Neuroleptic medications inhibit complex I of the electron transport chain

A mitochondrial DNA sequence variant associated with schizophrenia and oxidative stress

We have previously reported a changed mitochondrial (mt) gene expression in brain from patients with schizophrenia [Schizophr. Res. 14 (1995) 203]; now, we describe the distribution in the mtDNA from lymphocytes of a heteroplasmic sequence variation that was originally found in the mtDNA from the postmortem brain of a patient with schizophrenia. The variant is m.12027T>C and results in the change from isoleucine to threonine at position 423 of the ND4 subunit of NADH-ubiquinone reductase. Using a PCR-RFLP method, we have determined the heteroplasmy as the ratio of variant to total (variant ratio) at m.12027 in 184 controls and 181 patients with schizophrenia as well as 24 postmortem brain samples. The distribution of variants is bimodal having peaks at variant ratios of 0.262 and 0.732. The variant-rich fraction is very significantly associated with schizophrenia in males (47%), while there is only 18% in control males. There are significantly more variant-rich control females (36%) than control males (18%), suggesting that the female population is less sensitive to the presence of a variant in terms of liability to schizophrenia. In variant-rich samples from postmortem brain originating from both sexes, there is an increased superoxide production, suggesting that the variation contributes to oxidative stress. Antioxidant glycosides, such as quercetin rutoside, quench the superoxide production without (in contrast to neuroleptic drugs) interfering with the electron transfer activity of the reductase.

Differential effects of typical and atypical neuroleptics on mitochondrial functionin vitro

A series of typical (chlorpromazine, haloperidol and thioridazine) and atypical (risperidone, quetiapine, clozapine and olanzapine) antipsychotics were tested for effects on integrated bioenergetic functions of isolated rat liver mitochondria. Polarographic measurement of oxygen consumption in freshly isolated mitochondria showed that electron transfer activity at respiratory complex I is inhibited by chlorpromazine, haloperidol, risperidone, and quetiapine, but not by clozapine, olanzapine, or thioridazine. Chlorpromazine and thioridazine act as modest uncouplers of oxidative phosphorylation. The typical neuroleptics inhibited NADH-coenzyme Q reductase in freeze-thawed mitochondria, which is a direct measure of complex I enzyme activity. The inhibition of NADH-coenzyme Q reductase activity by the atypicals risperidone and quetiapine was 2-4 fold less than that for the typical neuroleptics. Clozapine and olanzapine had only slight effects on NADH-coenzyme Q reductase activity, even at 200 microM. The relative potencies of these neuroleptic drugs as inhibitors of mitochondrial bioenergetic function is similar to their relative potencies as risk factors in the reported incidence of extrapyramidal symptoms, including tardive dyskinesia (TD). This suggests that compromised bioenergetic function may be involved in the cellular pathology underlying TD.

Acute cardiac failure in neuroleptic malignant syndrome

We present a case of rapid onset acute cardiac failure developing as part of neuroleptic malignant syndrome in a 35-year-old woman following treatment with thioridazine and lithium. Post mortem histology of cardiac and skeletal muscle showed similar changes of focal cellular necrosis and vacuolation suggesting a common disease process.

State-dependent alterations in mitochondrial complex I activity in platelets: a potential peripheral marker for schizophrenia

Schizophrenia, the most severe psychiatric disorder, is characterized by heterogeneity of clinical signs, often categorized into positive and negative symptoms. Among a wide array of competing biological mechanisms, altered cerebral energy metabolism and mitochondrial dysfunction have been suggested to play an important role in the pathophysiology of schizophrenia. In this study we investigated mitochondrial complex I in platelets of 113 schizophrenic patients divided into three groups (acute psychotic episode, chronic active state and residual schizophrenia) and 37 control subjects. Complex I was analysed at the level of enzymatic activity, mRNA and protein levels by enzyme kinetics, RT-PCR and Western blot analyses, respectively. Complex I activity in platelets of schizophrenic patients altered with disease state presenting high specificity and sensitivity. Thus, increased activity was associated with psychotic symptomology, while its decrease was observed in patients with residual schizophrenia. The relationship between the clinical state and complex I activity in schizophrenia was further supported by its positive correlation with the severity of patients' positive symptoms assessed by clinical ratings. In addition, similar alterations were observed at the levels of mRNA and protein of the 24- and 51-kDa iron-sulfur flavoprotein subunits of the complex. Taken together these results point to the potential of platelet complex I to turn into a reliable novel marker for schizophrenia. At present, definitive diagnosis depends only on descriptive behavioral and symptomatic information, therefore a peripheral measurable specific marker will contribute to diagnosis and monitoring of the disease.

Cytotoxicity of conventional and atypical antipsychotic drugs in relation to glucose metabolism

The goal of these studies was to analyze the cytotoxicity of both the conventional and atypical antipsychotic drugs in relation to their effects on glucose metabolism. The drugs were evaluated for their effects on the viability of PC12 cells, which are an established model of neuronal cells in culture. In general, the conventional drugs, such as chlorpromazine, fluphenazine and pimozide, were more toxic than the atypical drugs, including clozapine, quetiapine and risperidone. Olanzapine was unique in that it stimulated cell proliferation in this system. There was a good correlation between the cytotoxicity of a drug and its ability to block glucose transport, although there were some exceptions to this trend. Conventional antipsychotics also affected the expression of glucose transporter proteins in whole cell extracts and at the cell surface. Overall, the data support the notion that many of the antipsychotic drugs associated with the development of movement disorders in patients are cytotoxic for cultured cells.

Oxidative mechanisms and tardive dyskinesia

Tardive dyskinesia has been and continues to be a significant problem associated with long-term antipsychotic use, but its pathophysiology remains unclear. In the last 10 years, preclinical studies of the administration of antipsychotics to animals, as well as clinical studies of oxidative processes in patients given antipsychotic medications, with and without tardive dyskinesia, have continued to support the possibility that neurotoxic free radical production may be an important consequence of antipsychotic treatment, and that such production may relate to the development of dyskinetic phenomena. In line with this hypothesis, evidence has accumulated for the efficacy of antioxidants, primarily vitamin E (alpha-tocopherol), in the treatment and prevention of tardive dyskinesia. Early studies suggested a modest effect of vitamin E treatment on existing tardive dyskinesia, but later studies did not demonstrate a significant effect. Because evidence has continued to accumulate for increased oxidative damage from antipsychotic medications, but less so for the effectiveness of vitamin E, especially in cases of long-standing tardive dyskinesia, alternative antioxidant approaches to the condition may be warranted. These approaches may include the use of antioxidants as a preventive measure for tardive dyskinesia or the use of other antioxidants or neuroprotective drugs, such as melatonin, for established tardive dyskinesia.

Possible mechanism of action in melatonin attenuation of haloperidol-induced orofacial dyskinesia

Tardive dyskinesia (TD) is a late complication of prolonged neuroleptic treatment characterized by involuntary movements of the oral region. In spite of high incidence and much research, the pathophysiology of this devastating movement disorder remains elusive. Chronic treatment with neuroleptics leads to the development of abnormal oral movements in rats, referred to as vacuous chewing movements (VCMs). VCMs in rats are widely accepted as an animal model of TD. Rats chronically treated with haloperidol (1.5 mg/kg ip) significantly developed VCMs and tongue protrusions. Melatonin dose-dependently (1, 2, and 5 mg/kg) reversed the haloperidol-induced VCM and tongue protrusions frequencies. Biochemical analysis reveals that chronic haloperidol treatment significantly induced lipid peroxidation and decreased the forebrain glutathione (GSH) levels in the rats. Chronic haloperidol-treated rats also showed decreased levels of antioxidant defense enzymes, superoxide dismutase (SOD), and catalase. Coadministration of melatonin (1, 2, and 5 mg/kg) along with haloperidol significantly reduced the lipid peroxidation and restored the decreased GSH levels by chronic haloperidol treatment, and significantly reversed the haloperidol-induced decrease in forebrain SOD and catalase levels in rats. However, a lower dose of melatonin (1 mg/kg) failed to reverse chronic haloperidol-induced decreases in forebrain GSH, SOD, and catalase levels. In conclusion, melatonin could be screened as a potential drug candidate for the prevention or treatment of neuroleptic-induced orofacial dyskinesia.

Oral dyskinesias and histopathological alterations in substantia nigra after long-term haloperidol treatment of old rats

The pathophysiologic basis of tardive dyskinesia remains unclear, but several lines of evidence suggest that persistent neuronal changes in the basal ganglia produced by oxidative stress or glutamate toxicity may play a role, especially in the elderly. In the present study we examined whether histopathological alterations in substantia nigra are related to oral dyskinesia in a rodent model of tardive dyskinesia. Haloperidol decanoate (38 mg/kg/4 weeks) was administered to young (8 weeks) and old (38 weeks) rats for a total period of 28 weeks, and the development of vacuous chewing movements (VCM) was observed. Rats with high and low levels of VCM and saline-treated controls were analyzed for histopathological alterations. Reduced nerve cell number and atrophic neurons were prominent features in the substantia nigra of old rats with high levels of VCM. Some alterations were also present in the substantia nigra of the old rats with low levels of VCM and young rats with high VCM levels, but these were significantly less affected than the high VCM rats. These results show that the development of haloperidol-induced oral dyskinesias in old rats is associated with histopathological alterations in the substantia nigra. This suggests that nigral degeneration induced by neuroleptics may contribute to the development of persistent VCM in rats and possibly irreversible tardive dyskinesia in humans.

Mitochondrial dysfunction in schizophrenia: a possible linkage to dopamine

Mitochondria are not only the principal source of high energy intermediates, but play an important role in intracellular calcium buffering, are main producers of reactive oxygen species, and are the source of pro- and antiapoptotic key factors. Moreover, the mitochondria are of a ubiquitous nature and the respiratory chain has a dual genetic basis, i.e. the mitochondrial and the nuclear DNAs. Thus mitochondrial impairment could provide an explanation for the tremendous heterogeneity of clinical and pathological manifestations in schizophrenia. This article reviews several independent lines of evidence that suggest an involvement of mitochondrial dysfunction in schizophrenia. Among them are altered cerebral energy metabolism, mitochondrial hypoplasia, dysfunction of the oxidative phosphorylation system and altered mitochondrial related gene expression. In addition, the interaction between dopamine, a predominant etiological factor in schizophrenia, and mitochondrial respiration is considered as a possible mechanism underlying the hyper- and hypo-activity cycling in schizophrenia. Understanding the role of mitochondria in schizophrenia may encourage novel treatment approaches, the identification of candidate genes and new insights into the pathophysiology and etiology of the disorder.

The genetic basis of Parkinson's disease

Although the mechanisms underlying neurodegeneration in Parkinson's disease are not fully understood, considerable evidence suggests that genetic factors can influence susceptibility to the disease. In this article, we critically review this evidence and examine studies estimating patterns of inheritance. In a few families, Parkinson's disease is clearly inherited in a Mendelian fashion, and in some of these the disease causing genes have already been identified. Possible pathogenic mechanisms by which these genes cause Parkinson's disease are discussed. Further candidate genes and systematic efforts to identify genes influencing susceptibility to the disease in general are also summarised. The identification of such susceptibility genes will eventually enable us to more accurately classify this complex disease.

Carvedilol attenuates neuroleptic-induced orofacial dyskinesia: possible antioxidant mechanisms

1. Tardive dyskinesia (TD), a syndrome of potentially irreversible, involuntary hyperkinetic disorder occurring in 20 - 40% of the patient population undergoing chronic neuroleptic treatment is a major limitation of neuroleptic therapy. 2. Oxidative stress and products of lipid peroxidation are implicated in the pathophysiology of various neurological disorders including tardive dyskinesia. 3. Chronic treatment with neuroleptics leads to the development of abnormal oral movements in rats known as vacuous chewing movements (VCMs). Vacuous chewing movements in rats are widely accepted as an animal model of tardive dyskinesia. 4. All the antipsychotics were administered i.p. once daily for 21 days, whereas carvedilol (also i.p.) was administered twice daily. Rats chronically treated with haloperidol (1.0 mg kg(-1)) or chlorpromazine (5 mg kg(-1)) but not clozapine (2 mg kg(-1)) significantly developed vacuous chewing movements and tongue protrusions. Carvedilol dose dependently (0.5 - 2 mg kg(-1)) reduced the haloperidol or chlorpromazine-induced vacuous chewing movements and tongue protrusions. 5. Biochemical analysis revealed that chronic haloperidol or chlorpromazine but not clozapine treatment significantly induced lipid peroxidation and decreased the glutathione (GSH) levels in the forebrains of rats. Chronic haloperidol or chlorpromazine but not clozapine treated rats showed decreased forebrain levels of antioxidant defence enzymes, superoxide dismutase (SOD) and catalase. 6. Co-administration of carvedilol (0.5-2 mg kg(-1)) significantly reduced the lipid peroxidation and restored the decreased glutathione levels by chronic haloperidol or chlorpromazine treatment. Co-administration of carvedilol (1-2 mg kg(-1)) significantly reversed the haloperidol or chlorpromazine-induced decrease in forebrain SOD and catalase levels in rats. However, lower dose of carvedilol (0.5 mg kg(-1)) failed to reverse chronic haloperidol or chlorpromazine-induced decrease in forebrain SOD and catalase levels. 7. The major findings of the present study suggest that oxidative stress might play a significant role in neuroleptic-induced orofacial dyskinesia. In conclusion, carvedilol could be a useful drug for the treatment of neuroleptic-induced orofacial dyskinesia.

Antipsychotic drugs and neuroplasticity: insights into the treatment and neurobiology of schizophrenia

This paper reviews the evidence that antipsychotic drugs induce neuroplasticity. We outline how the synaptic changes induced by the antipsychotic drug haloperidol may help our understanding of the mechanism of action of antipsychotic drugs in general, and how they may help to elucidate the neurobiology of schizophrenia. Studies have provided compelling evidence that haloperidol induces anatomical and molecular changes in the striatum. Anatomical changes have been documented at the level of regional brain volume, synapse morphology, and synapse number. At the molecular level, haloperidol has been shown to cause phosphorylation of proteins and to induce gene expression. The molecular responses to conventional antipsychotic drugs are predominantly observed in the striatum and nucleus accumbens, whereas atypical antipsychotic drugs have a subtler and more widespread impact. We conclude that the ability of antipsychotic drugs to induce anatomical and molecular changes in the brain may be relevant for their antipsychotic properties. The delayed therapeutic action of antipsychotic drugs, together with their promotion of neuroplasticity suggests that modification of synaptic connections by antipsychotic drugs is important for their mode of action. The concept of schizophrenia as a disorder of synaptic organization will benefit from a better understanding of the synaptic changes induced by antipsychotic drugs.

Effects of chronic haloperidol and clozapine treatments on frontal and caudate neurochemistry in schizophrenia

N-Acetyl-aspartate (NAA), a marker of neuronal integrity, has been found to be reduced in frontal regions in schizophrenia. However, the impact of antipsychotic drug type on NAA has not been carefully evaluated. We studied outpatients with schizophrenia/schizoaffective disorders chronically treated with haloperidol or clozapine and normal controls with single-voxel 1H-MRS of the caudate nuclei and the left frontal lobe. Concentrations of NAA, choline containing compounds (Cho) and creatine plus phosphocreatine (Cre) were determined and corrected for the proportion of cerebrospinal fluid (CSF) in each voxel. The haloperidol-treated group had significantly lower CSF-uncorrected and CSF-corrected left frontal NAA than the normal controls, with the clozapine group having intermediate concentrations. The haloperidol-treated group had significantly lower CSF-uncorrected caudate NAA than the normal controls, but the three groups did not differ after correcting for CSF fraction. Performance times in the Grooved Pegboard, a measure of motor dexterity and proxy for parkinsonism, were correlated with CSF-uncorrected and CSF-corrected left frontal NAA. Demographic and illness-related variables were not related to NAA. Exposure to haloperidol-like drugs may in part account for the frontal NAA reductions previously reported in schizophrenia. Adjustment for proportion of voxel CSF should be considered in 1H-MRS studies.

Protein thiol oxidation by haloperidol results in inhibition of mitochondrial complex I in brain regions: comparison with atypical antipsychotics

Usage of 'typical' but not 'atypical' antipsychotic drugs is associated with severe side effects involving extrapyramidal tract (EPT). Single dose of haloperidol caused selective inhibition of complex I in frontal cortex, striatum and midbrain (41 and 26%, respectively) which was abolished by pretreatment of mice with thiol antioxidants, alpha-lipoic acid and glutathione isopropyl ester, and reversed, in vitro, by disulfide reductant, dithiothreitol. Prolonged administration of haloperidol to mice resulted in complex I loss in frontal cortex, hippocampus, striatum and midbrain, while chronic dosing with clozapine affected only hippocampus and frontal cortex. Risperidone caused complex I loss in frontal cortex, hippocampus and striatum but not in midbrain from which extrapyramidal tract emanates. Inhibition of the electron transport chain component, complex I by haloperidol is mediated through oxidation of essential thiol groups to disulfides, in vivo. Further, loss of complex I in extrapyramidal brain regions by anti-psychotics correlated with their known propensity to generate side-effects involving extra-pyramidal tract.

Metabolic defects caused by treatment with the tetrahydropyridine analog of haloperidol (HPTP), in baboons

Mounting evidence suggests that compromised cellular energy production is a major contributor to idiopathic and drug-induced degenerative processes. Our interest in neurotoxins have prompted us to examine in the baboon the effects of HPTP, the tetrahydropyridine dehydration product of haloperidol, on urinary chemical markers that reflect defects in mitochondrial respiration. Urinary dicarboxylic acid and conjugate profiles, similar to those seen in humans with inborn errors of mitochondrial metabolism and toxin-induced Jamaican vomiting sickness (JVS) were observed in the treated baboons. We interpret these results as evidence that HPTP and/or HPTP metabolites inhibit mitochondrial respiration in the baboon and speculate that analogous effects may occur in haloperidol-treated individuals.

Evidence for a mitochondrial oxidative phosphorylation defect in brains from patients with schizophrenia

In-vivo imaging studies and post-mortem studies have demonstrated an impairment of energy metabolism in brains of patients with schizophrenia. Decreased oxidative metabolism has been consistently documented in the frontal lobes. However, the biochemical basis of these changes is unclear. The changes could be caused by reduced requirement of the cells for metabolic energy or an abnormality in energy generation. Neurons generate energy through the respiratory chain in the mitochondria. The respiratory chain consists of five enzyme complexes (I-V). The purpose of the present study was to assess mitochondrial function and test the hypothesis of an underlying oxidative phosphorylation defect in schizophrenia. We analysed spectrophotometrically post-mortem brain specimens of frontal cortex, temporal cortex, basal ganglia, and cerebellum of 12 patients who met the DSM-IV criteria for schizophrenia and of 13 healthy controls for the specific activities of respiratory chain enzymes in the mitochondria. The major finding was that the activity of complex IV was significantly reduced in the frontal cortex (40.9+/-6.7 vs. 87.3+/-12, P=0.003) and in the temporal cortex (39.5+/-6.8 vs. 78+/-10.8, P=0.006) of schizophrenics. In addition, the activity of complexes I+III was significantly reduced in the temporal cortex (2.2+/-0.6 vs. 4.4+/-0.5, P=0.01) and basal ganglia (1.6+/-0.5 vs. 3.4+/-0.3, P=0.015) in schizophrenia. All other enzyme activities showed no differences to healthy controls. The results confirm a defect of oxidative phosphorylation in brains from patients with schizophrenia, which may contribute to impaired energy generation.

Mitochondrial dysfunction in bipolar disorder

Mitochondrial dysfunction is implicated in bipolar disorder based on the following lines of evidence: 1) Abnormal brain energy metabolism measured by 31P-magnetic resonance spectroscopy, that is, decreased intracellular pH, decreased phosphocreatine (PCr), and enhanced response of PCr to photic stimulation. 2) Possible role of maternal inheritance in the transmission of bipolar disorder. 3) Increased levels of the 4977-bp deletion in mitochondrial DNA (mtDNA) in autopsied brains. 4) Comorbidity of affective disorders in certain types of mitochondrial disorders, such as autosomal inherited chronic progressive external ophthalmoplegia and mitochondrial diabetes mellitus with the 3243 mutation. Based on these findings, we searched for mtDNA mutations/ polymorphisms associated with bipolar disorder and found that 5178C and 10398A polymorphisms in mtDNA were risk factors for bipolar disorder. The 5178C genotype was associated with lower brain intracellular pH. mtDNA variations may play a part in the pathophysiology of bipolar disorder through alteration of intracellular calcium signaling systems. The mitochondrial dysfunction hypothesis, which comprehensively accounts for the pathophysiology of bipolar disorder, is proposed.

Neurotoxicity associated with neuroleptic-induced oral dyskinesias in rats. Implications for tardive dyskinesia?

Tardive dyskinesia is a serious motor side effect of long-term treatment with neuroleptics, with an unknown pathophysiologic basis. Brain damage and aging are prominent risk-factors, and together with the persistent character of the disorder, it is likely that long-lasting neuronal changes are involved in the pathogenesis. It has been hypothesized that striatal neurodegeneration caused by excitotoxic mechanisms and oxidative stress may play an important role in the development of the disorder, and the scope of the present work is to review the evidence supporting this hypothesis. The rat model of tardive dyskinesia has been used extensively in the field, and the usefulness of this model will be discussed. Neuroleptics are able to induce oxidative stress in vitro and increase striatal glutamatergic activity in rats, which may lead to toxic effects in the striatum. Drugs that block excitotoxicity inhibit the development of persistent oral dyskinesia in the rat model, and impaired energy metabolism leads to increased frequency of oral dyskinesia. There are also signs of altered striatal histology in rats with high frequency of oral dyskinesia. Furthermore, markers of increased oxidative stress and glutamatergic neurotransmission have been found in the cerebrospinal fluid of patients with tardive dyskinesia. In conclusion, several lines of evidence implicate neurotoxic events in the development of neuroleptic induced tardive dyskinesia.

Muscle changes in the neuroleptic malignant syndrome

AIMS

To characterise the skeletal muscle changes in the neuroleptic malignant syndrome (NMS).

METHODS

Detailed light and ultrastructural examination was carried out on skeletal muscle from three cases of NMS, two associated with recreational drugs (3,4-methlenedioxymethylamphetamine (MDMA, Ecstasy) and lysergic acid diethylamide (LSD)) and one with antipsychotic drugs (fluoxetine (Prozac) and remoxipride hydrochloride monohydrate (Roxiam)).

RESULTS

The muscles were grossly swollen and oedematous in all cases, in one with such severe local involvement that the diagnosis of sarcoma was considered. On microscopy, there was conspicuous oedema. In some fascicles less than 10% of fibres were affected whereas in others more than 50% were pale and enlarged. There was a spectrum of changes: tiny to large vacuoles replaced most of the sarcoplasm and were associated with necrosis. A striking feature in some fibres was the presence of contraction bands separating segments of oedematous myofibrils. Severe endomysial oedema was also detectable. There was a scanty mononuclear infiltrate but no evidence of regeneration.

CONCLUSIONS

The muscle changes associated with NMS are characteristic and may be helpful in differential diagnosis.

Mitochondrial ultrastructure and density in a primate model of persistent tardive dyskinesia

The use of neuroleptic drugs to treat schizophrenia is almost invariably associated with extrapyramidal movement disorders. One of these disorders, tardive dyskinesia (TD), can persist long after neuroleptic withdrawal suggesting that permanent neurological damage is produced. However, there appears to be no convincing pathology of TD and its pathogenesis remains unknown. Findings that neuroleptics interfere with normal mitochondrial function and produce mitochondrial ultrastructural changes in the basal ganglia of patients and animals suggest that mitochondrial dysfunction plays a role in TD. We have established a model for persistent TD in baboons that appears to involve compromised mitochondrial function. In this study, we evaluated two animals treated for 41 weeks with a derivative of haloperidol and two treated with vehicle only. Treatment was then withdrawn and the animals observed for a further 17-18 weeks. Treated animals developed abnormal orofacial signs that were consistent with TD. These symptoms persisted during the drug-free period. The animals were euthanased, the brains perfused-fixed then post-fixed in 4% paraformaldehyde and the caudate and putamen prepared for electron microscopy. Regardless of whether mitochondria were located in neural soma, excitatory terminals, glia or in non-somal neuropil there was no consistent difference either in size or number between treated and control animals. Thus, even if mitochondria in striatal neurons undergo ultrastructural alterations during neuroleptic therapy, these changes do not persist after drug withdrawal.

Reduced number of striatal neurons expressing preprosomatostatin mRNA in rats with oral dyskinesias after long-term haloperidol administration

Neuroleptic-induced oral dyskinesia in rats, a putative analogue to human tardive dyskinesia, may be due to degeneration within the striatum. Using unbiased stereological methods, a decreased number of striatal neurons expressing preprosomatostatin mRNA was observed only in rats that developed pronounced oral dyskinesias after 30 weeks of haloperidol administration. The amount of preprosomatostatin mRNA in each striatal neuron, measured in terms of optical densities of individual neurons, was not affected by haloperidol. A tendency toward a reduction in the number of NADPH-diaphorase positive neurons was observed in rats receiving haloperidol. These results indicate that the mechanism by which neuroleptics induce oral dyskinesias in rats, and perhaps tardive dyskinesia in humans, involves a functional disruption and possibly damage of a subpopulation of interneurons in the striatum.

Coenzyme Q10 does not prevent oral dyskinesias induced by long-term haloperidol treatment of rats

Tardive dyskinesia (TD) is a debilitating side effect of long-term treatment with neuroleptics with an unclear pathophysiologic basis. It has been proposed that TD may be a result of neuroleptic-induced oxidative stress. To investigate this hypothesis, we studied if neuroleptic-induced oral dyskinesias in rats, a putative analogue to human TD, could be prevented by the antioxidant coenzyme Q10 (CoQ10). Rats received 16 weeks of treatment with haloperidol decanoate (HAL) IM alone or together with orally administered CoQ10, and the behavior was recorded during and after treatment. HAL significantly increased the level of oral dyskinesias, and the increase persisted for 12 weeks after drug withdrawal. Cotreatment with CoQ10 did not attenuate the development of HAL-induced oral dyskinesia. Despite adequate absorption of orally administered CoQ10, shown by the increased serum levels of CoQ10, no increase of either CoQ10 or coenzyme Q9 was detected in the brain. These results suggest that cotreatment with CoQ10 does not inhibit the development of HAL-induced oral dyskinesias in rats, and that further studies seem to be needed in order to clarify the pharmacokinetics of CoQ10 in rats.

Inhibition of mitochondrial oxidative phosphorylation induces hyper-expression of glutamic acid decarboxylase in pancreatic islet cells

It has been hypothesised that mitochondrial dysfunction in pancreatic beta cells could produce hyper-expression of glutamic acid decarboxylase (GAD), a major autoantigen in insulin-dependent diabetes mellitus (IDDM) (Degli Esposti, M. and Mackay, I.R. Diabetologia 40: 352-356, 1997). Here we report that specific inhibition of mitochondrial respiration enhances the expression of GAD in both foetal mouse pancreatic tissue and hamster HIT-T15 cells. Inhibitors of NADH-ubiquinone oxidoreductase (complex I) seem to be particularly effective in increasing the expression of GAD in both foetal mouse pancreas and HIT-T15 hamster beta cells, especially in the presence of nutrients such as arginine and glucose. These results represent the first evidence that GAD expression is enhanced under conditions that are toxic to pancreatic beta cells, and establish a link between mitochondrial dysfunction and expression of IDDM autoantigens.

Nitric oxide, superoxide, and hydrogen peroxide production in brain mitochondria after haloperidol treatment

Inhibition of mitochondrial respiration and free radical induction have been suggested to be involved in haloperidol neurotoxicity. In this study, mice were injected i.p. with haloperidol, according to two different treatments: (a) a single injection (1 mg/kg), sacrificed 1 h after the injection (single-dose model); and (b) two injections (1 mg/kg each), sacrificed 24 h after the first dose (double-dose model). Determinations of oxygen consumption and hydrogen peroxide (H2O2) production rate were carried out in isolated brain mitochondria. Nitric oxide (NO) and superoxide (O2-) production rates were measured in submitochondrial particles (SMP). Single-dose haloperidol treatment produced a 33% inhibition in malate-glutamate-dependent respiration, while no significant changes were found after double-dose treatment. NO production was inhibited by 39 and 54% in SMP from haloperidol-treated mice (single- and double-dose treatments, respectively) (control value: 1.6 +/- 0.2 nmol/min mg protein). NO steady-state concentration was estimated at about 16.5 nM and was decreased by 40% by haloperidol treatment. Increases of 105 and 54% were found in succinate-supported O2- and H2O2 production rates, respectively, after haloperidol single-dose treatment. Haloperidol treatment generated a 248% increase in SMP O2- production rate when measured in the presence of NADH plus rotenone. Our results suggest that haloperidol neurotoxicity would be mediated by a decreased mitochondrial NO production, a decreased intramitochondrial NO steady-state concentration, and by an inhibition of mitochondrial electron transfer with enhancement of O2- and H2O2 production. This inhibition does not seem to be caused by increased NO or ONOO- formation.

Genetics, drugs and environmental factors in Parkinson's disease. A case-control study

A case-control study of Parkinson's disease (PD) was conducted in the city of Rio de Janeiro based on the assumption that neurotoxins with secondary parkinsonian action may be related to the development of Parkinson's disease. Ninety-two subjects with PD and 110 controls were queried through a questionnaire in order to investigate possible risk factors for the disease. The following factors were studied: herbicides/pesticides, exposure to chemicals, ingestion of drugs with secondary PD effects, rural life, water well source, family history, cranial trauma and cigarette smoking. Study of mentioned factors was achieved through univariate, stratified and multivariate analyses. Univariate and multivariate analyses demonstrated that PD was positively associated with family history (OR = 14.5; CI = 2.98-91.38), with the use of drugs with secondary PD action (OR = 11.01; CI = 3.41-39.41) and with exposure to chemical agents (OR = 5.87; CI = 1.48-27.23). PD was found to be inversely associated with cigarette smoking (OR = 0.39; IC = 0.16-0.95). Stratified analysis only confirmed family history and drug use, besides demonstrating that cigarette consumption could be a protection factor, when aforementioned factors were involved. This study might be a warning as to the cares that need to be taken regarding drug use and occupational exposure to chemical agents, as both types of substances present secondary PD action.

Differential diagnosis of Parkinson's disease

The differential diagnosis of PD includes other neurodegenerative disorders; hereditary disorders; and symptomatic causes, such as structural lesions, infections, metabolic abnormalities, hydrocephalus, and drugs or toxins. A good history of symptom evaluation, drug use, and family illness is just as essential as a careful neurologic examination when evaluating a patient with parkinsonism. Although there is no definitive diagnostic test for PD at this time, tests to rule out other causes should be considered and then treatment started.

Mitochondrial pathology in human schizophrenic striatum: a postmortem ultrastructural study

Studies using in vivo imaging or microscopic analysis of autopsy specimens indicate abnormalities in the striatum of schizophrenics including lower striatal metabolism, a change which can be normalized by antipsychotic medication. To investigate the possibility that abnormalities in schizophrenia brain may be due, in part, to pathology in mitochondria, organelles which generate energy, postmortem brain tissue from schizophrenic and control cases was obtained from the Maryland Brain Collection. Mitochondria in electron micrographs of striatal neuropil were counted and digitized. The caudate and the putamen of the schizophrenic subjects contained significantly (P < 0.05) fewer (a decrease of approximately 20%) mitochondrial profiles throughout the neuropil than did normal controls. The numbers of mitochondrial profiles per axon terminal appeared lower in the subset of schizophrenics off-drug as compared to either the subset of schizophrenics on-drug or to controls, suggesting that neuroleptic treatment may normalize this measure. The structural integrity of mitochondrial profiles in the schizophrenic striata was not obviously different from that of controls. Fewer mitochondrial profiles suggest decreased energy demands or diminished capacity to respond to energy requirements in the structures that contain them. These data are consistent with other studies showing decreased metabolism in the striatum of schizophrenics and may identify, in part, the anatomical basis of this deficit.

The relationship between oral dyskinesias produced by long-term haloperidol treatment, the density of striatal preproenkephalin messenger RNA and enkephalin peptide, and the number of striatal neurons expressing preproenkephalin messenger RNA in rats

Neuroleptic-induced oral dyskinesias in rats, a putative analogue to human tardive dyskinesia, may be due to excitotoxic degeneration within the striatum. Haloperidol treatment for 34 weeks increased the optical density of preproenkephalin messenger RNA in individual striatal neurons and enkephalin peptide in the neuropil, regardless of the level of oral dyskinesia produced. However, using unbiased stereological methods, an increased number of striatal neurons expressing preproenkephalin messenger RNA was observed only in rats that did not develop pronounced oral dyskinesias during haloperidol treatment. Said in another manner, the haloperidol-treated animals that developed pronounced oral dyskinesias, failed to produce an increase in the number of neurons expressing preproenkephalin messenger RNA. These results indicate that the mechanism by which neuroleptics induce oral dyskinesias in rats, and perhaps tardive dyskinesia in humans, involves a functional disturbance or even damage to a subpopulation of enkephalinergic neurons in the striatum.

Oral Dyskinesias and striatal lesions in rats after long-term co-treatment with haloperidol and 3-nitropropionic acid

The pathophysiologic basis of tardive dyskinesia remains unclear. It has been proposed that tardive dyskinesia may be a result of excitotoxic neurodegeneration in the striatum caused by a neuroleptic-induced increase in striatal glutamate release and impaired energy metabolism. To investigate this hypothesis, haloperidol decanoate (38 mg/kg/four weeks intramuscularly) and the succinate dehydrogenase inhibitor 3-nitropropionic acid (8 mg/kg/day via subcutaneous osmotic mini-pumps), were administered alone or together for 16 weeks to four-months-old rats. Control rats received sesame oil intramuscularly and had empty plastic tubes subcutaneously. Vacuous chewing movements, a putative analogue to human tardive dyskinesia, were recorded during and after drug treatment. Haloperidol alone, 3-nitropropionic acid alone, and 3-nitropropionic acid+haloperidol treatments induced an increase in vacuous chewing movements. However, vacuous chewing movements were more pronounced and appeared earlier in rats treated with 3-nitropropionic acid+haloperidol. After drug withdrawal, increases in vacuous chewing movements persisted for 16 weeks in the haloperidol alone and 3-nitropropionic acid+haloperidol group and for four weeks in the 3-nitropropionic acid alone group. Brains from each group were analysed for histopathological alterations. Bilateral striatal lesions were present only in rats with high levels of vacuous chewing movements in the 3-nitropropionic acid+haloperidol-treated rats. Nerve cell depletion and astrogliosis were prominent histopathologic features. There was selective neuronal sparing of both large- and medium-sized aspiny striatal neurons. These results suggest that mild mitochondrial impairment in combination with neuroleptics results in striatal excitotoxic neurodegeneration which may underlie the development of persistent vacuous chewing movements in rats and possibly irreversible tardive dyskinesia in humans.

Inhibitors of NADH-ubiquinone reductase: an overview

This article provides an updated overview of the plethora of complex I inhibitors. The inhibitors are presented within the broad categories of natural and commercial compounds and their potency is related to that of rotenone, the classical inhibitor of complex I. Among commercial products, particular attention is dedicated to inhibitors of pharmacological or toxicological relevance. The compounds that inhibit the NADH-ubiquinone reductase activity of complex I are classified according to three fundamental types of action on the basis of available evidence and recent insights: type A are antagonists of the ubiquinone substrate, type B displace the ubisemiquinone intermediate, and type C are antagonists of the ubiquinol product.

Haloperidol induces persistent down-regulation of tyrosine hydroxylase immunoreactivity in substantia nigra but not ventral tegmental area in the rat

The dopamine antagonist haloperidol can cause tardive side-effects that may persist after the drug is withdrawn. We studied the time course of changes in dopaminergic neurons of the substantia nigra and ventral tegmental area following withdrawal of haloperidol. Rats received daily intraperitoneal injections of saline or haloperidol for eight weeks and were killed at two, four or 12 weeks after the final injection. Sections of substantia nigra and ventral tegmental area were processed for tyrosine hydroxylase immunohistochemistry. Quantitative morphometric analysis was carried out blinded in order to determine the number, cell body size and topography of tyrosine hydroxylase-positive cells, and the immunoreactive area of the substantia nigra and ventral tegmental area. In haloperidol-treated rats, tyrosine hydroxylase-positive cell counts were normal in ventral tegmental area but were decreased in substantia nigra by 34% at two weeks withdrawal and by 52% at four weeks withdrawal; cell counts were almost fully recovered by 12 weeks withdrawal. Cross-sectional area of tyrosine hydroxylase immunoreactivity within the substantia nigra demonstrated a similar pattern of reduction, with full recovery by 12 weeks withdrawal. Mean cell size, by contrast, was essentially unchanged at two and four weeks withdrawal, but was significantly decreased in sub-regions of substantia nigra at 12 weeks withdrawal. These results indicate that haloperidol can produce selective changes in midbrain dopamine neurons that persist long after discontinuation of the drug. This decrease in tyrosine hydroxylase-immunoreactive cell counts may play a role in the neurobiology of the persistent tardive syndromes associated with the use of neuroleptics.

Mitochondrial dysfunction in idiopathic Parkinson disease

Disordered mitochondrial metabolism may play an important role in a number of idiopathic neurodegenerative disorders. The question of mitochondrial dysfunction is particularly attractive in the case of idiopathic Parkinson disease (PD), since Vyas et al. recognized in the 1980s that the parkinsonism-inducing compound N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine is a mitochondrial toxin. The unique genetic properties of mitochondria also make them worthy of consideration for a pathogenic role in PD, as well as in other late-onset, sporadic neurodegenerative disorders. Although affected persons occasionally do provide family histories that suggest Mendelian inheritance, the vast majority of the time these diseases appear sporadically. Because of unique features such as heteroplasmy, replicative segregation, and threshold effects, mitochondrial inheritance can allow for the apparent sporadic nature of these diseases.

Drug-induced movement disorders

Drug-induced movement disorders are often unrecognized, especially when not due to dopamine receptor blockers. This review discusses acute, subacute, and chronic syndromes. Pathophysiology relates almost always to dopaminergic transmission. Patient-dependent vulnerability and drug-dependent sensitivity are contributing factors. Young patients are more prone to acute reactions, and tardive or chronic conditions are more frequent in the elderly. Subclinical Parkinsonism can be unmasked by medication exposure. Treatment of tardive dyskinesia remains a challenging task for the clinician, but novel antipsychotics and dopamine depleting agents can be beneficial.

Review of functional magnetic resonance imaging in schizophrenia

Functional magnetic resonance imaging (fMRI) holds great promise for assessing temporal changes in brain activity using various challenge paradigms. In this report, we review the 14 studies (eight of them abstracts) that comprise the fMRI literature available to date relating to schizophrenia. Twelve of the 14 investigations examined changes in blood-oxygen-level-dependent (BOLD) contrast: two examined blood volume. Eight of the 12 BOLD studies relied on lower-order cognitive processing to measure activation (involving sensory or motor areas), whereas four used higher-order tasks (word production, auditory processing, and subspan word recall involving multiple brain areas). Although the variability in tasks used, brain regions studied, imaging methods used, patient characteristics reported, and methods of reporting significance precluded a full meta-analysis, we re-analyzed these published data to compute effect sizes. In most studies, resting blood volume and BOLD changes, regardless of the complexity of the cognitive task, appeared to differ between patients with schizophrenia and control subjects.

Intrastriatal neurotoxin injections reduce in vitro and in vivo binding of radiolabeled rotenoids to mitochondrial complex I

The in vivo and in vitro bindings of radiolabeled rotenoids to mitochondrial complex I of rat striatum were examined after unilateral intrastriatal injections of quinolinic acid or 1-methyl-4-phenylpyridinium salt (MPP+). Quinolinic acid produced significant, similar losses of in vivo binding of [11C]dihydrorotenol ([11C]DHROL: 40%) and in vitro binding of [3H]dihydrorotenone ([3H]DHR: 53%) in the injected striatal at 13 days after the injection of neurotoxin. MPP+ reduced in vivo binding of [11C]DHROL up to-55%) as measured 1.5 to 6 h after its administration. Reductions of in vivo [11C]DHROL binding after either quinolinic acid or MPP+ injections did not correlate with changes in striatal blood flow as measured with [14C]iodoantipyrine. These results are consistent with losses of complex I binding sites for radiolabeled rotenoids, produced using cell death (quinolinic acid) or direct competition for the binding site (MPP+). Appropriately radiolabeled rotenoids may be useful for in vivo imaging studies of changes of complex I in neurodegenerative diseases.

Dopamine-glutamate interactions in the striatum: behaviourally relevant modification of excitotoxicity by dopamine receptor-mediated mechanisms

The two most important afferent projections to the striatum contain glutamate and dopamine, respectively. Excitotoxic damage resulting from excessive stimulation of the N-methyl-D-aspartate subtype of glutamate receptor has been implicated in pathophysiology of ischaemic stroke, hypoglycaemic brain damage and Huntington's disease. We studied the ability of the dopamine system to modify the anatomical, neurochemical and behavioural consequences of glutamatergic toxicity in the striatum. In a first set of experiments, the specific N-methyl-D-aspartate receptor agonist quinolinate was injected unilaterally into the striatum of rats pretreated with one of (i) intraperitoneal (i.p.) saline (controls); (ii) i.p. haloperidol, a D2 dopamine receptor agonist; or (iii) 6-hydroxydopamine lesion of the ipsilateral nigrostriatal tract. Quinolinate-induced striatal damage, as assessed by morphometric and neurochemical criteria, was significantly attenuated in the animals with 6-hydroxydopamine lesions and in those pretreated with haloperidol, compared with saline-pretreated controls. There were no significant differences between the 6-OHDA and haloperidol groups. In a second set of experiments, animals received (i) bilateral intrastriatal quinolinate plus perioperative i.p. saline; (ii) bilateral intrastriatal quinolinate plus i.p. haloperidol; or (iii) bilateral intrastriatal saline. Again, the quinolinate-lesioned animals treated with perioperative haloperidol had significantly less striatal damage than the bilateral quinolinate rats. Behavioural assessment in the Morris Water Maze showed the bilateral quinolinate+haloperidol group to be significantly less impaired on a spatial acquisition task than the bilateral quinolinate animals. Measures of spontaneous daytime motor activity showed significant differences in average speed and rest time between the bilateral quinolinate+haloperidol rats and the bilateral quinolinate group. The performance of the bilateral quinolinate+haloperidol group was not significantly different from that of controls on any of the behavioural tasks. These results indicate an important role for D2 dopamine receptor-mediated mechanisms in striatal excitotoxicity. Since the excitotoxic process involves the same fundamental signalling mechanism that is involved in normal glutamatergic transmission, these findings imply an ability of D2 receptor blockade to modify glutamate signalling in the striatum. These results may have implications for treatment strategies in ischaemic stroke, hypoglycaemic brain damage and schizophrenia.

Inhibition by memantine of the development of persistent oral dyskinesias induced by long-term haloperidol treatment of rats

1. Tardive dyskinesia (TD) is a serious side-effect of long-term treatment with neuroleptics. To investigate if neuroleptic-induced excessive stimulation of striatal glutamate receptors may underlie TD development, the effect of the NMDA antagonist, memantine (1-amino-3,5-dimethyladamantane), was studied in a rat model of TD. 2. In an acute experiment, six groups of rats were treated daily for 1 week with either vehicle or memantine 20 or 40 mg kg-1 day-1, and on the seventh day they received one injection of either haloperidol 1.0 mg kg-1 i.p. or saline i.p. In a subsequent long-term experiment lasting 20 weeks, the same treatment was continued, except that haloperidol was injected i.m. as decanoate (38 mg kg-1 every 4 weeks) and control rats received sesame oil. The behaviour was videotaped and scored at intervals during both experiments, and for 16 weeks after cessation of the long-term treatment. 3. In the acute experiment, haloperidol decreased motor activity and memantine increased moving and tended to attenuate the immobility induced by haloperidol. Memantine also enhanced the haloperidol-induced increase in the putative TD-analogue vacuous chewing movements (VCM). 4. In the long-term experiment, the most marked effect of haloperidol was a gradual increase in VCM and the increase persisted significantly for 12 weeks after cessation of treatment. Memantine dose-dependently increased VCM and moving during long-term treatment. However, only one week after stopping treatment, both these effects of memantine disappeared. In contrast to rats previously treated with haloperidol alone, rats co-treated with memantine (both doses) and haloperidol had VCM at the level of controls two weeks after stopping treatment. The blood levels of drugs were within the therapeutic range achieved in human subjects. 5. These results suggest that long-lasting changes induced by haloperidol are prevented by memantine, which supports the theory that excessive NMDA receptor stimulation may be a mechanism underlying the development of persistent VCM in rats and maybe also TD in human subjects.

Mitochondrial generation of reactive oxygen species after brain ischemia in the rat

BACKGROUND AND PURPOSE

Brain mitochondria have a substantial capacity to generate reactive oxygen species after ischemia when the components of the respiratory chain are reduced and molecular oxygen is present. We tested the hypothesis that brain mitochondria in vivo produce reactive oxygen species after ischemia/reperfusion (IR) in rats at a rate sufficient to escape endogenous antioxidant defenses.

METHODS

Ischemia-dependent production of hydroxyl radical in the hippocampus of the anesthetized rat was monitored with the use of intracerebral microdialysis. Transient global ischemia was produced by bilateral carotid artery occlusion and hemorrhagic hypotension to a mean arterial pressure of 35 mm Hg for 15 minutes followed by reperfusion for 60 minutes. Salicylic acid was infused into the hippocampus during the experiments, and changes in the recovery of its hydroxylated product, 2,3-dihydroxybenzoic acid (2,3-DHBA), were used to assess the effects of inhibitors of mitochondrial complex I on formation of hydroxyl radical during IR. Hydroxylation data from control groups of animals were compared with data from animals undergoing IR during treatment with either a mitochondrial complex I inhibitor alone or the inhibitor plus succinic acid.

RESULTS

Transient ischemia led to a fivefold increase in the recovery of 2,3-DHBA by microdialysis after 1 hour relative to control animals (P < .05). Inhibition of mitochondrial complex I prevented 2,3-DHBA formation after IR; this effect could be reversed by infusion of succinic acid by microdialysis during IR.

CONCLUSIONS

The data indicate that reactive oxygen species generated by mitochondrial electron transport escape cellular antioxidant defenses and promote highly damaging hydroxyl radical activity after transient brain ischemia in the rat.

Ultrastructural correlates of haloperidol-induced oral dyskinesias in rat striatum

Neuroleptics given chronically to rats induce behavioral sequelae which mimic tardive dyskinesia in some respects. The intent of this study was to investigate the ultrastructural correlates of oral dyskinesias (vacuous chewing movements [VCMs]), induced by chronic haloperidol treatment. After 6 months of treatment, rats were divided into low or high VCM groups. Rats in the high VCM group were either sacrificed on drug or were withdrawn from drug for 4 weeks. Ultrastructural analyses of the striatum indicated that synaptic density: 1) was significantly decreased in both the low and high VCM groups compared to normal controls; 2) was more profoundly decreased in the high VCM group as compared to the low VCM group; and 3) recovered to normal following drug withdrawal. Compared to controls, the density of asymmetric synapses was reduced by a similar magnitude in both the low and high VCM groups, suggesting that this change is a result of haloperidol treatment and independent of VCMs. Conversely, the density of symmetric synapses was reduced compared to normal, only in the high VCM group, suggesting that this change is specifically related to the expression of VCMs. In addition, mitochondrial profiles were hypertrophied and less frequent in the high VCM group in comparison to controls; size, but not number, recovered following drug withdrawal. These results identify distinct ultrastructural correlates of chronic haloperidol treatment that are unique to rats that develop VCMs and suggest that these ultrastructural features may play a role in the pathophysiology of oral dyskinesias in rats.

Age- and peroxidative stress-related modifications of the cerebral enzymatic activities linked to mitochondria and the glutathione system

The aging brain undergoes a process of enhanced peroxidative stress, as shown by reports of altered membrane lipids, oxidized proteins, and damaged DNA. The aims of this review are to examine: (1) the possible contribution of mitochondrial processes to the formation and release of reactive oxygen species (ROS) in the aging brain; and (2) the age-related changes of antioxidant defenses, both enzymatic and nonenzymatic. It will focus on studies investigating the role of the electron transfer chain as the site of ROS formation in brain aging and the alterations of the glutathione system, also in relation to the effects of exogenous pro-oxidant agents. The possible role of peroxidative stress in age-related neurodegenerative diseases will also be discussed.

Low platelet mitochondrial complex I and complex II/III activity in early untreated Parkinson's disease

Following the discovery of inhibition of electron transport complex 1 by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces a parkinsonian syndrome in humans, monkeys, and mice, several laboratories have reported abnormalities of complex I and other electron transport complexes (ETCs) in various tissues from patients with Parkinson's disease (PD). Criticism of the significance of these findings in the etiology of PD has centered on whether drug treatments or the debilitation of the disease process itself produced the low ETC activities. We present results from a blinded study of platelet mitochondrial ETC activities in 18 early untreated PD patients and 18 age- and sex-matched controls and in 13 spousal controls. Lower complex I activity in platelet mitochondria of PD patients was seen in early untreated disease and thus cannot be due to debilitation or drug therapy. Home environmental factors seem an unlikely explanation for the reduced complex I activity in PD patients but have not been excluded. Complex II/III activity was also reduced by 20% in PD compared with age-/sex-matched controls. The low complex I and II/III activities in platelet mitochondria appear to be related to the etiology of PD.

The mitochondrial toxin 3-nitropropionic acid induces vacuous chewing movements in rats. Implications for tardive dyskinesia?

Rats were chronically treated for 4 weeks with three doses (4, 8, 12 mg/kg per day) of the mitochondrial toxin 3-nitropropionic acid (3-NP). The behaviour was videotaped at intervals during and after treatment, and vacuous chewing movements (VCM), a putative analogue to tardive dyskinesia (TD), as well as the general behaviour were scored. During treatment, 3-NP dose-dependently increased VCM and dose-dependently reduced motor activity, which is similar to the behavioural effect of long-term neuroleptic treatment. The results may support the hypothesis that neuroleptic-induced impairment of energy metabolism, a potential excitotoxic mechanism, is involved in the development of VCM in rats and probably TD in humans.

Drug-induced parkinsonism: a review

The main clinical features, pathophysiology and underlying mechanisms of drug-induced parkinsonism are reviewed. The clinical manifestations of drug-induced parkinsonism are often indistinguishable from idiopathic Parkinson's disease. However, some subtle differences may exist: for example drug-induced parkinsonism is often associated with tardive dyskinesias, bilateral symptoms and the absence of resting tremor, etc. Besides toxins (eg manganese, carbon monoxide or MPTP), many drugs are known to produce parkinsonism: dopamine blocking drugs (true neuroleptics used as antipsychotics: phenothiazines, butyrophenones, thioxanthenes but also sulpiride, "hidden" neuroleptics prescribed as anti-nausea or anti-vomiting drugs (such as metoclopramide and other benzamide derivatives), dopamine depleting drugs (reserpine, tetrabenazine), alpha-methyldopa, calcium channel blockers (flunarizine, cinnarizine, etc). The putative role of other drugs (eg fluoxetine, lithium, amiodarone) as well as the therapeutic management of this side effect are reviewed.

Anti-glutamatergic effects of clozapine

Clozapine (Cz) is unique in its efficacy with treatment refractory patients and its freedom from motor side effects. The present work shows that Cz, even after dopamine depletion, suppresses responses evoked via the monosynaptic glutamatergic corticostriatal pathway. In addition, Cz is effective in displacing [3H]MK-801 from striatal homogenates. These data indicate that Cz is a glutamate antagonist. It is unclear, however, if this pharmacological action could explain Cz's lack of motor effects and it's antipsychotic potency.