Evaluation of neurotransmitter receptor gene expression identifies GABA receptor changes: a follow-up study in antipsychotic-naïve patients with first-episode psychosis

A study of the gene expression levels in the blood of individuals with schizophrenia in the beginning of the disease, such as first-episode psychosis (FEP), is useful to detect gene expression changes in this disorder in response to treatment. Although a large number of genetic studies on schizophrenia have been conducted, little is known about the effects of antipsychotic treatment on gene expression. The aim of the present study was to examine differences in the gene expression in the blood of antipsychotic-naïve FEP patients before and after risperidone treatment (N = 44) and also to verify the correlation with treatment response. In addition, we determined the correlations between differentially expressed genes and clinical variables. The expression of 40 neurotransmitter and neurodevelopment-associated genes was assessed using the RT2 Profiler PCR Array. The results indicated that the GABRR2 gene was downregulated after risperidone treatment, but no genes were associated with response to treatment and clinical variables after Bonferroni correction. GABRR2 downregulation after treatment can both suggest an effect of risperidone treatment or processes related to disease progression, either not necessarily associated with the improvement of symptoms. Despite this change was observed in blood, this decrease in GABRR2 mRNA levels might be an effect of changes in GABA concentrations or other systems interplay consequently to D2 blockage induced by risperidone, for example. Thus, it is important to consider that antipsychotics or the progression of psychotic disorders might interfere with gene expression.

Olanzapine: a 5-year perspective

Olanzapine is a novel antipsychotic, approved for the acute and maintenance treatment of schizophrenia and bipolar I disorder. Despite the publicity regarding reported adverse events with the novel antipsychotics, such as weight gain and Type II diabetes mellitus, olanzapine remains a useful and important medicine. It is a selective monoaminergic antagonist with high-affinity binding to a number of receptors thought to be implicated in some psychotic and mood symptoms. The complex pharmacology of olanzapine has lead to studies exploring its use in treating substance abuse, aggression/violence, borderline personality disorder, schizotypal personality disorder, obsessive-compulsive disorder and as a neuroprotective agent in schizophrenia. As the pharmacology of olanzapine and other novel antipsychotics becomes better understood, future effective treatment strategies are likely to match an individual's genetic makeup and receptor profiles to the most compatible agent.

Aripiprazole differentially regulates the expression of Gad67 and γ-aminobutyric acid transporters in rat brain

The molecular etiology of schizophrenia comprises abnormal neurotransmission of the amino acid GABA (γ-aminobutyric acid). Neuropathological studies convincingly revealed reduced expression of glutamic acid decarboxylase (Gad67) in GABAergic interneurons. Several antipsychotics influence the expression of GABAergic genes, but aripiprazole (APZ), a partial dopaminergic and serotonergic receptor agonist, has not been involved into these studies so far. We treated Sprague-Dawley rats for 4 weeks or 4 months with APZ suspended in drinking water and doses of 10 and 40 mg per kg body weight. Gene expression of Gad67, the vesicular GABA transporter Slc32a1 (solute carrier family, Vgat), the transmembrane transporters Slc6a1 (Gat1) and Slc6a11 (Gat3) was assessed by semiquantitative radioactive in situ hybridization. APZ treatment resulted in time- and dose-dependent effects with qualitative differences between brain regions. In the 10-mg group, Slc6a1 was strongly induced after 4 weeks in the hippocampus, amygdala, and cerebral cortex, followed by an induction of Gad67 in the same regions after 4 months, while frontocortical regions as well as basal ganglia showed dose-dependent reductions of Gad67 expression after 4 months. In several frontocortical and subcortical regions, we observed a decrease of Slc32a1 and an increase of Slc6a11 expression. In conclusion, APZ modulates gene expression of GABAergic marker genes involved into pathogenetic theories of schizophrenia. APZ only partially mirrors the effects of other antipsychotics with some important differences regarding brain regions. The findings might be explained by regulatory connections between serotonergic, GABAergic, and dopaminergic neurotransmission and should be validated in behavioral animal models of psychotic disorders.

Do tardive dyskinesia and L-dopa induced dyskinesia share common genetic risk factors? An exploratory study

Tardive dyskinesia (TD) in schizophrenia patients treated with antipsychotic medications and L-dopa induced dyskinesia (LID) among Parkinson's disease (PD) affected individuals share similar clinical features. Both conditions are induced by chronic exposure to drugs that target dopaminergic receptors (antagonists in TD and agonists in LID) and cause pulsatile and nonphysiological stimulation of these receptors. We hypothesized that the two motor adverse effects partially share genetic risk factors such that certain genetic variants exert a pleiotropic effect, influencing susceptibility to TD as well as to LID. In this pilot study, we focused on 21 TD-associated SNPs, previously reported in TD genome-wide association studies or in candidate gene studies. By applying logistic regression and controlling for relevant clinical risk factors, we studied the association of the SNPs with LID vulnerability in two independent pharmacogenetic samples. We included a Jewish Israeli sample of 203 PD patients treated with L-dopa for a minimum of 3 years and evaluated the existence or absence of LID (LID+ = 128; LID- = 75). An Italian sample was composed of early LID developers (within the first 3 years of treatment, N = 187) contrasted with non-early LID developers (after 7 years or more of treatment, N = 203). None of the studied SNPs were significantly associated with LID susceptibility in the two samples. Therefore, we were unable to obtain proof of concept for our initial hypothesis of an overlapping contribution of genetic risk factors to TD and LID. Further studies in larger samples are required to reach definitive conclusions.

Treatment of neurolept-induced tardive dyskinesia

Tardive dyskinesia (TDK) includes orobuccolingual movements and "piano-playing" movements of the limbs. It is a movement disorder of delayed onset that can occur in the setting of neuroleptic treatment as well as in other diseases and following treatment with other drugs. The specific pathophysiology resulting in TDK is still not completely understood but possible mechanisms include postsynaptic dopamine receptor hypersensitivity, abnormalities of striatal gamma-aminobutyric acid (GABA) neurons, and degeneration of striatal cholinergic interneurons. More recently, the theory of synaptic plasticity has been proposed. Considering these proposed mechanisms of disease, therapeutic interventions have attempted to manipulate dopamine, GABA, acetylcholine, norepinephrine and serotonin pathways and receptors. The data for the effectiveness of each class of drugs and the side effects were considered in turn.

Relationship between dose, drug levels, and D2 receptor occupancy for the atypical antipsychotics risperidone and paliperidone

Blockade of D2 family dopamine receptors (D2Rs) is a fundamental property of antipsychotics, and the degree of striatal D2R occupancy has been related to antipsychotic and motor effects of these drugs. Recent studies suggest the D2R occupancy of antipsychotics may differ in extrastriatal regions compared with the dorsal striatum. We studied this issue in macaque monkeys by using a within-subjects design. [(18)F]fallypride positron emission tomography scans were obtained on four different doses of risperidone and paliperidone (the 9-OH metabolite of risperidone) and compared with multiple off-drug scans in each animal. The half-life of the two drugs in these monkeys was determined to be between 3 and 4 h, and drug was administered by a constant infusion through an intragastric catheter. The D2R occupancy of antipsychotic was determined in the caudate, putamen, ventral striatum, and four prefrontal and temporal cortical regions and was related to serum and cerebrospinal fluid drug levels. Repeated 2-week treatment with risperidone or paliperidone did not produce lasting changes in D2R binding potential in any region examined. As expected, D2R binding potential was highest in the caudate and putamen and was approximately one-third that level in the ventral striatum and 2% of that level in the cortical regions. We found dose-dependent D2R occupancy for both risperidone and paliperidone in both basal ganglia and cortical regions of interest. We could not find evidence of regional variation in D2R occupancy of either drug. Comparison of D2R occupancy and serum drug levels supports a target of 40 to 80 ng/ml active drug for these two atypical antipsychotics.

Support for association of HSPG2 with tardive dyskinesia in Caucasian populations

Tardive dyskinesia (TD) is a severe adverse effect of chronic antipsychotic drug treatment. In addition to clinical risk factors, TD susceptibility is influenced by genetic predisposition. Recently, Syu et al. (2010) reported a genome-wide association screening of TD in Japanese schizophrenia patients. The best result was association of single-nucleotide polymorphism (SNP) rs2445142 in the HSPG2 (heparan sulfate proteoglycan 2) gene with TD. In the present study, we report a replication study of the five top Japanese TD-associated SNPs in two Caucasian TD samples. Applying logistic regression and controlling for relevant clinical risk factors, we were able to replicate the association of HSPG2 SNP rs2445142 with TD in a prospective study sample of 179 Americans of European origin by performing a secondary analysis of the CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness) genome-wide association study data set, and using a perfect proxy surrogate marker (rs878949; P = 0.039). An association of the 'G' risk allele of HSPG2 SNP rs2445142 with TD was also shown in a sample of Jewish Israeli schizophrenia patients (retrospective, cross-sectional design; P = 0.03). Although the associations were only nominally significant, the findings provide further support for the possible involvement of HSPG2 in susceptibility to TD.

Anterior internal capsule volumes increase in patients with schizophrenia switched from typical antipsychotics to olanzapine

Abnormalities in connectivity are thought to contribute to the symptoms of schizophrenia. Accumulating evidence suggests that antipsychotic medication affects both subcortical and cortical grey and white matter volumes. The goal of this study was to investigate the effects of antipsychotic medication on two white matter tracts: a subcortical-cortical tract, the anterior and posterior limbs of the internal capsule; and a cortical-cortical tract, the corpus callosum. Magnetic resonance imaging was conducted on 10 chronic schizophrenia patients treated with typical antipsychotics and 20 healthy controls at baseline. Patients were switched to olanzapine and both groups were rescanned after 1 year. At baseline, the volume of the anterior limb of the internal capsule was 24% smaller in typical-treated patients than controls (p = 0.009). Patients treated with greater amounts of chlorpromazine-equivalent daily dosage had smaller anterior internal capsule volumes at baseline (r = -0.65, p = 0.04). At follow-up, after being switched to olanzapine, there were no significant differences between patients and controls. Patients with schizophrenia had a significant 25% increase in anterior internal capsule volume from baseline to follow-up compared with controls (p = 0.04). These effects were most prominent in the anterior limb of the internal capsule, which consists of fronto-thalamic pathways, and were not statistically significant in the posterior limb of the internal capsule or corpus callosum. Olanzapine may be effective in normalizing fronto-thalamic structural connectivity in schizophrenia.

Divergent acute and chronic modulation of glutamatergic postsynaptic density genes expression by the antipsychotics haloperidol and sertindole

RATIONALE

A pivotal role for glutamate in the pathophysiology and treatment of schizophrenia has been suggested. Few reports have investigated the impact of antipsychotics on postsynaptic density (PSD) molecules involved in glutamatergic transmission and synaptic remodeling. Homer is a key PSD molecule putatively implicated in schizophrenia.

OBJECTIVES

We studied the effect, in acute and chronic paradigms, of a first and a second generation antipsychotic (haloperidol and sertindole, respectively) on the expression of Homer1a and Homer-interacting PSD molecules.

RESULTS

In the acute paradigm, Homer1a expression was induced by haloperidol but not sertindole in the striatum, consistent with the less propensity of sertindole to affect nigrostriatal neurotransmission. The profile of expression of two other inducible genes, Ania3 and Arc, was highly similar to Homer1a. In the cortex, haloperidol reduced Homer1a and induced Ania3. In the chronic paradigm, striatal expression of Homer1a and Ania3 resembled that observed in the acute paradigm. In the cortex, haloperidol induced Homer1a, while sertindole did not. Homer1b expression was increased by haloperidol in the striatum and cortex whereas sertindole selectively induced Homer1b in the cortex. The expression of mGluR5 was increased by both antipsychotics. A modulation by haloperidol was also seen for PSD-95 and αCaMKII.

CONCLUSIONS

These results suggest that haloperidol and sertindole may significantly modulate glutamatergic transcripts of the postsynaptic density. Sertindole induces constitutive genes in the cortex predominantly, which may correlate with its propensity to improve cognitive functions. Haloperidol preferentially modulates gene expression in the striatum, consistent with its action at nigrostriatal projections and its propensity to give motor side effects.

GABA concentration in schizophrenia patients and the effects of antipsychotic medication: a proton magnetic resonance spectroscopy study

Gamma-amino butyric acid (GABA) is thought to play a role in the pathophysiology of schizophrenia. High magnetic field proton magnetic resonance spectroscopy ((1)H-MRS) provides a reliable measurement of GABA in specific regions of the brain. This study measured GABA concentration in the anterior cingulate cortex (ACC) and in the left basal ganglia (ltBG) in 38 patients with chronic schizophrenia and 29 healthy control subjects. There was no significant difference in GABA concentration between the schizophrenia patients and the healthy controls in either the ACC (1.36+/-0.45 mmol/l in schizophrenia patients and 1.52+/-0.54 mmol/l in control subjects) or the ltBG (1.13+/-0.26 mmol/l in schizophrenia patients and 1.18+/-0.20 mmol/l in control subjects). Among the right handed schizophrenia patients, the GABA concentration in the ltBG was significantly higher in patients taking typical antipsychotics (1.25+/-0.24 mmol/l) than in those taking atypical antipsychotics (1.03+/-0.24 mmol/l, p=0.026). In the ACC, the GABA concentration was negatively correlated with the dose of the antipsychotics (rs=-0.347, p=0.035). In the ltBG, the GABA concentration was positively correlated with the dose of the anticholinergics (rs=0.403, p=0.015). To the best of our knowledge, this is the first study to have directly measured GABA concentrations in schizophrenia patients using (1)H-MRS. Our results suggest that there are no differences in GABA concentrations in the ACC or the ltBG of schizophrenia patients compared to healthy controls. Antipsychotic medication may cause changes in GABA concentration, and atypical and typical antipsychotics may have differing effects. It is possible that medication effects conceal inherent differences in GABA concentrations between schizophrenia patients and healthy controls.

Chronic psychotropic drug treatment causes differential expression of Reelin signaling system in frontal cortex of rats

Disruption of the Reelin and GABAergic signaling systems have been observed in psychiatric disorders including autism, schizophrenia, bipolar disorder, and major depression. Less is known of therapeutic interventions that may help ameliorate the effects of these disruptions. The current study investigated whether chronic administration of psychotropic medications (clozapine, fluoxetine, haloperidol, lithium, olanzapine, and valproic acid) used in the treatment of psychiatric disorders alters levels of Reelin, its receptor Vldlr, downstream molecules Gsk3 beta, Dab-1, and Gad65/67 in rat prefrontal cortex as measured by qRT-PCR and SDS-PAGE and western blotting. qRT-PCR revealed that mRNAs for Reelin, Vldlr, Dab-1, Gsk3 beta, and Gad65 were each significantly altered by at least one of the drugs tested, and in the case of Reelin, Dab-1, and Gsk3 beta, by multiple drugs. To verify our results, we also performed SDS-PAGE and western blotting experiments. Again, several of the protein products for Reelin, Vldlr, Dab-1, Gsk3 beta, Gad65, and Gad67 were also significantly altered by multiple drugs. The present results suggest that the Reelin signaling and GABAergic systems are affected by commonly used psychotropic medications. These changes may help explain the efficacy of these drugs and provide further support for the investigation of the Reelin and GABAergic signaling systems as therapeutic targets for the treatment of neuropsychiatric diseases.

The neonatal ventral hippocampal lesion as a heuristic neurodevelopmental model of schizophrenia

Traditionally, animal models of schizophrenia were predominantly pharmacological constructs focused on phenomena linked to dopamine and glutamate neurotransmitter systems, and were created by direct perturbations of these systems. A number of developmental models were subsequently generated that allowed testing of hypotheses about the origin of the disease, mimicked a wider array of clinical and neurobiological features of schizophrenia, and opened new avenues for developing novel treatment strategies. The most thoroughly characterized (approximately 100 primary research articles) is the neonatal ventral hippocampal lesion (NVHL) model, which is the subject of this review. We highlight its advantages and limitations, and how it may offer clues about the extent to which positive, negative, cognitive, and other aspects of schizophrenia, including addiction vulnerability, represent inter-related pathophysiological mechanisms.

Neuroleptics and animal models: feasibility of oral treatment monitored by plasma levels and receptor occupancy assays

The administration of neuroleptics in animal models has been extensively reported and plays an important role in the study of schizophrenia. Our study was designed to address the following questions: (1) Is it possible to achieve steady-state receptor occupancy levels administering neuroleptics in drinking water? (2) Is there an appropriate dose to obtain clinically comparable receptor occupancies? (3) Is there a correlation between plasma drug levels and receptor occupancy? Thus, we tested three neuroleptic drugs administered in drinking water for 7 days. Plasma drug levels were measured, and in vivo receptor occupancy assays were performed in order to determine peak and trough dopamine D(2) receptor occupancies in striatal brain samples. Overall, our study indicates that in rodents the administration of appropriate doses of haloperidol and olanzapine in drinking water achieves receptor occupancies comparable to the clinical occupancy levels, but this appears not to be the case for clozapine.

Molecular and cellular mechanisms of altered GAD1/GAD67 expression in schizophrenia and related disorders

The 67 and 65 kDa isoforms of glutamic acid decarboxylase, the key enzymes for GABA biosynthesis, are expressed at altered levels in postmortem brain of subjects diagnosed with schizophrenia and related disorders, including autism and bipolar illness. The predominant finding is a decrease in GAD67 mRNA levels, affecting multiple brain regions, including prefrontal and temporal cortex. Postmortem studies, in conjunction with animal models, identified several mechanisms that contribute to the dysregulation of GAD67 in cerebral cortex. These include disordered connectivity formation during development, abnormal expression of Reelin and neural cell adhesion molecule (NCAM) glycoproteins, defects in neurotrophin signaling and alterations in dopaminergic and glutamatergic neurotransmission. These mechanisms are likely to operate in conjunction with genetic risk factors for psychosis, including sequence polymorphisms residing in the promoter of GAD1 (2q31), the gene encoding GAD67. We propose an integrative model, with multiple molecular and cellular mechanisms contributing to transcriptional dysregulation of GAD67 and cortical dysfunction in psychosis.

An influence of ligands of metabotropic glutamate receptor subtypes on parkinsonian-like symptoms and the striatopallidal pathway in rats

Several data indicate that inhibition of glutamatergic transmission may be important to alleviate of parkinsonian symptoms. Therefore, the aim of the present paper is to review recent studies on the search for putative antiparkinsonian-like effects of mGluR ligands and their brain targets. In order to inhibit glutamatergic transmission, the group I mGluRs (mGluR1 and mGluR5) were blocked, and group II (mGluR2/3) or III (mGluR4/7/8) mGluRs were activated. Systemic or intrastriatal administration of group I mGluR antagonists (mGluR5 - MPEP, MTEP; mGluR1 - AIDA) was found to inhibit parkinsonian-like symptoms (catalepsy, muscle rigidity) in rats. MPEP administered systemically and mGluR1 antagonists (AIDA, CPCCOEt, LY367385) injected intrastriatally reversed also the haloperidol-increased proenkephalin (PENK) mRNA expression in the striatopallidal pathway. Similarly, ACPT-1, a group III mGluR agonist, administered into the striatum, globus pallidus or substantia nigra inhibited the catalepsy. Intrastriatal injection of this compound reduced the striatal PENK expression induced by haloperidol. In contrast, a group II mGluR agonist (2R,4R-APDC) administered intrastriatally reduced neither PENK expression nor the above-mentioned parkinsonian-like symptoms. Moreover, a mixed mGluR8 agonist/AMPA antagonist, (R,S)-3,4-DCPG, administered systemically evoked catalepsy and enhanced both the catalepsy and PENK expression induced by haloperidol. The results reviewed in this article seem to indicate that group I mGluR antagonists or some agonists of group III may possess antiparkinsonian properties, and point at the striatopallidal pathway as a potential target of therapeutic intervention.

Dysregulation of thalamic sensory "transmission" in schizophrenia: neurochemical vulnerability to hallucinations

Cholinergic arousal mechanisms predispose thalamic and cortical neurons to fire action potentials at gamma rhythms, which have a tendency to resonate in thalamocortical networks, thereby forming coherent assemblies under constraints of sensory input to specific thalamic nuclei, on the one hand, and prefrontal and limbic attentional mechanisms, on the other. Perception may be based on sustained assemblies of coherent gamma oscillations in thalamocortical circuits. In schizophrenia, the impact of sensory input on self-organization of thalamocortical activity may be generally reduced. As a result, processes underlying perception can become uncoupled from sensory input, particularly at times of hyperarousal, leading to domination of attentional mechanisms and the emergence of hallucinations. Evidence is reviewed that implicates excessive neuronal noise in specific thalamic nuclei in the generation of hallucinations in schizophrenia. Nicotinic receptor abnormalities, dopaminergic hyperactivity and glutamate-receptor hypofunction are reconciled within a model of psychotic symptom generation that places crucial emphasis on dysfunction of the reticular thalamic nucleus.

Magnetic resonance spectroscopic measurement of cerebral gamma-aminobutyric acid concentrations in patients with bipolar disorders

BACKGROUND

Animal models of depression and psychopharmacological mechanisms of action suggest the importance of the gamma-amino butyric acid (GABA) system in the pathophysiology of mood disorders. Mood stabilizers have overlapping effects on GABAergic neurotransmission, and antidepressant use has been associated with alterations in GABAB receptor function. Magnetic resonance spectroscopy (MRS) provides an opportunity to noninvasively assess cerebral GABA concentrations in anterior paralimbic circuits that have been implicated in mood disorders.

METHODS

In bipolar disorder patients and healthy control subjects, we used MRS with a modified GABA-edited point resolved spectroscopy sequence (TE 68 ms, TR 1500 ms, 512 averages, total scan time 26 min) to assess GABA in an 18-cm3 occipital voxel. In addition, in another cohort of bipolar disorder patients and healthy control subjects, we similarly assessed GABA in a 12.5-cm3 medial prefrontal/anterior cingulate (MPF/AC) voxel. The concentration of GABA was referenced to creatine (Cr) from unedited spectra.

RESULTS

In bipolar patients and controls, we consistently detected 3.0 p.p.m. GABA peaks in occipital lobe and MPF/AC. In 16 bipolar (nine bipolar I and seven bipolar II) disorder patients, compared with six healthy control subjects, mean occipital GABA/Cr concentration was 61% higher. In addition, in 15 bipolar (five bipolar I, nine bipolar II, and one bipolar not otherwise specified) disorder patients, compared with six healthy control subjects, mean MPF/AC GABA/Cr concentration tended to be 41% higher.

CONCLUSIONS

Patients with bipolar disorders may have increased cerebral GABA concentrations. Although this was more evident in the occipital lobe, MPC/AC GABA disturbance may be of greater potential interest in view the more established role of MPF/AC in affective processing. Additional studies are warranted to assess changes in GABAergic neurotransmission and the influences of diagnosis, mood state, and medication status in bipolar disorder patients.

Subchronic haloperidol increases CB(1) receptor binding and G protein coupling in discrete regions of the basal ganglia

The present study was designed to test whether chronic neuroleptic treatment, which is known to alter both expression and density of dopamine D(2) receptors in striatal regions, has effects upon function and binding level of the cannabinoid CB(1) receptor in the basal ganglia by using receptor autoradiography. As predicted, subchronic haloperidol treatment resulted in increased binding of (3)H-raclopride and quinpirole-induced guanosine 5'-O-(gamma-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) in the striatum when compared to that measured in control animals. This increased D(2) receptor binding and function after 3 days washout was normalized after a 2-week washout period. Effect of haloperidol treatment was studied for CB(1) receptor binding and CP55,940-stimulated [(35)S]GTPgammaS in the striatum, globus pallidus, and substantia nigra. (3)[H]CP55,940 binding levels were found in rank order from highest to lowest in substantia nigra > globus pallidus > striatum. Furthermore, subchronic haloperidol treatment resulted in elevated binding levels of (3)[H]CP55,940 in the striatum and the substantia nigra and CB(1) receptor-stimulated [(35)S]GTPgammaS bindings in the substantia nigra after 3 days washout. These increased binding levels were normalized at 1-4 weeks after termination of haloperidol treatment. Haloperidol treatment had no significant effect on CB(1) receptor or [(35)S]GTPgammaS binding levels in globus pallidus. The results help to elucidate the underlying biochemical mechanism of CB(1) receptor supersensitivity after haloperidol treatment.

Antipsychotic pathway genes with expression altered in opposite direction by antipsychotics and amphetamine

To develop a new strategy for identifying possible psychotic- or antipsychotic-related pathway genes, rats were treated with clinical doses of haloperidol and clozapine for 4 days, and the altered expression of genes was compared with the genes altered in expression after amphetamine sensitization. The objective was to identify genes with expression altered in the same direction by haloperidol and clozapine but in the opposite direction in the amphetamine-sensitized rat striatum. These criteria were met by 21 genes, consisting of 15 genes upregulated by amphetamine, and 6 genes downregulated by amphetamine. Of the 21 genes, 15 are not presently identified, and only 3 genes (cathepsin K, GRK6, and a gene with accession number AI177589) are located in chromosome regions known to be associated with schizophrenia.

Positive association of the human GABA-A-receptor beta 2 subunit gene haplotype with schizophrenia in the Chinese Han population

A converging body of evidence implicates the gamma-amino butyric acid neurotransmitter system in the pathogenesis of schizophrenia. Recently, Lo et al. reported strong positive association between schizophrenia and GABRB2, demonstrated by single markers and haplotypes of five markers in introns of GABRB2, rs6556547, rs1816071, rs194072, rs252944, and rs187269. To validate this linkage disequilibrium report, we genotyped these five SNPs and additional rs1816072 in 352 Chinese Han family trios. Though we failed to detect any positive results in single markers, we did find a significant haplotypic association (global p = 0.00157-0.00588) which had not been identified in Lo's study. Our data indicated that the haplotype 'GACTCT' (p = 0.00215, frequency = 53.6%) was overtransmitted which suggests that GABRB2 is in linkage disequilibrium with schizophrenia in the Chinese Han population. The difference between the two studies may be due to the respective analytic power of the two designs. These two independent studies highlighting linkage disequilibrium support the potential involvement of GABRB2 or a nearby gene in the genetic etiology of schizophrenia.

Different effects of typical and atypical antipsychotics on grey matter in first episode psychosis: the AESOP study

Typical antipsychotic drugs act on the dopaminergic system, blocking the dopamine type 2 (D2) receptors. Atypical antipsychotics have lower affinity and occupancy for the dopaminergic receptors, and a high degree of occupancy of the serotoninergic receptors 5-HT2A. Whether these different pharmacological actions produce different effects on brain structure remains unclear. We explored the effects of different types of antipsychotic treatment on brain structure in an epidemiologically based, nonrandomized sample of patients at the first psychotic episode. Subjects were recruited as part of a large epidemiological study (AESOP: aetiology and ethnicity in schizophrenia and other psychoses). We evaluated 22 drug-free patients, 32 on treatment with typical antipsychotics and 30 with atypical antipsychotics. We used high-resolution MRI and voxel-based methods of image analysis. The MRI analysis suggested that both typical and atypical antipsychotics are associated with brain changes. However, typicals seem to affect more extensively the basal ganglia (enlargement of the putamen) and cortical areas (reductions of lobulus paracentralis, anterior cingulate gyrus, superior and medial frontal gyri, superior and middle temporal gyri, insula, and precuneus), while atypical antipsychotics seem particularly associated with enlargement of the thalami. These changes are likely to reflect the effect of antipsychotics on the brain, as there were no differences in duration of illness, total symptoms scores, and length of treatment among the groups. In conclusion, we would like to suggest that even after short-term treatment, typical and atypical antipsychotics may affect brain structure differently.

Differences in the cellular distribution of D1 receptor mRNA in the hippocampus of bipolars and schizophrenics

Several lines of evidence have pointed to a role of the dopamine system in the pathophysiology of schizophrenia. A recent postmortem study demonstrated a selective decrease of tyrosine hydroxylase fibers on pyramidal neurons in sector CA2 in the hippocampus of schizophrenics. Although both brain imaging and postmortem studies have examined the distribution of the D1 receptor in the prefrontal and cingulate cortex, no study to date has examined its expression of mRNA using a high-resolution autoradiographic approach. In order to further assess whether the regulation of the dopamine D1 receptor is altered in hippocampal neurons in this disorder, we used in situ hybridization (ISH) to measure the expression of messenger RNA for this receptor in the dentate gyrus and sectors CA1-4. Both the number of cells expressing D1 mRNA and the amount of expression per cell were measured in 15 schizophrenic, 15 bipolar disorder, and 15 normal control subjects. The results show a significant (21%) and selective decrease in D1 mRNA expression in sector CA3 of schizophrenic subjects. First-degree relatives of schizophrenics did not show any differences in either the expression of D1 mRNA per cell or the number of cells expressing this mRNA when compared to a separate group of normal controls matched for age and PMI. Subjects with bipolar disorder also showed a significant (25%) and selective increase of D1 mRNA expression in sector CA2. Other hippocampal sectors did not show significant changes. These findings in schizophrenics and bipolars were also associated with inverse changes in the overall number of neurons expressing D1 mRNA in sectors CA3 and CA2, respectively. This study shows diagnosis-specific changes in D1 mRNA expression in the hippocampus of schizophrenic versus bipolar subjects and suggests that this neuromodulatory system may show distinct changes in the pathophysiology of the two disorders.

Cognitive factors in schizophrenia: causes, impact, and treatment

Greater attention has been given to the cognitive dimension in schizophrenia in recent years. This has resulted from increased recognition that cognitive impairment and negative symptoms of the disease have a greater impact on quality of life (QOL) compared to positive symptoms. Successful treatment of positive symptoms in patients with schizophrenia has not been shown to robustly translate into improvements in employment status or social relationships, while cognitive improvements are strongly associated with these important aspects of QOL and independence. These findings are based on extensive testing with standard cognitive tests for measuring executive function, verbal learning and memory, word recall, verbal working memory, spatial working memory, attention, and vigilance. Verbal learning and executive function, in particular, have been found to be valid predictors of employment success independent of the degree of severity of positive symptoms.

Olanzapine treatment for tardive dyskinesia in schizophrenia patients: a prospective clinical trial with patients randomized to blinded dose reduction periods

BACKGROUND

Tardive dyskinesia (TD) is a potentially persistent and disabling abnormal involuntary movement disorder. The aim of this 8-month study was to determine if olanzapine treatment could lead to a significant and persistent reduction in preexisting TD.

METHODS

Eligible schizophrenia patients met restricted Research Diagnosis criteria of TD requiring, in part, a rating of at least moderate severity (score > or = 3) in one or more of seven body regions on the Abnormal Involuntary Movement Scale (AIMS). Patients received olanzapine, 5-20 mg/day, for 8 months. During this period, they underwent one to two dose reduction periods under blinded conditions. Concurrent changes in TD, psychopathology, parkinsonism and akathisia were assessed with the AIMS, the Positive and Negative Syndrome Scale (PANSS), and the Simpson-Angus and Barnes Akathisia Scales, respectively.

RESULTS

A significant reduction in mean AIMS total score was demonstrated at endpoint (n = 92; p < 0.001) as well as at each visit (p < 0.001) and as early as Week 1 on olanzapine. Approximately 70% of patients no longer met the restricted Research Diagnostic criteria for persistent TD (RD-TD) after 8 months of treatment. No statistically significant rebound worsening of TD was found during either blinded drug reduction period. Significant improvement in psychopathology (p = 0.001) and parkinsonism (p < 0.001) was observed.

CONCLUSIONS

Improvement in the severity of preexisting TD was achieved with olanzapine and persisted throughout the 8-month study and during each dose reduction period. Overall improvement in clinical status suggests that olanzapine may be effective for the long-term management of schizophrenia patients with preexisting TD.

Differential effects of long-term treatment with clozapine or haloperidol on GABAA receptor binding and GAD67 expression

One of the most consistent findings in postmortem studies of schizophrenia is increased GABAA receptor binding and reduced glutamic acid decarboxylase (GAD67) expression. Due to long-term antipsychotic treatment before death, these findings may reflect not only the consequences of schizophrenia but also medication effects. To differentiate between these options, we used an animal model and evaluated long-term effects of typical (haloperidol) and atypical (clozapine) antipsychotic drugs on the GABAergic system. A total of 33 adult male rats were treated in three cohorts over a period of 6 months. One cohort of 11 animals received clozapine (45 mg/kg/day), another one received haloperidol (1.5 mg/kg/day) and a third one received pH-adapted minimal concentrations of HCl in the drinking water. Receptor autoradiography of the GABAA receptor ([3H]-muscimol binding) and in situ hybridization in adjacent sections with 35S-labeled cRNA probes of the y-aminobutyric acid (GABA)-producing enzyme, GAD67, was performed. While haloperidol increased GABAA receptor binding in striatum and nucleus accumbens (NA), it suppressed GABAA receptor binding in temporal (TEMPC) and parietal (PARC) cortex. Clozapine induced GABAA receptor binding in infralimbic cortex (ILC) and similar like haloperidol in anterior cingulate cortex (ACC), two regions of the limbic cortex. In addition, either drug increased gene expression of GAD67. It is concluded that antipsychotic drugs differentially alter the GABAergic system, strongly suggesting that drug effects are partially responsible for the up-regulation of GABAA receptor binding in certain brain regions as observed in postmortem brains of schizophrenic patients. However, the reduced GAD67 expression seen in postmortem brains does not appear to reflect drug effects, since our animal model demonstrated increased gene expression.

GABA and schizophrenia: a review of basic science and clinical studies

BACKGROUND

A converging body of evidence implicates the gamma-aminobutyric acid (GABA) neurotransmitter system in the pathogenesis of schizophrenia.

METHODS

The authors review neuroscience literature and clinical studies investigating the role of the GABA system in the pathophysiology of schizophrenia. First, a background on the GABA system is provided, including GABA pharmacology and neuroanatomy of GABAergic neurons. Results from basic science schizophrenia animal models and human studies are reviewed. The role of GABA in cognitive dysfunction in schizophrenia is then presented, followed by a discussion of GABAergic compounds used in monotherapy or adjunctively in clinical schizophrenia studies.

RESULTS

In basic studies, reductions in GABAergic neuronal density and abnormalities in receptors and reuptake sites have been identified in several cortical and subcortical GABA systems. A model has been developed suggesting GABA's role (including GABA-dopamine interactions) in schizophrenia. In several clinical studies, the use of adjunctive GABA agonists was associated with greater improvement in core schizophrenia symptoms.

CONCLUSIONS

Alterations in the GABA neurotransmitter system are found in clinical and basic neuroscience schizophrenia studies as well as animal models and may be involved in the pathophysiology of schizophrenia. The interaction of GABA with other well-characterized neurotransmitter abnormalities remains to be understood. Future studies should elucidate the potential therapeutic role for GABA ligands in schizophrenia treatment.

Differential effects of antipsychotics on haloperidol-induced vacuous chewing movements and subcortical gene expression in the rat

The behavioral and neurochemical effects of switching from typical to atypical medications have not been evaluated in the rodent models of tardive dyskinesia. Thus, we treated rats with haloperidol-decanoate for 12 weeks, and assessed the effects of additional treatment with olanzapine, haloperidol, clozapine, or vehicle on vacuous chewing movements and expression of transcripts for dopamine receptors, tyrosine hydroxylase, delta-opioid receptor, prodynorphin, preproenkephalin, glutamic acid decarboxylase-65 (glutamic acid decarboxylase (GAD)-65) and GAD-67 and N-methyl-D-aspartate (NMDA) receptor subunits in the striatum and its efferent pathways. Haloperidol-decanoate induced vacuous chewing movements extinguished following an additional 4 weeks of treatment with vehicle, olanzapine or haloperidol, but not clozapine. Post-treatment, vacuous chewing movements in the clozapine group were significantly higher than the vehicle, olanzapine and haloperidol groups. GAD-67 mRNA expression in the globus pallidus was decreased following additional treatment with olanzapine or haloperidol, but not clozapine. Changes in expression of other transcripts were not detected. These findings demonstrate important differences in the effects of typical and atypical antipsychotics on chronic vacuous chewing movements.

Hallucinations: synchronisation of thalamocortical gamma oscillations underconstrained by sensory input

What we perceive is the product of an intrinsic process and not part of external physical reality. This notion is consistent with the philosophical position of transcendental idealism but also agrees with physiological findings on the thalamocortical system. gamma-Frequency rhythms of discharge activity from thalamic and cortical neurons are facilitated by cholinergic arousal and resonate in thalamocortical networks, thereby transiently forming assemblies of coherent gamma oscillations under constraints of sensory input and prefrontal attentional mechanisms. Perception and conscious experience may be based on such assemblies and sensory input to thalamic nuclei plays merely a constraining role in their formation. In schizophrenia, the ability of sensory input to modulate self-organisation of thalamocortical gamma activity may be generally reduced. If during arousal thalamocortical self-organisation is underconstrained by sensory input, then attentional mechanisms alone may determine the content of perception and hallucinations may arise.

Antipsychotic drug-induced movement disorders

Very early in the process of diagnosing abnormal involuntary movement (AIM) disorders, one can be rewarded by keeping a high index of suspicion for possible drug-induced causes, not only through a complete list of current medications, but also identification of the drugs the patient used to take and other possible offending medications that might be available from family members and other sources. Among drug-induced movement disorders, antipsychotic drugs and other dopamine receptor blocking agents occupy a central place. Their various acute and tardive motor complications provide the template of this short review. Movement disorders caused by antidepressants, lithium, antiemetics, antiparkinsonian agents, anticonvulsants, calcium channel blockers, sympathomimetics and others are only briefly covered in table form.

The role of metabotropic glutamate receptors in regulation of striatal proenkephalin expression: implications for the therapy of Parkinson′s disease

Overactivity of the striatopallidal pathway, associated with an enhancement of enkephalin expression, has been suggested to contribute to the development of parkinsonian symptoms. The aim of the present study was to examine whether the blockade of group I metabotropic glutamate receptors: subtypes 1 and 5 (mGluR1/5), or stimulation of group II: subtypes 2 and 3 (mGluR2/3) may normalize enkephalin expression in the striatopallidal pathway in an animal model of parkinsonism. The proenkephalin mRNA level measured by in situ hybridization in the striatum was increased by pretreatments with haloperidol (1.5 mg/kg s.c., three times, 3 h apart). Triple (3 h apart), bilateral, intrastriatal administration of selective antagonists of mGluR1: (S)-(+)-alpha-amino-4-carboxy-2-methylbenzeneacetic acid (3 x 5 microg/0.5 microl) or 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate (3 x 2.5 microg/0.5 microl), reversed the haloperidol-induced increases in proenkephalin mRNA levels in the rostral and central regions of the striatum. Similarly, repeated (6 times, 1.5 h apart), systemic injections of an antagonist of mGluR5, 2-methyl-6-(phenylethynyl)pyridine (6 x 10 mg/kg i.p.) counteracted an increase in the striatal proenkephalin mRNA expression elicited by haloperidol. None of the abovementioned antagonists of mGluR1 and mGluR5 per se influenced the proenkephalin expression. Differential effects were induced by agonists of the group II mGluRs, viz. (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine administered intraventricularly (3 times at 0.1-0.2 microg/4 microl, 3 h apart) increased both the normal and haloperidol-increased proenkephalin mRNA level, whereas (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate injected intrastriatally (3 times at 15 microg/0.5 microl, 3 h apart) was ineffective. The present study indicates that the blockade of striatal glutamate receptors belonging to the group I (mGluR1 and mGluR5) but not stimulation of the group II mGluRs may normalize the function of the striatopallidal pathway in an animal model of parkinsonism, which may be important for future antiparkinsonian therapy in humans.

Molecular abnormalities in the major psychiatric illnesses: Classification and Regression Tree (CRT) analysis of post-mortem prefrontal markers

Post-mortem specimens from the Stanley Foundation Neuropathology Consortium, which contains matched samples from patients with schizophrenia, bipolar disorder, non-psychotic depression and normal controls (n = 15 per group), have been distributed to many research groups around the world. This paper provides a summary of abnormal markers found in prefrontal cortical areas from this collection between 1997 and 2001. With parametric analyses of variance of 102 separate data sets, 14 markers were abnormal in at least one disease. The markers pertained to a variety of neural systems and processes including neuronal plasticity, neurotransmission, signal transduction, inhibitory interneuron function and glial cells. The data sets were also examined using the non-parametric Classification and Regression Tree (CRT) technique for the four diagnostic groups and in pair-wise combinations. In contrast to the results obtained with analyses of variance, the CRT method identified a smaller set of nine markers that contributed maximally to the diagnostic classifications. Three of the nine markers observed with CRT overlapped with the ANOVA results. Six of the nine markers observed with the CRT technique pertained to aspects of glutamatergic, GABA-ergic, and dopaminergic neurotransmission.

Sub-chronic treatment with classical but not atypical antipsychotics produces morphological changes in rat nigro-striatal dopaminergic neurons directly related to "early onset" vacuous chewing

In the present work, we investigated if an impairment of dopaminergic neurons after subchronic haloperidol treatment might be a possible physiopathologic substrate of the "early onset" vacuous chewing movements (VCMs) in rats. For this purpose, different antipsychotics were used to analyse a possible relationship between VCMs development and morphological alterations of tyrosine-hydroxylase-immunostained (TH-IM) neurons. Rats treated twice a day with haloperidol displayed a significant increase of VCMs that was both time- (2-4 weeks) and dose (0.1-1 mg/kg) dependent. Immunocytochemical analysis showed a shrinkage of TH-IM cell bodies in substantia nigra pars compacta and reticulata and a reduction of TH-immunostaining in the striatum of haloperidol treated rats with the arising of VCMs. No differences were observed in TH-IM neurons of ventral tegmental area and nucleus accumbens vs. control rats. The atypical antipsychotics risperidone (2 mg/kg, twice a day), amisulpride (20 mg/kg, twice a day) and clozapine (10 mg/kg, twice a day) did not produce any nigro-striatal morphological changes or VCMs. TH-IM nigro-striatal neuron morphological alterations and VCMs were still present after three days of withdrawal in rats treated for four weeks with haloperidol (1 mg/kg). Both the main morphological changes and the behavioural correlate disappeared after three weeks of withdrawal. These results suggest that haloperidol induces a morphological impairment of the dopaminergic nigro-striatal neurons which is directly associated with the arising, permanency and disappearance of VCMs in rats.