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

Potential Crosstalk Between Parkinson's Disease and Energy Metabolism

Parkinson's disease (PD) is characterized by the accumulation of alpha-synuclein (α-Syn) in the substantia nigra (SN) and the degeneration of nigrostriatal dopaminergic (DAergic) neurons. Some studies have reported that the pathology of PD originates from the gastrointestinal (GI) tract, which also serves as an energy portal, and develops upward along the neural pathway to the central nervous system (CNS), including the dorsal motor nucleus of vagus (DMV), SN, and hypothalamus, which are also involved in energy metabolism control. Therefore, we discuss the alterations of nuclei that regulate energy metabolism in the development of PD. In addition, due to their anti-inflammatory, antiapoptotic and antioxidative roles, metabolism-related peptides are involved in the progression of PD. Furthermore, abnormal glucose and lipid metabolism are common in PD patients and exacerbate the pathological changes in PD. Therefore, in this review, we attempt to explain the correlation between PD and energy metabolism, which may provide possible strategies for PD treatment.

Protective role of endocannabinoid signaling in an animal model of haloperidol-induced tardive dyskinesia

Tardive dyskinesia (TD) is a side effect associated with the long-term use of certain antipsychotics. Considering the modulatory role of the endocannabinoid system upon dopaminergic neurotransmission, the present study tested the hypothesis that increasing endocannabinoid (anandamide and 2-arachidonoylglycerol) levels attenuates haloperidol-induced TD (vacuous chewing movements, VCMs) in male Wistar rats. The animals received administration of chronic haloperidol (38 mg/kg; 29 days) followed by acute FAAH (URB597, 0.1-0.5 mg/kg) or MAGL (JZL184, 1-10 mg/kg) inhibitors before VCM quantification. The underlying mechanisms were evaluated by pre-treatments with a CB₁ receptor antagonist (AM251, 1 mg/kg) or a TRPV₁ channel blocker (SB366791, 1 mg/kg). Moreover, CB₁ receptor expression was evaluated in the striatum of high-VCM animals. As expected, haloperidol induced VCMs only in a subset of rats. Either FAAH or MAGL inhibition reduced VCMs. These effects were prevented by CB₁ receptor antagonism, but not by TRPV1 blockage. Remarkably, CB₁ receptor expression was increased high-VCM rats, with a positive correlation between the levels of CB₁ expression and the number of VCMs. In conclusion, increasing endocannabinoid levels results in CB₁ receptor-mediated protection against haloperidol-induced TD in rats. The increased CB₁ receptor expression after chronic haloperidol treatment suggests a counter-regulatory protective mechanism.

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.

Genetics of tardive dyskinesia: Promising leads and ways forward

Tardive dyskinesia (TD) is a potentially irreversible and often debilitating movement disorder secondary to chronic use of dopamine receptor blocking medications. Genetic factors have been implicated in the etiology of TD. We therefore have reviewed the most promising genes associated with TD, including DRD2, DRD3, VMAT2, HSPG2, HTR2A, HTR2C, and SOD2. In addition, we present evidence supporting a role for these genes from preclinical models of TD. The current understanding of the etiogenesis of TD is discussed in the light of the recent approvals of valbenazine and deutetrabenazine, VMAT2 inhibitors, for treating TD.

Antipsychotic-induced Tardive dyskinesia: from biological basis to clinical management

INTRODUCTION

Tardive dyskinesia (TD) is a chronic and disabling movement disorder with a complex pathophysiological basis. A significant percentage of patients does not receive correct diagnosis, resulting in delayed or inaccurate treatment and poor outcome. Therefore, there is a critical need for prompt recognition, implementation of efficacious treatment regimens and long-term follow up of patients with TD. Areas covered: The current paper provides an overview of emerging data concerning proposed pathophysiology theories, epidemiology, risk factors, and therapeutic strategies for TD. Expert commentary: Despite considerable research efforts, TD remains a challenge in the treatment of psychosis as the available strategies remain sub-optimal. The best scenario will always be the prophylaxis or prevention of TD, which entails limiting the use of antipsychotics.

Behavioral and neurochemical effects induced by reserpine in mice

RATIONALE

Reserpine, a monoamine-depleting agent, which irreversibly and non-selectively blocks the vesicular monoamine transporter, has been used as an animal model to study several neurological disorders, including tardive dyskinesia and Parkinson's disease.

OBJECTIVE

The purpose of this study was to examine if motor deficits induced by reserpine in mice could be related to alterations in the expression of dopaminergic system proteins such as tyrosine hydroxylase (TH) and dopamine transporter (DAT) and in the activity of monoamine oxidase (MAO).

METHODS

Mice received either vehicle or reserpine (0.1, 0.5, or 1 mg/kg, s.c.) for four consecutive days. Two, 20, or 60 days after reserpine withdrawal, behavioral, and neurochemical changes were evaluated.

RESULTS

Reserpine at a dose of 0.5 and 1 mg/kg increased vacuous chewing movements (VCMs) and reduced locomotion. Behavioral changes were accompanied by reduction in TH immunoreactivity in the striatum evaluated on days 2 and 20 after the last injection of 1 mg/kg reserpine. Furthermore, negative correlations were found between VCM and MAO-A or MAO-B on day 2 and TH striatal immunoreactivity on day 20 after the last injection of 1 mg/kg reserpine. A positive correlation was observed between VCMs and DAT immunoreactivity in the substantia nigra on day 2 after the last injection of 0.5 mg/kg reserpine.

CONCLUSIONS

These findings suggest that the pharmacological blockage of vesicular monoamine transporter (VMAT) by reserpine caused neurochemical and behavioral alterations in mice.

Anandamide attenuates haloperidol-induced vacuous chewing movements in rats

Antipsychotics may cause tardive dyskinesia in humans and orofacial dyskinesia in rodents. Although the dopaminergic system has been implicated in these movement disorders, which involve the basal ganglia, their underlying pathomechanisms remain unclear. CB1 cannabinoid receptors are highly expressed in the basal ganglia, and a potential role for endocannabinoids in the control of basal ganglia-related movement disorders has been proposed. Therefore, this study investigated whether CB1 receptors are involved in haloperidol-induced orofacial dyskinesia in rats. Adult male rats were treated for four weeks with haloperidol decanoate (38mg/kg, intramuscularly - i.m.). The effect of anandamide (6nmol, intracerebroventricularly - i.c.v.) and/or the CB1 receptor antagonist SR141716A (30μg, i.c.v.) on haloperidol-induced vacuous chewing movements (VCMs) was assessed 28days after the start of the haloperidol treatment. Anandamide reversed haloperidol-induced VCMs; SR141716A (30μg, i.c.v.) did not alter haloperidol-induced VCM per se but prevented the effect of anandamide on VCM in rats. These results suggest that CB1 receptors may prevent haloperidol-induced VCMs in rats, implicating CB1 receptor-mediated cannabinoid signaling in orofacial dyskinesia.

New and emerging treatments for symptomatic tardive dyskinesia

The aim of this review is to assess new, emerging, and experimental treatment options for tardive dyskinesia (TD). The methods to obtain relevant studies for review included a MEDLINE search and a review of studies in English, along with checking reference lists of articles. The leading explanatory models of TD development include dopamine receptor supersensitivity, GABA depletion, cholinergic deficiency, neurotoxicity, oxidative stress, changes in synaptic plasticity, and defective neuroadaptive signaling. As such, a wide range of treatment options are available. To provide a complete summary of choices we review atypical antipsychotics along with resveratrol, botulinum toxin, Ginkgo biloba, tetrabenazine, clonazepam, melatonin, essential fatty acids, zonisamide, levetiracetam, branched-chain amino acids, drug combinations, and invasive surgical treatments. There is currently no US Food and Drug Administration-approved treatment for TD; however, prudent use of atypical antipsychotics with routine monitoring remain the cornerstone of therapy, with experimental treatment options available for further management.

Dual effects of L-DOPA on nigral dopaminergic neurons

L-DOPA (Levodopa) remains the gold standard for the treatment of motor symptoms of Parkinson's disease (PD), despite indications that the drug may have detrimental effects in cell culture. Classically, l-DOPA increases the production of dopamine (DA) in nigral dopaminergic neurons, while paradoxically inhibiting the firing of these neurons due to activation of D2 autoreceptors by extracellularly released DA. Using a combination of electrophysiology and calcium microfluorometry in brain slices, we have identified a novel effect of L-DOPA on dopaminergic neurons when D2 receptors were blocked. Under these conditions, L-DOPA (0.03-3 mM) evoked an excitatory effect consisting of two components. The 'early' component observed during and immediately after application of the drug, was associated with increased firing, membrane depolarization and inward current. This excitatory response was strongly attenuated by CNQX (10 μM), pointing to the involvement of TOPA quinone, an auto-oxidation product of L-DOPA and a potent activator of AMPA/kainate receptors. The 'late' phase of excitation persisted >30 min after brief L-DOPA application and was not mediated by ionotropic glutamate receptors, nor by D1, α1-adrenergic, mGluR1 or GABAB receptors. It was eliminated by carbidopa, demonstrating its dependence on conversion of L-DOPA to DA. Exogenous DA (50 μM) also evoked a glutamate-receptor independent increase in firing and an inward current when D2 receptors were blocked. In voltage-clamped neurons, both L-DOPA and DA produced a long-lasting increase in [Ca(2+)]i which was unaffected by block of ionotropic glutamate receptors. These results demonstrate that L-DOPA has dual, inhibitory and excitatory, effects on nigral dopaminergic neurons, and suggest that the excitation and calcium rise may have long-lasting consequences for the activity and survival of these neurons when the expression or function of D2 receptors is impaired.

Gallic acid decreases vacuous chewing movements induced by reserpine in rats

Involuntary oral movements are present in several diseases and pharmacological conditions; however, their etiology and efficient treatments remain unclear. Gallic acid is a natural polyphenolic acid found in gall nuts, sumac, oak bark, tea leaves, grapes and wine, with potent antioxidant and antiapoptotic activity. Thus, the present study investigated the effects of gallic acid on vacuous chewing movements (VCMs) in an animal model induced by reserpine. Rats received either vehicle or reserpine (1mg/kg/day, s.c.) during three days, followed by treatment with water or different doses of gallic acid (4.5, 13.5 or 40.5mg/kg/day, p.o.) for three more days. As result, reserpine increased the number of VCMs in rats, and this effect was maintained for at least three days after its withdrawal. Gallic acid at two different doses (13.5 and 40.5mg/kg/day) has reduced VCMs in rats previously treated with reserpine. Furthermore, we investigated oxidative stress parameters (DCFH-DA oxidation, TBARS and thiol levels) and Na(+),K(+)-ATPase activity in striatum and cerebral cortex, however, no changes were observed. These findings show that gallic acid may have promissory use in the treatment of involuntary oral movements.

Brain activity and human unilateral chewing: an FMRI study

Brain mechanisms underlying mastication have been studied in non-human mammals but less so in humans. We used functional magnetic resonance imaging (fMRI) to evaluate brain activity in humans during gum chewing. Chewing was associated with activations in the cerebellum, motor cortex and caudate, cingulate, and brainstem. We also divided the 25-second chew-blocks into 5 segments of equal 5-second durations and evaluated activations within and between each of the 5 segments. This analysis revealed activation clusters unique to the initial segment, which may indicate brain regions involved with initiating chewing. Several clusters were uniquely activated during the last segment as well, which may represent brain regions involved with anticipatory or motor events associated with the end of the chew-block. In conclusion, this study provided evidence for specific brain areas associated with chewing in humans and demonstrated that brain activation patterns may dynamically change over the course of chewing sequences.

Parallels between behavioral and neurochemical variability in the rat vacuous chewing movement model of tardive dyskinesia

The widely accepted rat vacuous chewing movement model for tardive dyskinesia could be more fully mined through greater focus on individual variability in vulnerability to this neuroleptic-induced behavior. We have examined parallels between behavioral and neurobiological variability within a cohort in order to evaluate the role that neurobiological factors might play in determining susceptibility to tardive dyskinesia. Inter-observer reliability and individual consistency across time, in both spontaneous and neuroleptic-induced vacuous chewing movements, were empirically demonstrated. While this behavior increased across 8 months of observation in both vehicle controls and haloperidol-treated rats, pre-treatment baselines were predictive of final levels across individuals only in the vehicle control group, not the haloperidol-treated group. Haloperidol-induced elevations in neostriatal D2 and GAD(67) mRNA were not correlated with individual variability in haloperidol-induced vacuous chewing movements. Ambient noise during the observations was found to exacerbate chronic haloperidol-induced, but not spontaneous vacuous chewing movements. Significant correlations were found among the haloperidol-treated rats between nigral and tegmental GAD(67) and tegmental α7 mRNA levels, measured by in situ hybridization histochemistry, and vacuous chewing movements, specifically in the noisy conditions. Variability in these secondary responses to primary striatal dopamine and GABA perturbations may play a role in determining vulnerability to vacuous chewing movements, and by analogy, tardive dyskinesia. Both the differential predictive value of baseline vacuous chewing movements and the differential effect of noise, between controls and haloperidol-treated rats, add to evidence that haloperidol-induced vacuous chewing movements are regulated, in part, by different mechanisms than those mediating spontaneous vacuous chewing movements.

Relevance of animal models to human tardive dyskinesia

Tardive dyskinesia remains an elusive and significant clinical entity that can possibly be understood via experimentation with animal models. We conducted a literature review on tardive dyskinesia modeling. Subchronic antipsychotic drug exposure is a standard approach to model tardive dyskinesia in rodents. Vacuous chewing movements constitute the most common pattern of expression of purposeless oral movements and represent an impermanent response, with individual and strain susceptibility differences. Transgenic mice are also used to address the contribution of adaptive and maladaptive signals induced during antipsychotic drug exposure. An emphasis on non-human primate modeling is proposed, and past experimental observations reviewed in various monkey species. Rodent and primate models are complementary, but the non-human primate model appears more convincingly similar to the human condition and better suited to address therapeutic issues against tardive dyskinesia.

Chronic treatment of haloperidol induces pathological changes in striatal neurons of guinea pigs: a light and electron microscopical study

In the present work, we investigated whether there would be any change in histological structure of striatal neurons after haloperidol applications at different doses. Adult male guinea pigs were treated once-daily with saline (group 4, control) or haloperidol during 6 weeks, and the dose was 1, 2, or 3 mg/kg (groups 1, 2, and 3, respectively). After treatment, all animals were anesthetized and striata were dissected and examined. When striata were evaluated histologically, dark neurons and some degenerating striatal neurons had distinctive morphological changes consistent with cell death, including reduced neuronal size with nuclear and cytoplasmic shrinkage. Also, in sections of striata in groups 1 and 2, but not in group 3, more glial cells were observed than in those of the control group. In all treated groups, fibrous content of intersititium was paralelly increased by increasing dose. Ultrastructural investigation of striatal neurons in haloperidol-treated rats showed notched nuclei and many lysosomes. Moreover, degeneration of myelin, scarce microglial macrophages, expansion of nuclear intermembranous space, degenerated mitochondria, and vacuoles were found. Also, cytoplasmic swelling, lysosomes, and apoptotic bodies were present. These results suggest that haloperidol treatment may lead to damage in neurons via the necrotic process in both low- and high-dose applications.

Nicotine reduces antipsychotic-induced orofacial dyskinesia in rats

Antipsychotics are an important class of drugs for the management of schizophrenia and other psychotic disorders. They act by blocking dopamine receptors; however, because these receptors are present throughout the brain, prolonged antipsychotic use also leads to serious side effects. These include tardive dyskinesia, repetitive abnormal involuntary movements of the face and limbs for which there is little treatment. In this study, we investigated whether nicotine administration could reduce tardive dyskinesia because nicotine attenuates other drug-induced abnormal movements. We used a well established model of tardive dyskinesia in which rats injected with the commonly used antipsychotic haloperidol develop vacuous chewing movements (VCMs) that resemble human orofacial dyskinesias. Rats were first administered nicotine (minipump; 2 mg/kg per day). Two weeks later, they were given haloperidol (1 mg/kg s.c.) once daily. Nicotine treatment reduced haloperidol-induced VCMs by ∼20% after 5 weeks, with a significant ∼60% decline after 13 weeks. There was no worsening of haloperidol-induced catalepsy. To understand the molecular basis for this improvement, we measured the striatal dopamine transporter and nicotinic acetylcholine receptors (nAChRs). Both haloperidol and nicotine treatment decreased the transporter and α6β2* nAChRs (the asterisk indicates the possible presence of other nicotinic subunits in the receptor complex) when given alone, with no further decline with combined drug treatment. By contrast, nicotine alone increased, while haloperidol reduced α4β2* nAChRs in both vehicle and haloperidol-treated rats. These data suggest that molecular mechanisms other than those directly linked to the transporter and nAChRs underlie the nicotine-mediated improvement in haloperidol-induced VCMs in rats. The present results are the first to suggest that nicotine may be useful for improving the tardive dyskinesia associated with antipsychotic use.

Deep brain stimulation of the subthalamic or entopeduncular nucleus attenuates vacuous chewing movements in a rodent model of tardive dyskinesia

Deep brain stimulation (DBS) has recently emerged as a potential intervention for treatment-resistant tardive dyskinesia (TD). Despite promising case reports, no consensus exists as yet regarding optimal stimulation parameters or neuroanatomical target for DBS in TD. Here we report the use of DBS in an animal model of TD. We applied DBS (100 μA) acutely to the entopeduncular nucleus (EPN) or subthalamic nucleus (STN) in rats with well established vacuous chewing movements (VCMs) induced by 12 weeks of haloperidol (HAL) treatment. Stimulation of the STN or EPN resulted in significant reductions in VCM counts at frequencies of 30, 60 or 130 Hz. In the STN DBS groups, effects were significantly more pronounced at 130 Hz than at lower frequencies, whereas at the EPN the three frequencies were equipotent. Unilateral stimulation at 130 Hz was also effective when applied to either nucleus. These results suggest that stimulation of either the EPN or STN significantly alleviates oral dyskinesias induced by chronic HAL. The chronic HAL VCM model preparation may be useful to explore mechanisms underlying DBS effects in drug-induced dyskinesias.

Effects of omega-3 essential fatty acids (omega-3 EFAs) on motor disorders and memory dysfunction typical neuroleptic-induced: behavioral and biochemical parameter

The effects of fish oil supplementation on motor disorders, memory dysfunction, and lipid peroxidation (LP) induced by typical neuroleptics were studied. Wistar rats received a suspension prepared with fish oil containing omega-3 fatty acids, water, and Tween 80 (1%) in the place of drinking water (FO group) or vehicle (C group) for 8 weeks. After 4 weeks of treatment, half of the animals of both groups were treated with haloperidol (H and FO + H groups; experiment 1), fluphenazine (F and FO + F groups; experiment 2), or vehicle (C group), administered once a week (12 mg/kg/im) for 4 weeks, maintaining the treatment with FO. Extrapyramidal motor disorders by haloperidol and fluphenazine were observed by an increase in vacuous chewing movements and catalepsy (P < 0.05). These effects were reduced by FO treatment (P < 0.05). Both neuroleptics displayed impairment in memory retention observed by latency time to find the original location of platform in water-maze task, after 4 days of training performed in the last treatment week. This effect was reduced by FO (P < 0.05) to both haloperidol and fluphenazine treatments. Haloperidol increased the LP in plasma and hippocampus, and these effects were decreased by FO treatment (P < 0.05). Fluphenazine increased the LP in plasma and substantia nigra, which were completely decreased by FO treatment (P < 0.05). The FO decreased the motor disorders, memory dysfunction, and oxidative damage typical neuroleptic-induced. Our results indicate that FO exhibits a neuroprotector role useful on diseases related to oxidative damages, and may be considered in the prevention of motor and memory side effects induced by the antipsychotic treatment.

Genetic study of BDNF, DRD3, and their interaction in tardive dyskinesia

Tardive dyskinesia (TD) is a neuroleptic-induced movement disorder. Its pathophysiology is unclear. The most consistent genetic findings have shown an association with the Ser9Gly polymorphism of the DRD3 gene. However, only few polymorphisms within DRD3 has been tested, and a comprehensive examination of DRD3 in TD is still lacking. Further, brain-derived neurotrophic factor (BDNF), a neuronal growth and survival peptide, regulates DRD3 expression and may be involved in the neuronal degeneration observed in TD. In the present study, we investigated 15 tag DRD3 polymorphisms and four tag BDNF polymorphisms for association with TD in our sample of Caucasian schizophrenia patients (N=171). While BDNF markers showed no association, a haplotype containing rs3732782, rs905568, and rs7620754 in the 5' region of DRD3 was associated with TD diagnosis (p[10,000 permutations]=0.007). We also found evidence of interaction between BDNF and DRD3 polymorphisms. Further studies are needed to confirm these findings.

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.

Role of calcium-independent phospholipase A2 in cortex striatum thalamus cortex circuitry-enzyme inhibition causes vacuous chewing movements in rats

RATIONALE

High levels of calcium independent phospholipase A2 (iPLA2) are present in certain regions of the brain, including the cerebral cortex, striatum, and cerebellum (Ong et al. 2005).

OBJECTIVES

The present study was carried out to elucidate a possible role of the enzyme in the motor system.

METHODS

The selective iPLA2 inhibitor bromoenol lactone (BEL), the nonselective PLA2 inhibitor methyl arachidonyl fluorophosphonate (MAFP), and an antisense oligonucleotide were used to interfere with iPLA2 activity in various components of the motor system. Control animals received injections of carrier (phosphate buffered saline, PBS) at the same locations. The number of vacuous chewing movements (VCM) was counted from 1 to 14 days after injection.

RESULTS

Rats that received BEL and high-dose MAFP injections in the striatum, thalamus, and motor cortex, but not the cerebellum, showed significant increase in VCM, compared to those injected with PBS at these locations. BEL-induced VCM were blocked by intramuscular injections of the anticholinergic drug, benztropine. Increased VCM was also observed after intrastriatal injection of antisense oligonucleotide to iPLA2. The latter caused a decrease in striatal iPLA2 levels, confirming a role of decreased enzyme activity in the appearance of VCM.

CONCLUSIONS

These results suggest an important role for iPLA2 in the cortex-striatum-thalamus-cortex circuitry. It is postulated that VCM induced by iPLA2 inhibition may be a model of human parkinsonian tremor.

Valeriana officinalis does not alter the orofacial dyskinesia induced by haloperidol in rats: role of dopamine transporter

Chronic treatment with classical neuroleptics in humans can produce a serious side effect, known as tardive dyskinesia (TD). Here, we examined the effects of V. officinalis, a medicinal herb widely used as calming and sleep-promoting, in an animal model of orofacial dyskinesia (OD) induced by long-term treatment with haloperidol. Adult male rats were treated during 12 weeks with haloperidol decanoate (38 mg/kg, i.m., each 28 days) and with V. officinalis (in the drinking water). Vacuous chewing movements (VCMs), locomotor activity and plus maze performance were evaluated. Haloperidol treatment produced VCM in 40% of the treated rats and the concomitant treatment with V. officinalis did not alter either prevalence or intensity of VCMs. The treatment with V. officinalis increased the percentage of the time spent on open arm and the number of entries into open arm in the plus maze test. Furthermore, the treatment with haloperidol and/or V. officinalis decreased the locomotor activity in the open field test. We did not find any difference among the groups when oxidative stress parameters were evaluated. Haloperidol treatment significantly decreased [(3)H]-dopamine uptake in striatal slices and V. officinalis was not able to prevent this effect. Taken together, our data suggest a mechanism involving the reduction of dopamine transport in the maintenance of chronic VCMs in rats. Furthermore, chronic treatment with V. officinalis seems not produce any oxidative damage to central nervous system (CNS), but it also seems to be devoid of action to prevent VCM, at least in the dose used in this study.

Diphenyl diselenide decreases the prevalence of vacuous chewing movements induced by fluphenazine in rats

RATIONALE

Chronic treatment with neuroleptics causes, as a side effect, tardive dyskinesia in humans; however, the mechanisms involved in its pathophysiology remain unclear.

OBJECTIVES

The purpose of this study was to examine the effects of diphenyl diselenide, an organoselenium compound with antioxidant properties, in an animal model of vacuous chewing movements (VCMs) induced by long-term treatment with fluphenazine.

RESULTS

Adult male rats were treated during 24 weeks with fluphenazine (25 mg/kg, intramuscularly [i.m.], once every 21 days) and diphenyl diselenide (1 mg/kg, subcutaneously, three times a week). VCMs and body weight gain were quantified every 3 weeks. The fluphenazine treatment produced VCMs in the majority of the treated rats (87% after 24 weeks). Concomitant treatment with diphenyl diselenide decreased the prevalence of VCMs to 50%. Additionally, we separated the rats that developed or did not develop VCMs. We did not find any statistical differences among the groups when oxidative stress parameters were evaluated. Chronic fluphenazine treatment significantly decreased [(3)H]-dopamine uptake. Concomitant treatment with diphenyl diselenide was not able to prevent this decrease in those rats that developed VCMs.

CONCLUSIONS

Our data suggest that the reduction in dopamine transport can be a possible mechanism related to the maintenance of VCMs in rats. Moreover, diphenyl diselenide seems to be a promising pharmacological agent in the reduction in the prevalence of VCMs in rats.

Constantin von Economo's contribution to the understanding of movement disorders

Constantin von Economo's (CvE) main scientific achievements were his studies on the cytoarchitectonics of the cerebral cortex, sleep, and encephalitis lethargica (EL). He found a close relationship between motor symptoms and psychiatric and behavioral disorders in EL and postencephalitic Parkinsonism and identified the underlying neuropathology in the diencephalon and the brainstem. In agreement with Tretiakoff's findings in Parkinson's disease, CvE related postencephalitic Parkinsonism to neuronal loss in the substantia nigra. Several of CvE's early, less well-known publications also deal with the basal ganglia and movement disorders. He demonstrated in rabbits that the substantia nigra modulates automatization, coordination, and succession of masticatory movements and swallowing. In a study on the effects of experimental lesions of the cerebral peduncle in cats and monkeys, CvE hypothesized a corticotegmental pathway that maintains motor functions after pyramidal tract lesions. Recent studies have identified this pathway, which ends in the pedunculopontine nucleus. In a study on posthemiplegic chorea, CvE discussed various pathophysiological hypotheses that partly resemble modern concepts of chorea. In a clinicopathological study on Wilson's disease, CvE traced the striofugal fibers and visualized the basal ganglia outflow pathways. CvE was an outstanding multidisciplinary movement disorder specialist who contributed substantially to modern basal ganglia research.

Melatonin as pharmacologic support in burn patients: a proposed solution to thermal injury-related lymphocytopenia and oxidative damage

OBJECTIVE

To review the data that support the clinical use of melatonin in the treatment of burn patients, with special emphasis on the stimulation of the oxidative defense system, the immune system, circadian rhythm of sleep/wakefulness, and the reduction in the toxicity of therapeutic agents used in the treatment of burn victims.

DATA SOURCE

A MEDLINE/PubMed search from 1975 to July 2006 was conducted.

STUDY SELECTION

The screening of the literature was examined using the key words: burn patients, lymphocytopenia, skin oxidative stress, antioxidant, melatonin, and free radicals.

DATA EXTRACTION AND SYNTHESIS

Thermal injury often causes damage to multiple organs remote from the original burn wound and may lead to multiple organ failure. Animal models and burn patients exhibit elevated free radical generation that may be causative in the local wound response and in the development of burn shock and distant organ injury. The suppression of nonspecific resistance and the disturbance in the adaptive immune system makes burn patients vulnerable to infections. Moreover, there is loss of sleep and the toxicity produced by drugs habitually used in the clinic for burn patients. Melatonin is a powerful antioxidant and is a potent protective agent against damage after experimental thermal injury. Some actions of melatonin as a potential supportive pharmacologic agent in burn patients include its: role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes, reduction in proinflammatory cytokines, inhibition of adhesion molecules, chronobiotic effects, and reduction in the toxicity of the drugs used in protocols to treat thermal injury patients.

CONCLUSIONS

These combined actions of melatonin, along with its low toxicity and its ability to penetrate all morphophysiologic membranes, could make it a ubiquitously acting and highly beneficial molecule in burn patients.

Striatal and nigral COX-2 expression after chronic typical and atypical neuroleptic administration in rats

Haloperidol, but not clozapine, induces dopaminergic nigrostriatal degeneration. However, the mechanisms by which haloperidol causes neurotoxicity are not fully understood. An increase in cyclooxygenase-2 (COX-2) expression has been observed correlated with nigrostriatal degeneration. We investigated the modifications of striatal and nigral COX-2 expression induced by chronic haloperidol and clozapine administration. Rats were treated for 21 days with: haloperidol (1 mg/kg), clozapine (1 mg/kg) or saline. No significant differences were observed in striatal and nigral COX-2 expression between haloperidol and clozapine-treated animals. This observation might suggest that nigral COX-2 expression is not the underlying mechanisms involved in haloperidol-induced dopaminergic neurodegeneration.

Effects of Chronic Haloperidol and/or Clozapine on Oxidative Stress Parameters in Rat Brain

Decreased antioxidant activity is considered as one of the causes of tardive dyskinesia in schizophrenic patients in a prolonged neuroleptic treatment course. Haloperidol (HAL) has been hypothesized to increase oxidative stress, while clozapine (CLO) would produce less oxidative damage. The objective was to determine whether CLO for 28 days could reverse or attenuate HAL-induced oxidative damage in animals previously treated with HAL for 28 days. HAL significantly increased thiobarbituric acid reactive substances levels in the cortex (CX) and striatum and increased protein carbonyls in hippocampus (HP) and CX and this was not attenuated by CLO treatment. In the total radical trapping antioxidant parameter assay there was a decrease in the HP total antioxidant potential induced by HAL and by treatment with HAL + CLO. Our findings demonstrated that the atypical antipsychotic CLO could not revert oxidative damage caused by HAL.

The potential of melatonin in reducing morbidity-mortality after craniocerebral trauma

Craniocerebral trauma (CCT) is the most frequent cause of morbidity-mortality as a result of an accident. The probable origins and etiologies are multifactorial and include free radical formation and oxidative stress, the suppression of nonspecific resistance, lymphocytopenia (disorder in the adhesion and activation of cells), opportunistic infections, regional macro and microcirculatory alterations, disruptive sleep-wake cycles and toxicity caused by therapeutic agents. These pathogenic factors contribute to the unfavorable development of clinical symptoms as the disease progresses. Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine endogenously produced in the pineal gland and in other organs and it is protective agent against damage following CCT. Some of the actions of melatonin that support its pharmacological use after CCT include its role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes (e.g. superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase), inhibition of pro-inflammatory cytokines and activation-adhesion molecules which consequently reduces lymphocytopenia and infections by opportunistic organisms. The chronobiotic capacity of melatonin may also reset the natural circadian rhythm of sleep and wakefulness. Melatonin reduces the toxicity of the drugs used in the treatment of CCT and increases their efficacy. Finally, melatonin crosses the blood-brain barrier and reduces contusion volume and stabilizes cellular membranes preventing vasospasm and apoptosis of endothelial cells that occurs as a result of CCT.

Differential nigral expression of Bcl-2 protein family in chronically haloperidol and clozapine-treated rats: role in neurotoxicity and stereotyped behavior

Tardive dyskinesia (TD) is a syndrome characterized by repetitive involuntary movements induced by the administration of typical neuroleptics such as haloperidol. TD generally persists after haloperidol withdrawal indicating that haloperidol produces long-lasting changes in brain function. In contrast to the typicals, atypical medications, such as clozapine, have very low rates of TD. The mechanisms underlying drug-induced TD are poorly understood. We have investigated the role of nigral expression of the bcl-2 family of proteins on haloperidol-induced neurotoxicity. Rats were treated for 21 days with the following drugs: haloperidol (1 mg/kg), clozapine (1 mg/kg) or saline. After a 3-day washout period, apomorphine-induced stereotyped behavior was scored. Western blotting was performed to evaluate the nigral expression of the dopamine transporter (DAT), bax, bcl-x(L) and bcl-2 proteins. Haloperidol administration, but not clozapine, increased stereotyped behavior (p<0.01) in association with a decrease in striatal DAT expression (p<0.05). Haloperidol and clozapine treatment significantly decreased the nigral expression of bax (p<0.05, p<0.01, respectively). Neither treatment modified bcx(L) expression. Haloperidol increased (p<0.05), whereas clozapine did not significantly modify the nigral expression of bcl-2. Our results suggest that the increase in bcl-2 expression in the haloperidol-treated animals might be a compensatory mechanism that may reflect cellular damage induced by haloperidol in the dopaminergic neurons in the pars compacta of the substantia nigra.

Role of nigral NFkappaB p50 and p65 subunit expression in haloperidol-induced neurotoxicity and stereotyped behavior in rats

Long-term use of typical neuroleptics such as haloperidol may be limited by unwanted motor side effects like tardive dyskinesia (TD) characterized by repetitive involuntary movements, involving the mouth, face and tongue. TD generally persists after haloperidol withdrawal indicating long lasting changes in brain function that are no longer related to the presence of the drug. The precise mechanisms of the neuronal toxicity induced by haloperidol are poorly understood. Haloperidol has been shown to induce the expression of the transcription factor nuclear factor-kappaB (NFkappaB). NFkappaB resembles a heterodimer protein composed of a 50 and a 65 kDa subunits and the role of the NFkappaB subunits on haloperidol-induced toxicity remains still unknown. The aim of the present study is to investigate the role of the p65 and p50 subunits of NFkappaB on the toxicity induced by chronic haloperidol administration in an experimental model of TD. Rats were treated for 21 days with: haloperidol (1mg/kg), clozapine (1mg/kg) or saline. Apomorphine-induced stereotyped behavior was evaluated. Striatal expression of the dopamine transporter (DAT) and the nigral expression of the NFkappaB p65 and p50 subunits were measured by Western Blot. Haloperidol, but not clozapine, increased stereotyped behavior associated to a decreased striatal DAT expression (p<0.01). Haloperidol did not modify the nigral expression of the p65 subunit whereas clozapine decreased it (p<0.01). Both drugs induced a significant decrease in the nigral expression of the NFkappaB p50 (p<0.05 and p<0.01, respectively). The decrease in nigral expression of the p50 subunit may increase the vulnerability of the dopaminergic neurons to a possible neurotoxic effect of p65 subunits in the haloperidol-treated rats.

Multidose risperidone treatment evaluated in a rodent model of tardive dyskinesia

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

Effects of N-methyl-D-aspartate receptor antagonism on neuroleptic-induced orofacial dyskinesias

RATIONALE

Tardive dyskinesia is a syndrome of abnormal, involuntary movements, which occurs as a complication of long-term neuroleptic therapy. The pathophysiology of this potentially irreversible syndrome is still an enigma.

OBJECTIVE

The objective of the present study was to elucidate the role of N-methyl-D-aspartate (NMDA) receptor involvement in neuroleptic-induced orofacial dyskinesia in rats.

METHODS

Animals chronically treated with haloperidol for a period of 40 weeks exhibited significantly more vacuous chewing movements (VCMs), as compared to vehicle-treated controls. In a series of acute experiments, rats received: amantadine (10, 20, and 40 mg/kg i.p.), a low-affinity, uncompetitive NMDA-receptor antagonist (open channel blocker); dextrorphan (5, 10, and 20 mg/kg i.p.), an NMDA receptor channel antagonist; ifenprodil (2.5, 5, and 10 mg/kg i.p.), a noncompetitive allosteric NMDA receptor antagonist acting at the polyamine site; and Ro 25-6981 (2.5, 5, and 10 mg/kg i.p.), a potent and selective blocker of NMDA receptors which contain the NR2B subunit.

RESULTS

All the drugs tested, except dextrorphan, reduced VCMs and tongue protrusions with varying efficacies and side effects profiles. Ro 25-6981 was found significantly more potent than amantadine and ifenprodil in reducing VCMs and tongue protrusions at all doses tested, and at the higher dose, it completely eliminated orofacial dyskinesia (p<0.05).

CONCLUSIONS

These results suggest that NMDA receptors may play a significant role in the pathophysiology of tardive dyskinesia. Furthermore, antagonists showing selectivity for NMDA receptors containing the NR2B subunit may be particularly efficacious as novel therapeutic agents for the treatment of tardive dyskinesia and deserve further testing.

Effects of age on reserpine-induced orofacial dyskinesia and possible protection of diphenyl diselenide

Acute reserpine administration produces persistent oral dyskinesia in rats, an alleged animal model of tardive dyskinesia. The pathophysiology of the syndrome remains unclear, but experimental evidence suggests that neurodegeneration in the basal ganglia caused by oxidative stress plays a pivotal role in TD development. In this paper, the authors examined whether diphenyl diselenide, an organochalcogen with antioxidant properties, changes the behavioral and neurochemical effect of acute reserpine administration in old rats. The basal vacuous chewing movements (VCMs) and facial twitching (FT) duration was higher in old rats (15 months of age), when compared with adult rats (3 months of age; 0.01). Basal thiobarbituric acid-reactive species (TBARS) levels were increased only in the cortex of old rats, when compared to adult animals (p < .05). Reserpine injection (1mg/kg, s.c. for 3 days every other day) caused a significant increase on the tongue protusion (TP) frequency (p < .01) and facial twitching duration (p < .01) in old rats. Diphenyl diselenide (10 mg/kg, i.p. for 4 days, starting the day before reserpine) reversed only reserpine-induced TP increase (p < .01). Reserpine caused a significant increase in striatal TBARS levels (p < .01) and diselenide reversed (p < .01) the effect of reserpine on TBARS levels in the striatum. In subcortical parts, isolated reserpine or diselenide administration significantly increased (p < .01) the levels of TBARS, while simultaneous treatment with reserpine and diselenide reverted this effect (p < .01). The results of the present study confirmed the effects of age on orofacial dyskinesia. Diphenyl diselenide, an organochalcogen with antioxidant properties, showed modest effects on reserpine-induced orofacial dyskinesia. However, additional studies are still necessary to establish whether this compound can be considered an effective antioxidant in other models of neurotoxicity.