Brain gamma-aminobutyric acid abnormality in tardive dyskinesia. Reduction in cerebrospinal fluid GABA levels and therapeutic response to GABA agonist treatment

A novel giant non-cholinergic striatal interneuron restricted to the ventrolateral striatum coexpresses Kv3.3 potassium channel, parvalbumin, and the vesicular GABA transporter

The striatum is the main input structure of the basal ganglia. Distinct striatal subfields are involved in voluntary movement generation and cognitive and emotional tasks, but little is known about the morphological and molecular differences of striatal subregions. The ventrolateral subfield of the striatum (VLS) is the orofacial projection field of the sensorimotor cortex and is involved in the development of orofacial dyskinesias, involuntary chewing-like movements that often accompany long-term neuroleptic treatment. The biological basis for this particular vulnerability of the VLS is not known. Potassium channels are known to be strategically localized within the striatum. In search of possible molecular correlates of the specific vulnerability of the VLS, we analyzed the expression of voltage-gated potassium channels in rodent and primate brains using qPCR, in situ hybridization, and immunocytochemical single and double staining. Here we describe a novel, giant, non-cholinergic interneuron within the VLS. This neuron coexpresses the vesicular GABA transporter, the calcium-binding protein parvalbumin (PV), and the Kv3.3 potassium channel subunit. This novel neuron is much larger than PV neurons in other striatal regions, displays characteristic electrophysiological properties, and, most importantly, is restricted to the VLS. Consequently, the giant striatal Kv3.3-expressing PV neuron may link compromised Kv3 channel function and VLS-based orofacial dyskinesias.

Management of Tardive Syndrome: Medications and Surgical Treatments

Tardive syndrome (TS) is an iatrogenic, often persistent movement disorder caused by drugs that block dopamine receptors. It has a broad phenotype including movement (orobuccolingual stereotypy, dystonia, tics, and others) and nonmotor features (akathisia and pain). TS has garnered increased attention of late because of the Food and Drug Administration approval of the first therapeutic agents developed specifically for this purpose. This paper will begin with a discussion on pathogenesis, clinical features, and epidemiology. However, the main focus will be treatment options currently available for TS including a suggested algorithm based on current evidence. Recently, there have been significant advances in TS therapy, particularly with the development of 2 new vesicular monoamine transporter type 2 inhibitors for TS and with new data on the efficacy of deep brain stimulation. The discussion will start with switching antipsychotics and the use of clozapine monotherapy which, despite the lack of higher-level evidence, should be considered for the treatment of psychosis and TS. Anti-dyskinetic drugs are separated into 3 tiers: 1) vesicular monoamine transporter type 2 inhibitors, which have level A evidence, are approved for use in TS and are recommended first-choice agents; 2) drugs with lower level of evidence for efficacy including clonazepam, Ginkgo biloba, and amantadine; and 3) drugs that have the potential to be beneficial, but currently have insufficient evidence including levetiracetam, piracetam, vitamin B6, melatonin, baclofen, propranolol, zolpidem, and zonisamide. Finally, the roles of botulinum toxin and surgical therapy will be examined. Current therapies, though improved, are symptomatic. Next steps should focus on the prevention and reversal of the pathogenic process.

Systematic review of interventions for treating or preventing antipsychotic-induced tardive dyskinesia

BACKGROUND

Antipsychotic medication can cause tardive dyskinesia (TD) - late-onset, involuntary, repetitive movements, often involving the face and tongue. TD occurs in > 20% of adults taking antipsychotic medication (first-generation antipsychotics for > 3 months), with this proportion increasing by 5% per year among those who continue to use these drugs. The incidence of TD among those taking newer antipsychotics is not different from the rate in people who have used older-generation drugs in moderate doses. Studies of TD have previously been found to be limited, with no treatment approach shown to be effective.

OBJECTIVES

To summarise the clinical effectiveness and safety of treatments for TD by updating past Cochrane reviews with new evidence and improved methods; to undertake public consultation to gauge the importance of the topic for people living with TD/the risk of TD; and to make available all data from relevant trials.

DATA SOURCES

All relevant randomised controlled trials (RCTs) and observational studies.

REVIEW METHODS

Cochrane review methods, network meta-analysis (NMA).

DESIGN

Systematic reviews, patient and public involvement consultation and NMA.

SETTING

Any setting, inpatient or outpatient.

PARTICIPANTS

For systematic reviews, adults with TD who have been taking a stable antipsychotic drug dose for > 3 months.

INTERVENTIONS

Any, with emphasis on those relevant to UK NHS practice.

MAIN OUTCOME MEASURES

Any measure of TD, global assessments and adverse effects/events.

RESULTS

We included 112 studies (nine Cochrane reviews). Overall, risk of bias showed little sign of improvement over two decades. Taking the outcome of 'TD symptoms improved to a clinically important extent', we identified two trials investigating reduction of antipsychotic dose [n = 17, risk ratio (RR) 0.42, 95% confidence interval (CI) 0.17 to 1.04; very low quality]. Switching was investigated twice in trials that could not be combined (switching to risperidone vs. antipsychotic withdrawal: one RCT, n = 42, RR 0.45, 95% CI 0.23 to 0.89; low quality; switching to quetiapine vs. haloperidol: one RCT, n = 45, RR 0.80, 95% CI 0.52 to 1.22; low quality). In addition to RCTs, six observational studies compared antipsychotic discontinuation with decreased or increased dosage, and there was no clear evidence that any of these strategies had a beneficial effect on TD symptoms (very low-quality evidence). We evaluated the addition to standard antipsychotic care of several treatments, but not anticholinergic treatments, for which we identified no trials. We found no clear effect of the addition of either benzodiazepines (two RCTs, n = 32, RR 1.12, 95% CI 0.6 to 2.09; very low quality) or vitamin E (six RCTs, n = 264, RR 0.95, 95% CI 0.89 to 1.01; low quality). Buspirone as an adjunctive treatment did have some effect in one small study (n = 42, RR 0.53, 95% CI 0.33 to 0.84; low quality), as did hypnosis and relaxation (one RCT, n = 15, RR 0.45, 95% CI 0.21 to 0.94; very low quality). We identified no studies focusing on TD in people with dementia. The NMA model found indirect estimates to be imprecise and failed to produce useful summaries on relative effects of interventions or interpretable results for decision-making. Consultation with people with/at risk of TD highlighted that management of TD remains a concern, and found that people are deeply disappointed at the length of time it has taken researchers to address the issue.

LIMITATIONS

Most studies remain small and poorly reported.

CONCLUSIONS

Clinicians, policy-makers and people with/at risk of TD are little better informed than they were decades ago. Underpowered trials of limited quality repeatedly fail to provide answers.

FUTURE WORK

TD reviews have data from current trials extracted, tabulated and traceable to source. The NMA highlights one context in which support for this technique is ill advised. All relevant trials, even if not primarily addressing the issue of TD, should report appropriate binary outcomes on groups of people with this problem. Randomised trials of treatments for people with established TD are indicated. These should be large (> 800 participants), necessitating accrual through accurate local/national registers, including an intervention with acceptable treatments and recording outcomes used in clinical practice.

STUDY REGISTRATION

This study is registered as PROSPERO CRD4201502045.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Gamma-aminobutyric acid agonists for antipsychotic-induced tardive dyskinesia

BACKGROUND

Chronic antipsychotic drug treatment may cause tardive dyskinesia (TD), a long-term movement disorder. Gamma-aminobutyric acid (GABA) agonist drugs, which have intense sedative properties and may exacerbate psychotic symptoms, have been used to treat TD.

OBJECTIVES

1. Primary objectiveThe primary objective was to determine whether using non-benzodiazepine GABA agonist drugs for at least six weeks was clinically effective for the treatment of antipsychotic-induced TD in people with schizophrenia, schizoaffective disorder or other chronic mental illnesses.2. Secondary objectivesThe secondary objectives were as follows.To examine whether any improvement occurred with short periods of intervention (less than six weeks) and, if this did occur, whether this effect was maintained at longer periods of follow-up.To examine whether there was a differential effect between the various compounds.To test the hypothesis that GABA agonist drugs are most effective for a younger age group (less than 40 years old).

SEARCH METHODS

We searched the Cochrane Schizophrenia Group Trials Register (last searched April 2017), inspected references of all identified studies for further trials, and, when necessary, contacted authors of trials for additional information.

SELECTION CRITERIA

We included randomised controlled trials of non-benzodiazepine GABA agonist drugs in people with antipsychotic-induced TD and schizophrenia or other chronic mental illness.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected and critically appraised studies, extracted and analysed data on an intention-to-treat basis. Where possible and appropriate we calculated risk ratios (RRs) and their 95% confidence intervals (CIs). For continuous data we calculated mean differences (MD). We assumed that people who left early had no improvement. We contacted investigators to obtain missing information. We assessed risk of bias for included studies and created a 'Summary of findings' table using GRADE.

MAIN RESULTS

We included 11 studies that randomised 343 people. Overall, the risk of bias in the included studies was unclear, mainly due to poor reporting; allocation concealment was not described, generation of the sequence was not explicit, participants and outcome assessors were not clearly blinded. For some studies we were unsure if data were complete, and data were often poorly or selectively reported.Data from six trials showed that there may be a clinically important improvement in TD symptoms after GABA agonist treatment compared with placebo at six to eight weeks follow-up (6 RCTs, n = 258, RR 0.83, CI 0.74 to 0.92; low-quality evidence). Data from five studies showed no difference between GABA agonist treatment and placebo for deterioration of TD symptoms (5 RCTs, n = 136, RR 1.90, CI 0.70 to 5.16; very low-quality evidence). Studies reporting adverse events found a significant effect favouring placebo compared with baclofen, sodium valproate or progabide for dizziness/confusion (3 RCTs, n = 62 RR 4.54, CI 1.14 to 18.11; very low-quality evidence) and sedation/drowsiness (4 RCTS, n = 144, RR 2.29, CI 1.08 to 4.86; very low-quality evidence). Studies reporting on akathisia (RR 1.05, CI 0.32 to 3.49, 2 RCTs, 80 participants), ataxia (RR 3.25, CI 0.36 to 29.73, 2 RCTs, 95 participants), nausea/vomiting (RR 2.61, CI 0.79 to 8.67, 2 RCTs, 64 participants), loss of muscle tone (RR 3.00, CI 0.15 to 59.89, 1 RCT, 10 participants), seizures (RR 3.00, CI 0.24 to 37.67, 1 RCT, 2 participants), hypotension (RR 3.04, CI 0.33 to 28.31, 2 RCTs, 119 participants) found no significant difference between GABA drug and placebo (very low-quality evidence). Evidence on mental state also showed no effect between treatment groups (6 RCTS, n = 121, RR 2.65, CI 0.71 to 9.86; very low-quality evidence) as did data for leaving the study early (around 10% in both groups, 6 RCTS, n = 218, RR 1.47, CI 0.69 to 3.15; very low-quality evidence). No study reported on social confidence, social inclusion, social networks, or personalised quality of life, a group of outcomes selected as being of particular importance to patients.

AUTHORS' CONCLUSIONS

We are uncertain about the evidence of the effects of baclofen, progabide, sodium valproate or tetrahydroisoxazolopyridinol (THIP) for people with antipsychotic-induced TD. Evidence is inconclusive and unconvincing. The quality of data available for main outcomes ranges from very low to low. Any possible benefits are likely to be outweighed by the adverse effects associated with their use.

Tardive Dyskinesia Associated with Atypical Antipsychotics: Prevalence, Mechanisms and Management Strategies

All antipsychotics, including the atypical antipsychotics (AAPs), may cause tardive dyskinesia (TD), a potentially irreversible movement disorder, the pathophysiology of which is currently unknown. The prevention and treatment of TD remain major challenges for clinicians. We conducted a PubMed search to review the prevalence and etiology of and management strategies for TD associated with AAPs. TD prevalence rates varied substantially between studies, with an estimated prevalence of around 20% in patients using AAPs. The risk of TD is lower with AAPs than with typical antipsychotics (TAPs) but remains a problem because AAPs are increasingly being prescribed. Important risk factors associated with TD include the duration of antipsychotic use, age, and ethnicity other than Caucasian. Theories about the etiology of TD include supersensitivity of the dopamine receptors and oxidative stress, but other neurotransmitters and factors are probably involved. Studies concerning the management of TD have considerable methodological limitations. Thus, recommendations for the management of TD are based on a few trials and clinical experience, and no general guidelines for the management of TD can be established. The best management strategy remains prevention. Caution is required when prescribing antipsychotics, and regular screening is needed for early detection of TD. Other strategies may include reducing the AAP dosage, switching to clozapine, or administering vesicular monoamine transporter (VMAT)-2 inhibitors. In severe cases, local injections of botulinum toxin or deep brain stimulation may be considered. More clinical trials in larger samples are needed to gather valid information on the effect of interventions targeting TD.

Clonazepam improves dopamine supersensitivity in a schizophrenia patient: a case report

Dopamine supersensitivity is an important consideration for assessing treatment-resistant schizophrenia. The emergence of dopamine supersensitivity might be related to upregulation of dopamine D2 receptor, which engenders tolerance to antipsychotics, rebound psychosis, and tardive dyskinesia (TD). A 24-year-old man with a history of treatment-resistant schizophrenia was hospitalized for treatment of bone fracture sustained during a suicide attempt. After the operation, his clinical symptoms implied malignant catatonia. The patient discontinued antipsychotics without rebound psychosis under clonazepam treatment. His psychotic symptoms were controlled further with 24 mg/day aripiprazole without relapse or worsening. Clonazepam might be an effective option for the management of dopamine supersensitivity psychosis (DSP).

New Models of Frontal-Subcortical Skeletomotor Circuit Pathology in Tardive Dyskinesia

Tardive dyskinesia (TD) is a hyperkinetic movement disorder that can occur as a side effect of treatment with antipsychotic medications. Because antipsychotics block the D2 family of dopamine receptors in the striatum, it has long been suspected this blockade contributes to the development of TD. Specifically, increased sensitivity of the dopamine receptors following chronic blockade has been thought to result in abnormal functioning of the frontal-subcortical (FSC) skeletomotor circuit and the symptoms of TD. However, this hypothesis remains unproven. In recent years, substantial research has focused on the basal ganglia and FSC circuits. This research has resulted in the development of the focused selection model of skeletomotor circuit function. This hypothesis provides a compelling model of neurocircuit abnormalities in TD. A greater understanding of the neuropathology of TD may lead to the development of better treatment and prevention strategies for this disorder. Furthermore, this information may contribute to a more complete understanding of normal skeletomotor circuit function and the role of circuit pathology in numerous neuropsychiatric conditions.

Tardive dyskinesia in patients treated with atypical antipsychotics: case series and brief review of etiologic and treatment considerations

Tardive dyskinesia (TD) is a disfiguring side-effect of antipsychotic medications that is potentially irreversible in affected patients. Newer atypical antipsychotics are felt by many to have a lower risk of TD. As a result, many clinicians may have developed a false sense of security when prescribing these medications. We report five cases of patients taking atypical antipsychotics who developed TD, review the risk of TD, its potential etiologic mechanisms, and treatment options available. The goal of this paper is to alert the reader to continue to be diligent in obtaining informed consent and monitoring for the onset of TD in patients taking atypical antipsychotics.

An investigation into the relationship between vigabatrin, movement disorders, and brain magnetic resonance imaging abnormalities in children with infantile spasms

AIM

We aimed to investigate the relationship between movement disorders, changes on brain magnetic resonance imaging (MRI), and vigabatrin therapy in children with infantile spasms.

METHOD

Retrospective review and brain MRI analysis of children enrolled in the International Collaborative Infantile Spasms Study (ICISS) who developed a movement disorder on vigabatrin therapy. Comparisons were made with controls within ICISS who had no movement disorder.

RESULTS

Ten of 124 infants had a movement disorder and in eight it had developed on vigabatrin therapy. Two had a movement disorder that resolved on dose-reduction of vigabatrin, one had improvement on withdrawing vigabatrin, two had resolution without any dose change, and in three it persisted despite vigabatrin withdrawal. The typical brain MRI changes associated with vigabatrin therapy were noted in two infants. Ten control infants were identified. Typical MRI changes noted with vigabatrin were noted in three controls.

INTERPRETATION

It is possible that in two out of eight cases, vigabatrin was associated with the development of a movement disorder. In six out of eight cases a causal relationship was less plausible. The majority of infants treated with vigabatrin did not develop a movement disorder. MRI changes associated with vigabatrin do not appear to be specifically related to the movement disorder.

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.

Gamma-aminobutyric acid agonists for neuroleptic-induced tardive dyskinesia

BACKGROUND

Chronic antipsychotic drug treatment may cause tardive dyskinesia (TD), a long-term movement disorder. Gamma-aminobutyric acid (GABA) agonist drugs, which have intense sedative properties and may exacerbate psychotic symptoms, have been used to treat TD.

OBJECTIVES

To determine the clinical effects of GABA agonist drugs (baclofen, gamma-vinyl-GABA, gamma-acetylenic-GABA, progabide, muscimol, sodium valproate and tetrahydroisoxazolopyridine (THIP) for people with schizophrenia or other chronic mental illnesses who also developed neuroleptic-induced tardive dyskinesia.

SEARCH STRATEGY

We updated the previous Cochrane review by searching the Cochrane Schizophrenia Group Register (June 2010).

SELECTION CRITERIA

We included reports if they were controlled trials dealing with people with neuroleptic-induced TD and schizophrenia or other chronic mental illness who had been randomly allocated to either non-benzodiazepine GABA agonist drugs with placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Working independently, we selected and critically appraised studies, extracted data and analysed on an intention-to-treat basis. Where possible and appropriate we calculated risk ratios (RR) and their 95% confidence intervals (CI) with the number needed to treat (NNT). For continuous data we calculated mean differences (MD).

MAIN RESULTS

We identified eight small poorly reported studies for inclusion. For the outcome of 'no clinically important improvement in tardive dyskinesia' GABA agonist drugs were not clearly better than placebo (n = 108, 3 RCTs, RR 0.83 CI 0.6 to 1.1). Deterioration in mental state was more likely to occur in people receiving GABA medication (n = 95, 4 RCTs, RR 2.47 CI 1.1 to 5.4), but this effect was influenced by the decision to assign a negative outcome to those who left early before the end of the study. A greater proportion of people allocated GABA medication may fail to complete the trial compared with those allocated placebo (20% versus 9%), but this difference was not statistically significant (n = 136, 5 RCTs, RR 1.99 CI 0.8 to 4.7). There is a suggestion of an increase in ataxia (loss of power of muscular coordination) for both baclofen and sodium valproate (n = 95, 2 RCTs, RR 3.26 CI 0.4 to 30.2), and in sedation (n = 113, 3 RCTs, RR 2.12 CI 0.8 to 5.4) compared with placebo, but this was not significant. Withdrawal of tetrahydroisoxazolopyridine (THIP) may cause seizures.

AUTHORS' CONCLUSIONS

Evidence of the effects of baclofen, progabide, sodium valproate, or THIP for people with antipsychotic-induced TD is inconclusive and unconvincing. Any possible benefits are likely to be outweighed by the adverse effects associated with their use.

Effect of Chronic Nicotine Treatment and Withdrawal on Rat Striatal D1 and D2 Dopamine Receptors

The effects on rat striatal dopamine receptors after chronic nicotine administration (3 and 12 mg kg−1 day−1), and after withdrawal from chronic nicotine (12 mg kg−1 day−1), were studied. After 21 days of continuous minipump infusion, the control (saline) and nicotine-treated rats were killed. The nicotine-withdrawal rats were killed on day 28, 7 days after pump removal. Radioligand studies were performed to determine D1 ([3H]SCH23390) and D2 ([3H]spiperone) striatal dopamine receptor affinity (Kd) and maximum binding (Bmax). Dopamine inhibition of antagonist binding at 3 concentrations and the effect of 0·3 Mm GTP on binding affinity were examined. No statistically significant differences between control and nicotine treatment or withdrawal groups were noted in either D1 or D2 receptor Kd or Bmax. Although nicotine has been shown to affect nigrostriatal dopamine release, chronic treatment does not appear to alter overall striatal dopaminergic receptor binding parameters.

Genetic underpinnings of tardive dyskinesia: passing the baton to pharmacogenetics

Manifestation of tardive dyskinesia (TD) among schizophrenia subjects on long-term antipsychotic treatment with typical drugs has been a clinical concern. Despite its association with extrapyramidal symptoms, typical drugs are still routinely prescribed globally though marginally superior atypical drugs have long been available. The genetic component in the etiology of TD is well documented. Search for these determinants has led to a few consensus associations of CYP2D6 *10, CYP1A2*1F, DRD2 Taq1A (rs1800497), DRD3 Ser9Gly (rs6280) and MnSOD Ala9Val (rs4880) variants with TD. However, translation of these observations into the clinic has not been achieved so far. This review discusses the salient features of TD etiopathology, current status of TD genetics, interactions between genetic and nongenetic factors, some major drawbacks, challenges and expected focus in TD research over the next decade, with emphasis on pharmacogenetics.

Modulatory effect of neurosteroids in haloperidol-induced vacuous chewing movements and related behaviors

RATIONALE

Tardive dyskinesia is a syndrome of abnormal and involuntary movements which occurs as a complication of long-term neuroleptic therapy especially classical neuroleptics such as haloperidol and chlorpromazine. Dysfunction of GABA receptor mediated inhibition, and increased glutamatergic neurotransmission has been implicated in the development of orofacial dyskinesia in rats and tardive dyskinesia in humans. Neurosteroids modulate both GABAergic as well as glutamatergic neurotransmission in various brain areas.

OBJECTIVE

The objective of the present study was to elucidate the role of various neurosteroids in neuroleptic-induced vacuous chewing movements and related behaviors in rats by using behavioral, biochemical, and neurochemical parameters.

MATERIALS AND METHODS

Animals chronically treated with haloperidol (1 mg/kg i.p.) for a period of 21 days exhibited marked increase in vacuous chewing movements, tongue protrusions, and facial jerkings as compared to vehicle-treated controls. It also resulted in increased superoxide anion levels and lipid peroxidation, whereas decreased levels of endogenous antioxidant enzymes (catalase and superoxide dismutase) in rat brain striatum homogenates. Neurochemical studies revealed that chronic administration of haloperidol resulted in significant decrease in the levels of dopamine, serotonin, and norepinephrine in rat brain striatum homogenates, whereas urine biogenic amines metabolite levels were increased. In a series of experiments, rats co-administered with allopregnanolone (0.5, 1, and 2 mg/kg i.p.) and progesterone (5, 10, and 20 mg/kg i.p.), both positive GABA-modulating [negative N-methyl-D-aspartate (NMDA)-modulating] neurosteroids prevented, whereas pregnenolone (0.5, 1, and 2 mg/kg i.p.) and dihydroxyepiandrosterone sulfate (0.5, 1, and 2 mg/kg i.p.) both negative GABA-modulating (positive NMDA-modulating) neurosteroids aggravated all the behavioral, biochemical, and neurochemical parameters.

CONCLUSIONS

These results suggest that neurosteroids may play a significant role in the pathophysiology of vacuous chewing movements and related behaviors by virtue of their action on either the GABA or NMDA modulation. Furthermore, neurosteroids showing selectivity for positive GABA modulation and/or negative NMDA modulation may be particularly efficacious as novel therapeutic agents for the treatment of tardive dyskinesia and deserve further evaluation.

Schizophrenia endophenotypes as treatment targets

Schizophrenia is a complex disorder that encompasses several clinical symptom domains and functional impairments. Existing treatments are meager, effective only against positive symptoms without benefiting negative symptoms and functional impairments. The drug discovery process has focused mostly on targeting D2 dopamine receptors. This followed the serendipitous discovery of the antipsychotic effects of chlorpromazine in the 1950s and, more recently, clozapine. There is a need to identify novel mechanisms in order to discover novel drugs that are effective against each of the symptom clusters and functional impairments associated with the illness. Neurophysiological studies in schizophrenia over the past 3 decades have identified several brain deficits that are stable, using valid animal models that are related to the etiology of the disorder. Many of these deficits are distinct and heritable; these are called endophenotypes. Many have well-characterized neurobiology and may therefore provide molecular targets for drug development. In addition, these endophenotypes help reduce the heterogeneity by identifying homogeneous subgroups of patients with similar pathophysiology, symptoms and functional deficits. Clinical trials of drugs, whose development is based on an endophenotype, will have enhanced statistical power when the trial is carried out in an appropriate cohort of subjects using outcome measures related to the corresponding endophenotype. Furthermore, genes that are associated with these endophenotypes are beginning to be identified. These findings will identify novel molecular targets for drug development with treatment implications for clinical symptom complex and functional deficits marked by the endophenotype. As endophenotypes are present during childhood and adolescence, novel drugs that are developed on the basis of this subgroup could have implications for preventive strategies in schizophrenia.

World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for biological treatment of schizophrenia, part 2: long-term treatment of schizophrenia

These guidelines for the biological treatment of schizophrenia were developed by an international Task Force of the World Federation of Societies of Biological Psychiatry (WFSBP). The goal during the development of these guidelines was to review systematically all available evidence pertaining to the treatment of schizophrenia, and to reach a consensus on a series of practice recommendations that are clinically and scientifically meaningful based on the available evidence. These guidelines are intended for use by all physicians seeing and treating people with schizophrenia. The data used for developing these guidelines have been extracted primarily from various national treatment guidelines and panels for schizophrenia, as well as from meta-analyses, reviews and randomised clinical trials on the efficacy of pharmacological and other biological treatment interventions identified by a search of the MEDLINE database and Cochrane Library. The identified literature was evaluated with respect to the strength of evidence for its efficacy and then categorised into four levels of evidence (A-D). This second part of the guidelines covers the long-term treatment as well as the management of relevant side effects. These guidelines are primarily concerned with the biological treatment (including antipsychotic medication, other pharmacological treatment options, electroconvulsive therapy, adjunctive and novel therapeutic strategies) of adults suffering from schizophrenia.

Effects of baclofen on reserpine-induced vacuous chewing movements in mice

We have described that GABA mimetic drugs present the ability to inhibit the expression of reserpine-induced oral movements. In this respect, oral movements is associated with important neuropathologies. This study investigates the effects of an acute or a repeated treatment of different doses of the GABA(B) agonist baclofen, as well as withdrawal from these treatments, on the development and/or expression of reserpine-induced vacuous chewing movements (VCM). Male mice received two injections of vehicle or of 1mg/kg reserpine separated by 48 h. In the first experiment, 24h later, animals were acutely treated with vehicle or baclofen (1, 2 or 4 mg/kg). In the second experiment, animals were treated with vehicle or baclofen (1 or 4 mg/kg) for four consecutive days receiving a concomitant injection of 1mg/kg reserpine (or vehicle) on Days 2 and 4. Twenty-four hours later, animals received vehicle or baclofen. Thirty minutes after the last injection, they were observed for quantification of VCM and open-field general activity. The acute administration of all the doses of baclofen abolished the manifestation of reserpine-induced VCM. Repeated treatment with 1mg/kg baclofen induced tolerance to the ability of an acute injection of this dose to reduce VCM. Treatment with baclofen (4 mg/kg) did not modify spontaneous VCM. Acute administration of the highest dose induced a decrease in general motor activity and a potentiation of the reserpine-induced decrease in general activity. These results reinforce the involvement of GABAergic hypofunction in the expression of oral movements and suggest that a repeated treatment with baclofen induces compensatory changes in GABAergic transmission that can attenuate its acute property to decrease VCM.

GABA(A) receptor subtypes as targets for neuropsychiatric drug development

The main inhibitory neurotransmitter system in the brain, the gamma-aminobutyric acid (GABA) system, is the target for many clinically used drugs to treat, for example, anxiety disorders and epilepsy and to induce sedation and anesthesia. These drugs facilitate the function of pentameric A-type GABA (GABA(A)) receptors that are extremely widespread in the brain and composed from the repertoire of 19 subunit variants. Modern genetic studies have found associations of various subunit gene polymorphisms with neuropsychiatric disorders, including alcoholism, schizophrenia, anxiety, and bipolar affective disorder, but these studies are still at their early phase because they still have failed to lead to validated drug development targets. Recent neurobiological studies on new animal models and receptor subunit mutations have revealed novel aspects of the GABA(A) receptors, which might allow selective targeting of the drug action in receptor subtype-selective fashion, either on the synaptic or extrasynaptic receptor populations. More precisely, the greatest advances have occurred in the clarification of the molecular and behavioral mechanisms of action of the GABA(A) receptor agonists already in the clinical use, such as benzodiazepines and anesthetics, rather than in the introduction of novel compounds to clinical practice. It is likely that these new developments will help to overcome the present problems of the chronic treatment with nonselective GABA(A) agonists, that is, the development of tolerance and dependence, and to focus the drug action on the neurobiologically and neuropathologically relevant substrates.

Effects of gabaergic drugs on reserpine-induced oral dyskinesia

Recently we have described the antidyskinetic property of the GABA mimetic drugs valproic acid and topiramate on reserpine-induced oral dyskinesia. In this respect, oral dyskinesia has been associated with important neuropathologies. The present study investigates the effects of different doses of the GABA(A) agonist tetrahydroisoxazolopyridine (THIP), of the GABA(B) agonist baclofen as well as of the GABA(A) modulator diazepam on the manifestation of reserpine-induced orofacial dyskinesia. Male Wistar rats received two injections of vehicle or of 1mg/kg reserpine separated by 48 h. Twenty-four hours later, animals were acutely treated with vehicle or THIP (2, 4 or 8 mg/kg), baclofen (1, 2 or 4 mg/kg) or diazepam (1, 2 or 4 mg/kg) and were observed for quantification of oral dyskinesia and open-field general activity. In order to verify the effects of these drugs per se on spontaneous oral movements, male Wistar rats were acutely treated with vehicle, 8 mg/kg THIP, 4 mg/kg baclofen or 4 mg/kg diazepam and observed for quantification of oral dyskinesia. The two highest doses of THIP or of baclofen abolished the manifestation of reserpine-induced oral dyskinesia while the lowest dose of baclofen attenuated it. Diazepam did not modify reserpine-induced oral dyskinesia at any dose tested. The highest doses of these drugs did not modify spontaneous oral movements. Reserpine-induced decrease in open-field general activity was not modified by any of the doses of THIP and diazepam or by the two lowest doses of baclofen. The highest dose of baclofen potentiated the increase in the duration of immobility induced by reserpine. These results reinforce the involvement of GABAergic hypofunction in the expression of oral dyskinesias, and support the potential therapeutic use of THIP and baclofen in the treatment of oral dyskinesias.

GABAergic dysfunction in schizophrenia and mood disorders as reflected by decreased levels of glutamic acid decarboxylase 65 and 67 kDa and Reelin proteins in cerebellum

BACKGROUND

Glutamic acid decarboxylase (GAD) is the rate limiting enzyme responsible for conversion of glutamate to gamma-aminobutyric acid (GABA) regulating levels of glutamate and GABA in the mammalian brain. Reelin is an extracellular matrix protein that helps in normal lamination of the embryonic brain and subserves synaptic plasticity in adult brain. Both GAD and Reelin are colocalized to the same GABAergic interneurons in several brain sites. We hypothesized that levels of GAD and Reelin would be altered in cerebellum of subjects with schizophrenia and mood disorders differentially vs. controls.

METHODS

We employed SDS-PAGE and Western blotting to measure levels of GAD isomers 65 and 67 kDa and Reelin isoforms 410-, 330- and 180-kDa proteins as well as beta-actin in cerebellum of subjects with schizophrenia, bipolar disorder and major depression vs. controls (N = 15 per group).

RESULTS

GAD 65- and 67-kDa levels were decreased significantly in bipolar, depressed and schizophrenic subjects (p < 0.05) vs. controls. Reelin 410- and 180-kDa proteins decreased significantly (p < 0.05) in bipolar subjects vs. controls. Reelin 180 kDa was decreased significantly (p < 0.05) in schizophrenics vs. controls. beta-Actin levels did not vary significantly between groups. There were no significant effects of confounding variables on levels of various proteins.

CONCLUSION

This study demonstrates for the first time significant deficits in GABAergic markers Reelin and GAD 65 and 67 proteins in bipolar subjects and global deficits in the latter proteins in schizophrenia and mood disorders, accounting for the reported alterations in CSF/plasma levels of glutamate and GABA in these disorders.

Effects of topiramate on oral dyskinesia induced by reserpine

Recently, we have described the antidyskinetic property of the GABA mimetic drug valproic acid on reserpine-induced oral dyskinesia, an animal model that has been related to tardive as well as acute dyskinesias, which are associated with important neuropathologies. The present study investigates the effects of different doses of the GABA mimetic anticonvulsant topiramate on the manifestation of reserpine-induced orofacial dyskinesia. Female EPM-M1 mice received two injections of control solution or of 0.5 mg/kg reserpine separated by 48 h. Twenty-four hours after the second reserpine or control solution injection, animals were acutely treated with control solution or topiramate (1, 3, 10 or 30 mg/kg) and were observed for quantification of oral dyskinesia or general activity in an open-field. In order to verify the effects of topiramate per se on oral dyskinesia or general activity, female EPM-M1 mice were acutely treated with control solution or 1, 3, 10 or 30 mg/kg topiramate and observed for quantification of oral dyskinesia and general activity. The highest dose of topiramate completely abolished the manifestation of reserpine-induced oral dyskinesia whereas the doses of 3 and 10 mg/kg significantly attenuated it. None of the doses of the anticonvulsant modified spontaneous locomotion frequency or oral movements, whereas spontaneous rearing frequency was decreased by 3, 10 and 30 mg/kg topiramate. The highest dose of topiramate did not modify general activity in reserpine-treated mice. These results support the potential therapeutic use of topiramate in the treatment of oral dyskinesias.

Gamma-aminobutyric acid agonists for neuroleptic-induced tardive dyskinesia

BACKGROUND

Chronic antipsychotic drug treatment may cause tardive dyskinesia (TD), a long-term movement disorder. Gamma-aminobutyric acid (GABA) agonist drugs, which have intense sedative properties and may exacerbate psychotic symptoms, have been used to treat TD.

OBJECTIVES

To determine the effects of GABA agonist drugs (baclofen, gamma-vinyl-GABA, gamma-acetylenic-GABA, progabide, muscimol, sodium valproate and tetrahydroisoxazolopyridine (THIP)) for people with antipsychotic-induced tardive dyskinesia (TD) and schizophrenia or other chronic mental illnesses.

SEARCH STRATEGY

We updated the previous Cochrane review by searching the Cochrane Schizophrenia Group Register (September 2003). We searched references for further trial citations and, where possible, contacted authors.

SELECTION CRITERIA

Randomised controlled trials comparing use of non-benzodiazepine GABA agonist drugs with placebo or no intervention, involving people with schizophrenia or other chronic mental illnesses with signs of antipsychotic-induced TD.

DATA COLLECTION AND ANALYSIS

Working independently, we selected and critically appraised studies, extracted data and analysed on an intention-to-treat basis. Where possible and appropriate we calculated risk ratios (RR) and their 95% confidence intervals (CI) with the number needed to treat (NNT). For continuous data Weighted Mean Differences (WMD) were calculated.

MAIN RESULTS

We identified eight small poorly reported studies for inclusion. For the outcome of 'no clinically important improvement in tardive dyskinesia' GABA agonist drugs were not clearly better than placebo (n = 108, RR 0.83 CI 0.6 to 1.1). Deterioration in mental state was more likely to occur in people receiving GABA medication (n = 95, RR 2.47 CI 1.1 to 5.4), but this effect was influenced by the decision to assign a negative outcome to those who dropped out before the end of the study. A greater proportion of people allocated GABA medication may fail to complete the trial compared with those allocated placebo (20% versus 9%), but this difference was not statistically significant (n = 136, RR 1.99 CI 0.8 to 4.7). There is a suggestion of an increase in ataxia (loss of power of muscular coordination) for both baclofen and sodium valproate (n = 95, RR 3.26 CI 0.4 to 30.2), and in sedation (n = 113, RR 2.12 CI 0.8 to 5.4) compared with placebo, but this was not significant. Withdrawal of tetrahydroisoxazolopyridine (THIP) may cause seizures.

REVIEWERS' CONCLUSIONS

Evidence of the effects of baclofen, progabide, sodium valproate, or THIP for people with antipsychotic-induced TD is inconclusive and unconvincing. Any possible benefits are likely to be outweighed by the adverse effects associated with their use.

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.

Effects of valproic acid on an animal model of tardive dyskinesia

GABAergic hypofunction in the basal ganglia is stated as an important mechanism underlying the pathophysiology of tardive dyskinesia. The present study investigates the effects of the GABA-mimetic drug valproic acid (VA) on the manifestation of reserpine-induced orofacial movements, an animal model of tardive dyskinesia. Male Wistar rats received two injections of control solution or of 1 mg/kg reserpine separated by 48 h. Twenty-four hours later, animals were acutely treated with 50, 100, or 200 mg/kg VA or control solution and were observed for quantification of orofacial movements and of open-field general activity. The highest dose of VA inhibited the manifestation of reserpine-induced orofacial movements but none of the VA doses modified reserpine-induced decrease in open-field general activity. These results support the potential of VA as an effective pharmacological tool in the treatment of tardive dyskinesia.

Changes of GABA receptors and dopamine turnover in the postmortem brains of parkinsonians with levodopa-induced motor complications

Brain samples from 14 Parkinson's disease patients, 10 of whom developed motor complications (dyskinesias and/or wearing-off) on dopaminomimetic therapy, and 11 controls were analyzed. Striatal 3beta-(4-(125)I-iodophenyl)tropane-2beta-carboxylic acid isopropyl ester ([(125)I]RTI-121) -specific binding to dopamine transporter and concentration of dopamine were markedly decreased, but no association between level of denervation and development of motor complications was observed. The homovanillic acid/dopamine ratio of concentrations was higher in putamen of patients with wearing-off compared to those without. Striatal (35)S-labeled t-butylbicyclophosphorothionate ([(35)S]TBPS) and [(3)H]flunitrazepam binding to GABA(A) receptors were unchanged in patients with Parkinson's disease, whereas [(125)I]CGP 64213 -specific binding to GABA(B) receptors was decreased in the putamen and external segment of the globus pallidus of parkinsonian patients compared with controls. [(3)H]Flunitrazepam binding was increased in the putamen of patients with wearing-off compared to those without. [(35)S]TBPS-specific binding was increased in the ventral internal globus pallidus of dyskinetic subjects. These data suggest altered dopamine metabolism and increased GABA(A) receptors in the putamen related to the pathophysiology of wearing-off. The present results also suggest that an up-regulation of GABA(A) receptors in the internal globus pallidus is linked to the pathogenesis of levodopa-induced dyskinesias.

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

The effects of three chronically administered antipsychotic drugs on selected neurochemical markers of dopaminergic and GABAergic transmission were compared within the cerebral regions making up the basal ganglia-thalamocortical parallel processing neuronal pathways. All three drugs reduce psychosis in humans, whereas only haloperidol, but not olanzapine or sertindole, induce purposeless oral chewing movements (CMs) in rats or cause high rates of parkinsonism or tardive dyskinesia in humans. Male Sprague Dawley rats were treated with haloperidol, sertindole, or olanzapine delivered in drinking water for 6 months at doses which produce drug plasma levels in rat in the human therapeutic range. Results show the expected dopamine D2 receptor upregulation in striatum predominantly with haloperidol, although mild D2 upregulation was apparent in striatum after olanzapine. GAD67 mRNA was increased in striatum and decreased in globus pallidus by haloperidol and sertindole, but not by olanzapine. In the substantia nigra pars reticulata (SNR), both olanzapine and sertindole failed to induce GABA(A) receptor upregulation or D1 receptor downregulation, but haloperidol did both, confirming a previous report. In thalamus, all three drugs increased GAD expression in the reticular nucleus, whereas only haloperidol decreased GABA(A) binding in the mediodorsal nucleus, actions consistent with a reduction in nigrothalamic, GABA-mediated neural transmission. These results are consistent with the idea that the two new antipsychotics tested have mild and regionally restricted actions within the basal ganglia nuclei and a common action on increasing GAD expression in the reticular nucleus of the thalamus (RtN). Haloperidol, in contrast, has a broad and potent action in basal ganglia, causing changes in SNR and in the mediodorsal nucleus, while also altering GAD mRNA in RtN, potentially reflective of its dyskinetic and antipsychotic actions.

The current status of tardive dyskinesia

OBJECTIVE

This paper aims to provide an overview of the current knowledge on neuroleptic-induced tardive dyskinesia (TD) in relation to its clinical features, risk factors, pathophysiology and management.

METHOD

The published literature was selectively reviewed and assessed.

RESULTS

Tardive diskinesia is a common neurological side-effect of neuroleptic medication, the cumulative incidence of which increases with increasing duration of treatment. Its clinical manifestations are diverse and subsyndromes have been described. Many risk factors for TD are now recognised, but increasing age remains pre-eminent as a risk factor. The pathophysiology of TD is not completely understood. Of the neurotransmitter hypotheses, the dopamine receptor supersensitivity hypothesis and the gamma-aminobutyric acid insufficiency hypothesis are the main contenders. There is increasing recognition that TD may in fact be caused by neuroleptic-induced neuronal toxicity through free radical and excitotoxic mechanisms. The occurrence of spontaneous dyskinesias in schizophrenic patients and even healthy subjects suggests that neuroleptics act on a substratum of vulnerability to dyskinesia. As no effective treatment for TD is available, the primary emphasis is on prevention. Many drugs can be tried to reduce symptoms in established cases. The increasing use of atypical neuroleptics has raised the possibility of a lower incidence of TD in the future.

CONCLUSIONS

After four decades of clinical recognition, the pathophysiology of TD is still not understood and no effective treatment is available. Its prevention with the optimal usage of currently available drugs and regular monitoring of patients on long-term neuroleptic treatment remain the best strategies to reduce its impact.

Gamma-aminobutyric acid agonists for neuroleptic-induced tardive dyskinesia

BACKGROUND

Chronic antipsychotic drug treatment may cause tardive dyskinesia (TD), a long-term movement disorder. The gamma-aminobutyric acid (GABA) agonist drugs have been trialed as a treatment for TD, but these drugs have intense sedative properties and can possibly exacerbate psychotic symptoms.

OBJECTIVES

To determine the effects of GABA agonist drugs (baclofen, gamma-vinyl-GABA, gamma-acetylenic-GABA, progabide, muscimol, sodium valproate and tetrahydroisoxazolopyridine (THIP)) in people with neuroleptic-induced tardive dyskinesia (TD) and schizophrenia or other chronic mental illnesses.

SEARCH STRATEGY

Electronic searches of Biological Abstracts (1982-1998), The Cochrane Library CENTRAL (1998), Cochrane Schizophrenia Group's Register of Trials (1998), EMBASE (1980-1998), LILACS (1982-1996), MEDLINE (1966-1998), PsycLIT (1974-1998), and SCISEARCH were undertaken. References of all identified studies were searched for further trial citations. First authors of each included trial were contacted.

SELECTION CRITERIA

The inclusion criteria for all relevant randomised studies were that they should focus on people with schizophrenia or other chronic mental illnesses, with neuroleptic-induced TD and compare the use of GABA agonist drugs to placebo or no intervention.

DATA COLLECTION AND ANALYSIS

The reviewers extracted the data independently and the odds ratio (OR) and its 95% confidence interval (CI) or the weighted mean difference with 95% CI were estimated. The reviewers assumed that people who dropped out had no improvement.

MAIN RESULTS

Eight studies were able to be included. Results were equivocal, showing only a tendency for clinical improvement for those using GABA agonist drugs but, when analysis of any improvement (rather than clinical improvement) was performed, a significant reduction was noted in the GABA group (OR 0.36 CI 0.15-0.85). This suggests that for every 10 people treated with GABA drugs one person would benefit with a reduction in TD symptoms. People using the interventions had more confusion (OR 7.4 CI 1.3-40.9) and sedation (OR 3.0 CI 1.2-7.6). The numbers of people needed to treat to cause one extra person to experience these side effects were three and six, respectively. Tendency for more deterioration of the TD symptoms (OR 1.72 CI 0. 54-5.5), deterioration of the mental state (OR 3.07 CI 0.78-12.05), and to drop out before the end of the trial (OR 2.05 CI 0.8-5.21) were also observed in those using GABA agonists.

REVIEWER'S CONCLUSIONS

No clear statement about the efficacy of GABA agonist drugs could be provided. From the combined data, GABA agonist drugs tend to be associated with some degree of improvement in TD symptoms, but also with side effects such as confusion and sedation and a deterioration of the person's mental state.

The treatment of tardive dyskinesia--a systematic review and meta-analysis

This systematic review aimed to collate randomized controlled trials (RCTs) of various interventions used to treat tardive dyskinesia (TD) and, where appropriate, to combine the data for meta-analysis. Clinical trials were identified by electronic searches, handsearches and contact with principal investigators. Data were extracted independently by two reviewers, for outcomes related to improvement, deterioration, side-effects and drop out rates. Data were pooled using the Mantel-Haenzel Odds Ratio (fixed effect model). For treatments that had significant effects, the number needed to treat (NNT) was calculated. From 296 controlled clinical trials, data were extracted from 47 trials. For most interventions, we could identify no RCT-derived evidence of efficacy. A meta-analysis showed that baclofen, deanol and diazepam were no more effective than a placebo. Single RCTs demonstrated a lack of evidence of any effect for bromocriptine, ceruletide, clonidine, estrogen, gamma linolenic acid, hydergine, lecithin, lithium, progabide, seligiline and tetrahydroisoxazolopyridinol. The meta-analysis found that five interventions were effective: L-dopa, oxypertine, sodium valproate, tiapride and vitamin E; neuroleptic reduction was marginally significant. Data from single RCTs revealed that insulin, alpha methyl dopa and reserpine were more effective than a placebo. There was a significantly increased risk of adverse events associated with baclofen, deanol, L-dopa, oxypertine and reserpine. Meta-analysis of the impact of placebo (n=485) showed that 37.3% of participants showed an improvement. Interpretation of this systematic review requires caution as the individual trials identified tended to have small sample sizes. For many compounds, data from only one trial were available, and where meta-analyses were possible, these were based on a small number of trials. Despite these concerns, the review facilitated the interpretation of the large and diverse range of treatments used for TD. Clinical recommendations for the treatment of TD are made, based on the availability of RCT-derived evidence, the strength of that evidence and the presence of adverse effects.

The Maryland Psychiatric Research Center scale and the characterization of involuntary movements

The Maryland Psychiatric Research Center involuntary movement scale (MPRC scale) has been used in the evaluation of 1107 patients referred for drug-induced movement disorders. The scale has increased discrimination of body area and severity compared to other scales. Validity was examined using principal component analyses, pharmacologic response studies and associations with AIMS, global judgement and motor diagnosis. Reliability was examined using Cronbach's alpha, intraclass correlation coefficient (ICC) between raters and test-retest measurements. The prevalence of dyskinetic and parkinsonian signs at several levels of severity are reported. Total dyskinesia was strongly correlated with AIMS score, r = 0.97. Inter-rater reliability was 0.81-0.90 for total dyskinesia score. Receiver Operating Characteristic (ROC) analysis shows a total dyskinesia score of 4 or above to predict tardive dyskinesia, consistent with RDC-TD criteria. Hand dyskinesia showed a high prevalence comparable to that of oral dyskinesias. The MPRC scale is a valid, sensitive and reliable instrument for the rating of neuroleptic-induced dyskinetic and parkinsonian syndromes and may offer advantages over other scales in neurophysiologic research and brain imaging with its ease of use, uniform structure and greater discrimination of anatomic place and severity in the rating of involuntary movements.

Cerebrospinal fluid gamma-aminobutyric acid in patients with panic disorder

Cerebrospinal fluid (CSF) gamma-aminobutyric acid (GABA) levels were measured in 11 patients with panic disorder (PD) prior to and following 7 months of treatment with alprazolam or imipramine and in six neurological control patients. Although a clear treatment response was observed in patients with PD, neither alprazolam nor imipramine significantly changed CSF GABA during the treatment period. A negative correlation was demonstrated between baseline CSF GABA and posttreatment overt psychopathology. Low pretreatment level of CSF GABA correlated significantly with poor therapeutic outcome, judged by the amount of anxiety and depression as well as by the frequency of panic attacks at the end of follow-up.

Effect of muscimol on haloperidol-induced alteration of neurotensin gene expression in the striatum and nucleus accumbens in the rat

Acute neuroleptic administration increases the expression of neurotensin/neuromedin (NT/N) gene in rat dorsolateral striatum and shell sector of the nucleus accumbens. The purpose of this study was to examine modulation of neuroleptic induction of NT/N and the proto-oncogene c-fos expression by the GABAA agonist muscimol. Adult male Sprague-Dawley rats were treated with saline, haloperidol (1 mg/kg); muscimol (3.2 mg/kg); or haloperidol (1 mg/kg) plus muscimol (3.2 mg/kg). Animals were sacrificed 1 h after drug administration. Expression of NT/N and c-fos mRNA was examined by in situ hybridization using 35S-antisense probes. Muscimol alone had no measurable effect on basal levels of NT/N or c-fos mRNA in either the dorsolateral striatum or the nucleus accumbens. However, co-administration of muscimol with haloperidol reduced haloperidol-induced increases in NT/N as well as c-fos mRNA in the dorsolateral striatum. In contrast, NT/N mRNA expression in accumbal shell induced by haloperidol was not modulated by co-administration of muscimol. These data suggest that GABAA receptors may be involved in regulation of NT/N gene expression in the DLSt, but not in the nucleus accumbens.

Chronic haloperidol, but not clozapine, produces altered oral movements and increased extracellular glutamate in rats

Rats administered chronic haloperidol or clozapine in their drinking water for 6 months were monitored for changes in oral movements using a computerized video analysis system. Haloperidol-treated animals exhibited late onset increases in small amplitude oral movements and an increase in the percentage of oral movements in the 1-2 Hz range, accompanied by a decrease in oral movements in the higher frequency range (> 6 Hz) as determined by fast fourier analysis. In contrast, clozapine-treated rats showed a decrease in medium-sized amplitude oral movements, but did not demonstrate significant changes in the distribution of oral movements across frequencies. Extracellular concentrations of gamma-aminobutyric acid (GABA) and glutamate in the ventrolateral striatum were then assessed by intracranial microdialysis during oral drug administration and 3 days after drug withdrawal. Extracellular GABA and glutamate levels were not significantly different between groups during drug administration. However, 3 days after drug withdrawal, there was a significant increase in glutamate in the haloperidol-treated rats. No changes were noted for glutamate levels in clozapine-treated rats or for GABA levels in either group following withdrawal. These results confirm the atypical profile of clozapine in an animal model of tardive dyskinesia and suggest that alterations in striatal glutamatergic function follow typical, but not atypical, antipsychotic drug administration.

Tiagabine inhibits haloperidol-induced oral dyskinesias in rats

Chronic administration of haloperidol to male Sprague Dawley rats for 6 months at a dosage of 1.5 mg/kg/day produces oral dyskinesias in a significant percent of the treated group. This has been used as an animal model of tardive dyskinesia in several laboratories, because the rat movements display characteristics reminiscent of the human dyskinetic condition. Previously, we have reported a reduction in these haloperidol-induced oral dyskinesias with the coadministration of a direct acting GABA agonist progabide. Here, we have tested an indirect acting GABA agonist, tiagabine, coadministered with haloperidol, for its effect on the oral dyskinesias. At a dosage of 75 mg/kg/day tiagabine significantly inhibited the onset of vacuous chewing movements (VCMs), decreasing the average movement severity from 11.2 +/- 2.0 to 4.4 +/- 1.4, compared with a placebo rate of 1.3 +/- 0.5 (VCMs/5 min). These data support the proposition that an effective, potent GABAmimetic coadministered with haloperidol, will block the onset of rat oral dyskinesias. This conclusion has important implications for the treatment and prevention of tardive dyskinesia in humans.

Treatment of schizophrenia: a clinical and preclinical evaluation of neuroleptic drugs

Forty years after the first clinical report on the effectiveness of chlorpromazine in psychiatric patients, neuroleptic drugs are still the most widely used drugs in the treatment of schizophrenia. Indeed, there are no other drugs which have proven to be as effective in the treatment of this severe psychiatric disorder. Yet, there are still many unresolved problems relating to neuroleptic drugs. The present review gives a comprehensive overview of our knowledge (and our lack of knowledge) with respect to the clinical and preclinical effects of neuroleptic drugs and tries to integrate this knowledge in order to identify the neuronal mechanisms underlying the therapeutic and side effects of neuroleptic drugs.

GABA agonist-induced changes in motor, oculomotor, and attention measures correlate in schizophrenics with tardive dyskinesia

Saccadic distractibility, Stroop color-word scores, and serial dyskinesia assessments were obtained on 10 schizophrenic patients with tardive dyskinesia during a pharmacologic challenge with placebo or 7 mg muscimol, a potent, direct-acting GABA agonist. Although no significant difference in the measures was evident between conditions, a significant correlation was found between GABA agonist-induced changes in saccadic distractibility and dyskinesia scores where no correlation existed between these measures on placebo. Improvement in saccadic distractibility was also correlated with reduction in attention performance, as measured by Stroop. These effects are not due to sedation. The correlation between dyskinesia and saccadic distractibility is consistent with a model of parallel motor and oculomotor cortico-striatal-thalamic circuits in humans. This work supports the hypothesis that a dysfunction in GABA-mediated neurotransmission may be the basis for tardive dyskinesia.

Chronic neuroleptic administration decreases extracellular GABA in the nucleus accumbens but not in the caudate-putamen of rats

The extracellular levels of gamma-aminobutyric acid (GABA) in the caudate-putamen and the nucleus accumbens of rats following administration of haloperidol decanoate, fluphenazine decanoate, or vehicle for 8 months were assessed using intracranial microdialysis. Basal levels of extracellular GABA were significantly decreased in the nucleus accumbens of both neuroleptic-treated groups while levels of GABA in the caudate-putamen were not significantly different between groups. These results provide evidence for selective chronic neuroleptic-induced effects on in vivo GABA function in different terminal regions containing dopamine receptors.

GABA and behavior: the role of receptor subtypes

The discovery of different GABA receptor subtypes has stimulated research relating this neurotransmitter to a variety of behavioral functions and clinical disorders. The development of new and specific GABAergic compounds has made it possible to try to identify the specific functions of these receptors. The purpose of the present review is to evaluate the data regarding the functions of the GABA receptor subtypes in different behaviors such as motor function, reproduction, learning and memory, and aggressive-defensive behaviors. A description of GABAergic functions (stress, peripheral effects, thermoregulation) that might directly or indirectly affect behavior is also included. The possible involvement of GABA in different neurological and psychiatric disorders is also discussed. Although much research has been done trying to identify the possible role of GABA in different behaviors, the role of receptor subtypes has only recently attracted attention, and only preliminary data are available at present. It is therefore evident that still much work has to be done before a clear picture of the behavioral significance of these receptor subtypes can be obtained. Nevertheless, existing data are sufficient to justify the prediction that GABAergic agents, in the near future, will be much used in the field of behavioral pharmacology. It is hoped that the present review will contribute to this. Some specific suggestions concerning the most efficient way to pursue future research are also made.

Chronic neuroleptic treatment: D2 dopamine receptor supersensitivity and striatal glutamatergic transmission

We studied the in vitro electrical activity of rat neostriatal neurons following chronic neuroleptic treatment. In haloperidol-treated rats, unlike naive animals, activation of neostriatal D2 dopamine receptors induced a potent presynaptic inhibition of glutamate-mediated excitatory synaptic potentials. Haloperidol treatment did not affect the intrinsic membrane properties of the neostriatal neurons. Pre- and postsynaptic physiological responses to direct and indirect gamma-aminobutyric acid (GABA)-ergic and cholinergic agonists were not affected by chronic haloperidol treatment. These findings suggest that movement disorders induced by chronic neuroleptic treatment may result, at least in part, from a hypersensitivity of presynaptic D2 dopamine receptors regulating the release of glutamate.

Co-administration of progabide inhibits haloperidol-induced oral dyskinesias in rats

Vacuous chewing movements in rats may be an animal analogue of the human motor disorder, tardive dyskinesia. The movements are phenomenologically and pharmacologically similar to tardive dyskinesia. The pathophysiology of these involuntary oral movements, and perhaps of tardive dyskinesia, are likely to include both dopamine receptor changes, and alterations in GABA (gamma-aminobutyric acid) system function. In an attempt to test the involvement of GABA system dysfunction in these movements, we treated rats chronically with water alone, haloperidol alone, the GABA agonist progabide alone, and haloperidol plus progabide. Sprague-Dawley rats received haloperidol (1.5 mg/kg per day) in their drinking water and progabide (100 mg/kg per day) in their food for 12 months. After 12 months of treatment, haloperidol had induced vacuous chewing movements when administered alone, but the prevalence of the movements was decreased by 40% with the coadministration of progabide. Moreover, the haloperidol-progabide-treated animals did not merely demonstrate movement suppression but actual inhibition of movement onset, as determined by an additional progabide-withdrawal experiment. These data would suggest that progabide and perhaps other GABAmimetic compounds can prevent the development of tardive dyskinesia in man.

Tardive dyskinesia and chronic pain

Psychotropic drugs are frequently used to treat chronic pain. Tardive dyskinesia is a serious complication of such therapy, but is not mentioned in the pain literature. Two cases are reported and the implications discussed.

Pharmacological characterization of tardive akathisia

A patient with tardive neuroleptic-induced akathisia was investigated with multiple pharmacological challenges. It was noted that the patient responded positively to benztropine, bromocriptine, and propranolol, and negatively to physostigmine, and showed little or no response to discontinuation of neuroleptics and challenges with metoclopramide, metoprolol, atenolol, and clonidine. The implications of this pharmacological characterization for the understanding of the pathophysiology of tardive akathisia in relation to acute akathisia and tardive dyskinesia are discussed.

The psychopharmacology of GABA synapses: update 1989

Recent advances in the psychopharmacology of GABA synapses are reviewed. The usefulness of GABA mimetics in tardive dyskinesia and epilepsy has been confirmed, as has a dysfunction of GABA synapses in the etiopathology of these conditions. The antidepressant profile of GABA agonists in animal models for depression has been extended. The role of GABA receptors in the mechanism of action of antidepressants has been further delineated, with a parallelism occurring between the behavioral and biochemical response to antidepressant drug treatment in different animal models of depression.