Reversal of reserpine-induced vacuous chewing movements in rats by melatonin: involvement of peripheral benzodiazepine receptors

Haloperidol-induced hypokinesia in rats is differentially affected by the light/dark phase, age, and melatonin

It has been well established that the striatal dopaminergic system is compromised with aging, namely D2 receptor function. Also well documented is the age related decline of the neurohormone, melatonin, in both humans and nonhuman animals. What has not been well studied is the possible interaction between the D2 receptor system and the age related decline in melatonin with its unmistakable pattern of synthesis and release exclusively during the dark phase. We tested the effect of the D2 antagonist, haloperidol (1.0 mg/kg ip), in adolescent (2 mo old) and adult rats (10 mo old) in the light (ZT3) and dark phases (ZT 15) in rats kept in a 12 L/12D cycle and the effect of exogenous melatonin (15 mg/kg ip/day x 4 days for a total of 60 mg/kg) on D2 antagonism. Using the bar test, measuring the extrapyramidal side-effect of hypokinesia, we report haloperidol to work differentially depending on both age and phase. Adult rats experienced the effect of the D2 antagonist in both the light and dark phases, while younger rats did not show hypokinetic affects in the dark. By manipulated lighting, we were able to restore the effect of haloperidol in younger rats in the dark phase. We also found ameliorating effects of melatonin lessening time on the bar after treatment with haloperidol, however, this effect was only found in older rats. These data demonstrate the importance of the light/dark cycle and age in the susceptibility of extrapyramidal effects with use of drugs that target D2 receptor function.

Oral Supplementation of Melatonin Protects against Fibromyalgia-Related Skeletal Muscle Alterations in Reserpine-Induced Myalgia Rats

Fibromyalgia is a chronic syndrome characterized by widespread musculoskeletal pain and an extensive array of other symptoms including disordered sleep, fatigue, depression and anxiety. Important factors involved in the pathogenic process of fibromyalgia are inflammation and oxidative stress, suggesting that ant-inflammatory and/or antioxidant supplementation might be effective in the management and modulation of this syndrome. Recent evidence suggests that melatonin may be suitable for this purpose due to its well known ant-inflammatory, antioxidant and analgesic effects. Thus, in the current study, the effects of the oral supplementation of melatonin against fibromyalgia-related skeletal muscle alterations were evaluated. In detail, 90 Sprague Dawley rats were randomly treated with reserpine, to reproduce the pathogenic process of fibromyalgia and thereafter they received melatonin. The animals treated with reserpine showed moderate alterations at hind limb skeletal muscles level and had difficulty in moving, together with significant morphological and ultrastructural alterations and expression of inflammatory and oxidative stress markers in the gastrocnemius muscle. Interestingly, melatonin, dose and/or time dependently, reduced the difficulties in spontaneous motor activity and the musculoskeletal morphostructural, inflammatory, and oxidative stress alterations. This study suggests that melatonin in vivo may be an effective tool in the management of fibromyalgia-related musculoskeletal morphofunctional damage.

Adjunctive Melatonin for Tardive Dyskinesia in Patients with Schizophrenia: A Meta-Analysis

Background

Tardive dyskinesia (TD) is characterized by abnormal and involuntary movements. Importantly, TD could cause considerable personal suffering and social and physical disabilities.

Aims

This meta-analysis based on randomized controlled trials (RCTs) systematically assessed the therapeutic effect and tolerability of melatonin for TD in schizophrenia.

Methods

A computerized and systematical search of both Chinese (Wanfang Data, Chinese National Knowledge Infrastructure (CNKI), SINOMED) and English (PubMed, PsycINFO, Embase, Cochrane Library databases) databases, from their inception until June 8, 2017, was conducted by two independent authors. The severity of TD symptoms were the primary outcome measure and analyzed using a random effects model by the Review Manager (RevMan) Version 5.3. Quality evaluation of included RCTs was conducted using the Cochrane risk of bias and Jadad scale. The GRADE (Grades of Recommendation, Assessment, Development, and Evaluation) system recommendation grading method was used to assess the overall quality level of meta-analytic outcomes.

Results

Four RCTs (n=130) were identified and analyzed. Three RCTs used double blind and 1 RCT used masked assessors using the Cochrane risk of bias, and 3 RCTs were rated as high quality based on Jadad scale. Compared with the control group, adjunctive melatonin was superior in reducing the severity of TD as measured by the Abnormal Involuntary Movement Scale (AIMS) (4 RCTs, n=130, weighted mean difference (WMD): -1.52 (95% confidence intervals (CI): -3.24, 0.20), p=0.08; I²=0%) although the improvement did not reach a significant level. The overall evidence quality of the improvement of TD symptoms, according to GRADE approach, was rated as “Low”. The data on the ADRs and cognitive effect were limited.

Conclusions

This meta-analysis shows that melatonin has potential for improving TD symptoms in schizophrenia. Future higher quality and larger RCTs are warranted to confirm the findings.

Ginkgo biloba leaf extract and alpha-tocopherol attenuate haloperidol-induced orofacial dyskinesia in rats: Possible implication of antiapoptotic mechanisms by preventing Bcl-2 decrease and Bax elevation

BACKGROUND

Tardive dyskinesia (TD) is a serious side effect of long-term administration of typical neuroleptics, such as haloperidol. The pathophysiology of TD remains unclear, but the experimental evidence suggests that free radical-induced neuronal apoptosis in the basal ganglia may play an important role.

PURPOSE

This study was to investigate changes in Bax and Bcl-2 expression levels in TD-associated brain regions and the effects of the antioxidant EGb761 on Bax and Bcl-2 levels in an animal model of TD.

METHODS

Thirty-two rats were randomly divided into four study groups: saline control (saline), haloperidol-alone (haloperidol), EGb761-haloperidol (EGb), and alpha-tocopherol-haloperidol (vitamin E). Rats were treated with daily intraperitoneal haloperidol injections (2 mg/kg/day) for 5 weeks. EGb761 (50 mg/kg/day) and alpha-tocopherol (20 mg/kg/day) were then administered for another 5 weeks during the withdrawal period. Behavioral assessments were performed, and Bax and Bcl-2 protein expression levels were immunohistochemically analyzed in four brain regions, including the prefrontal cortex, striatum, substantia nigra, and globus pallidum.

RESULTS

We found that increased vacuous chewing movements (VCMs) were associated with increased proapoptotic Bax protein expression, decreased antiapoptotic Bcl-2 protein expression, and an increased Bax/Bcl-2 ratio. EGb761 and alpha-tocopherol treatment reversed the increase in VCMs, decreased Bax expression, increased Bcl-2 expression, and decreased the Bax/Bcl-2 ratio.

CONCLUSIONS

These results demonstrate that long-term haloperidol administration may affect Bcl-2 protein family expression and promote neuronal apoptosis in the basal ganglia. In combination with their antioxidant capacity, EGb761 and alpha-tocopherol's antiapoptotic effects through Bcl-2 might account for the symptom improvement observed in haloperidol-induced TD rats.

Magnesium Supplementation Prevents and Reverses Experimentally Induced Movement Disturbances in Rats: Biochemical and Behavioral Parameters

Reserpine administration results in a predictable animal model of orofacial dyskinesia (OD) that has been largely used to access movement disturbances related to extrapyramidal oxidative damage. Here, OD was acutely induced by reserpine (two doses of 0.7 mg/kg subcutaneous (s.c.)), every other day for 3 days), which was administered after (experiment 1) and before (experiment 2) magnesium (Mg) supplementation (40 mg/kg/mL, peroral (p.o.)). In experiment 1, Mg was administered for 28 days before reserpine treatment, while in experiment 2, it was initiated 24 h after the last reserpine administration and was maintained for 10 consecutive days. Experiment 1 (prevention) showed that Mg supplementation was able to prevent reserpine-induced OD and catalepsy development. Mg was also able to prevent reactive species (RS) generation, thus preventing increase of protein carbonyl (PC) levels in both cortex and substantia nigra, but not in striatum. Experiment 2 (reversion) showed that Mg was able to decrease OD and catalepsy at all times assessed. In addition, Mg was able to decrease RS generation, with lower levels of PC in both cortex and striatum, but not in substantia nigra. These outcomes indicate that Mg is an important metal that should be present in the diet, since its intake is able to prevent and minimize the development of movement disorders closely related to oxidative damage in the extrapyramidal brain areas, such as OD.

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.

Possible anti-oxidant and neuroprotective mechanisms of zolpidem in attenuating typical anti-psychotic-induced orofacial dyskinesia: a biochemical and neurochemical study

Tardive dyskinesia is a serious motor side effect of chronic anti-psychotic therapy. The pathophysiology of this disabling and commonly irreversible movement disorder continues obscure and may be caused due to GABAergic hypofunction or increased oxidative damage and free radical generation. Chronic treatment with typical antipsychotics leads to the development of abnormal hyperkinetic orofacial movements (vacuous chewing movements, tongue protrusions and facial jerking) in rats and is widely accepted as the animal model for tardive dyskinesia. Zolpidem, a GABA-mimetic drug is structurally related to melatonin and has been reported to possess anti-oxidant and neuroprotective effects both in vivo and in vitro. The study was carried out to investigate whether zolpidem can be used in the treatment of typical anti-psychotic-induced orofacial dyskinesia. Chronic haloperidol (1 mg/kg, i.p. for 21 days) and chlorpromazine (5 mg/kg, i.p. for 21 days) treatment significantly induced orofacial hyperkinetic movements and zolpidem [N, N, 6-trimethyl-2-p-tolyl-imidazo (1, 2-a) pyridine 3-acetamideL-(+)] dose dependently (1, 2, 5 mg/kg i.p. for 21 days) reduced these haloperidol and chlorpromazine-induced hyperkinetic orofacial movements. Biochemical analysis revealed that haloperidol and chlorpromazine treatment significantly induced increase in lipid peroxidation and decrease in the levels of total nitric oxide levels, non-protein thiols (NPSH) and of anti-oxidant defense enzymes, superoxide dismutase (SOD) and catalase in the striatum of rat brain. Co-administration of zolpidem (1, 2, 5 mg/kg i.p. for 21 days) significantly reduced the lipid peroxidation and restored the non-protein thiols and total nitric oxide levels induced by chronic haloperidol and chlorpromazine treatment. It also significantly reversed the haloperidol and chlorpromazine-induced decrease in brain SOD and catalase activity. Neurochemical analysis (Neurotransmitter and their metabolite level estimation) revealed that haloperidol and chlorpromazine significantly decreased the dopamine, norepinephrine and serotonin levels in brain homogenates where as it caused a significant increase in the metabolite (VMA and HVA) levels in urine, which were significantly reversed by zolpidem at higher doses. Result of the present study support the therapeutic use of zolpidem in the treatment of typical anti-psychotic-induced orofacial dyskinesia.

Effects of diphenyl–diselenide on orofacial dyskinesia model in rats

Recently, we have described the beneficial effects of Diphenyl diselenide, an organochalcogen with glutathione peroxidase-like activity, on reserpine-induced orofacial dyskinesia in old rats. In this study, our aim was to examine the effects of diselenide on haloperidol-induced orofacial dyskinesia in rats. Male wistar rats received one single dose of Haloperidol decanoate (57 mg/kg/im) or control. After this dose, the animals received daily administration of diphenyl diselenide (1, 5 or 10 mg/kg/sc) or control, during 28 days. Twenty-four hours after the last diselenide or control solution injection, all the rats were observed for quantification of oral dyskinesia through the frequency of vacuous chewing movements (VCM) and tongue protrusion (TP) and the duration of facial twitching (FT). Haloperidol caused a significant increase in VCM, TP and FT observed in the 4 weekly evaluations (p<0.05). The co-administration of diselenide (5 mg/kg) reversed this effect for all the parameters in four behavioral sessions. The results of the present study demonstrate the possible protective activity of diphenyl diselenide on haloperidol-induced orofacial diskinesia. This effect is in accordance to the involvement of neurotoxicity in orofacial dyskinesia and suggest that studies be continued with new antioxidant compounds.

Effect of Withania somnifera root extract on reserpine-induced orofacial dyskinesia and cognitive dysfunction

Tardive dyskinesia is one of the major side effects of long-term neuroleptic treatment. The pathophysiology of this disabling and commonly irreversible movement disorder is still obscure. Vacuous chewing movements in rats are widely accepted as an animal model of tardive dyskinesia. Oxidative stress and products of lipid peroxidation are implicated in the pathophysiology of tardive dyskinesia. Repeated treatment with reserpine (1.0 mg/kg) on alternate days for a period of 5 days (days 1, 3 and 5) significantly induced vacuous chewing movements and tongue protrusions in rats. Chronic treatment with Withania somnifera root extract (Ws) for a period of 4 weeks to reserpine treated animals significantly and dose dependently (50 and 100 mg/kg) reduced the reserpine-induced vacuous chewing movements and tongue protrusions. Reserpine treated animals also showed poor retention of memory in the elevated plus maze task paradigm. Chronic Ws administration significantly reversed reserpine-induced retention deficits. Biochemical analysis revealed that chronic reserpine treatment significantly induced lipid peroxidation and decreased the glutathione (GSH) levels in the brains of rats. Chronic reserpine treated rats showed decreased levels of antioxidant defense enzymes, superoxide dismutase (SOD) and catalase. Chronic administration of Ws root extract dose dependently (50 and 100 mg/kg) and significantly reduced the lipid peroxidation and restored the decreased glutathione levels by chronic reserpine treatment. It also significantly reversed the reserpine-induced decrease in brain SOD and catalase levels in rats. The major findings of the present study indicate that oxidative stress might play an important role in the pathophysiology of reserpine-induced abnormal oral movements. In conclusion, Withania somnifera root extract could be a useful drug for the treatment of drug-induced dyskinesia.

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

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

Beneficial effects of vitamin C and vitamin E on reserpine-induced oral dyskinesia in rats: Critical role of striatal catalase activity

Oral dyskinesias are implicated in a series of neuropathologies and have been associated to an increase in oxidative stress. Several antioxidants, including vitamin E, decrease reserpine-induced oral dyskinesia (OD) in rodents and we have described a protective role of striatal catalase against the development of OD. The aim of this study was to verify the effects of vitamin C alone or in combination with vitamin E on reserpine-induced OD as well as to determine a possible role of catalase in the antidyskinetic property of these vitamins. Different doses of vitamin C attenuated reserpine-induced increase in OD. A similar treatment with an effective dose of vitamin C concomitant to an effective dose of vitamin E potentiated the antidyskinetic effect of both vitamins when administered alone. The administration of these vitamins alone produced an increase in striatal catalase activity that likewise was potentiated by their combined administration. In addition, the antidyskinetic property of vitamin E and vitamin C was abolished by a concomitant treatment with the catalase inhibitor aminotriazole. These results indicate a beneficial effect of these vitamins and reinforce the critical role of striatal catalase against the development of oral dyskinesias.

Effects of gabaergic drugs on reserpine-induced oral dyskinesia

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

Acute reserpine and subchronic haloperidol treatments change synaptosomal brain glutamate uptake and elicit orofacial dyskinesia in rats

Reserpine- and haloperidol-induced orofacial dyskinesia are putative animal models of tardive dyskinesia (TD) whose pathophysiology has been related to free radical generation and oxidative stress. In the present study, the authors induced orofacial dyskinesia by acute reserpine and subchronic haloperidol administration to rats. Reserpine injection (one dose of 1 mg/kg s.c.) every other day for 3 days caused a significant increase in vacuous chewing, tongue protrusion and duration of facial twitching, compared to the control. Haloperidol administration (one dose of 12 mg/kg once a week s.c.) for 4 weeks caused an increase in vacuous chewing, tongue protrusion and duration of facial twitching observed in four weekly evaluations. After the treatments and behavioral observation, glutamate uptake by segments of the brain was analyzed. A decreased glutamate uptake was observed in the subcortical parts of animals treated with reserpine and haloperidol, compared to the control. Importantly, a decrease in glutamate uptake correlates negatively with an increase in the incidence of orofacial diskinesia. These results indicate that early changes in glutamate transport may be related to the development of vacuous chewing movements in rats.

Effects of topiramate on oral dyskinesia induced by reserpine

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

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.

Circadian-dependent effect of melatonin on dopaminergic D2 antagonist-induced hypokinesia and agonist-induced stereotypies in rats

Although a melatonin/dopamine relationship has been well established in nonmotor systems wherein dopamine and melatonin share an antagonist relationship, less clear is the role melatonin may play in extrapyramidal dopaminergic function. Therefore, the purpose of the present experiments was to examine the relationship between melatonin and the dopaminergic D2 receptor system and behavior. Hypokinesia was induced in male Sprague-Dawley rats with fluphenazine (D2 antagonist, 0.4 mg/kg ip) and stereotypies with apomorphine (D2 agonist, 0.6 mg/kg sc) during the light (1200 h) and dark (2200 h) phases. As expected, fluphenazine induced severe hypokinesia during the light phase (482 +/- 176 s); however, unexpectedly, fluphenazine-induced hypokinesia during the dark was almost nonexistent (25 +/- 6 s). Furthermore, melatonin treatment (30 mg/kg ip) produced a strong interaction with fluphenazine in that it reduced fluphenazine-induced hypokinesia by nearly 80% in the light (112 +/- 45 s) but paradoxically increased the minimal fluphenazine-induced hypokinesia in the dark by more than 60% (70 +/- 17 s). Melatonin also reduced apomorphine-induced stereotypies by nearly 40% in the light but had no effect in the dark. Taken together, these data show (1) a strong and unexpected nocturnal effect of fluphenazine on hypokinesia and (2) provide support for an antagonistic melatonin/dopaminergic interaction in the context of motor behavior and D2 receptor function which appears to be critically dependent on the light/dark status of the dopaminergic system.

Reversal of Reserpine-Induced Orofacial Dyskinesia and Cognitive Dysfunction by Quercetin

Tardive dyskinesia (TD) is a serious neurological syndrome associated with long-term administration of neuroleptics to humans and experimental animals. The pathophysiology of this disabling and commonly irreversible movement disorder is still obscure. It may be caused by a loss of dopaminergic cells or may be due to free radicals as a product of high synaptic dopamine levels. Quercetin is a bioflavonoid with strong antioxidant properties. Repeated treatment with reserpine (1.0 mg/kg) on each other day for a period of 5 days (days 1, 3 and 5) significantly induced vacuous chewing movements (VCMs) and tongue protrusions (TPs) in rats. Chronic treatment with quercetin for a period of 4 weeks to reserpine-treated animals significantly and dose dependently (50 and 100 mg/kg) reduced the reserpine-induced VCMs and TPs. Reserpine-treated animals also showed poor retention of memory in elevated plus-maze task paradigm. Chronic quercetin administration significantly reversed reserpine-induced retention deficits. Biochemical analysis revealed that chronic reserpine treatment significantly induced lipid peroxidation and decreased the glutathione (GSH) levels in the brains of rats. Chronic reserpine-treated rats showed decreased levels of antioxidant defense enzymes, superoxide dismutase (SOD) and catalase. Chronic administration of quercetin dose dependently (50-100 mg/kg) and significantly reduced the lipid peroxidation and restored the decreased GSH levels by chronic reserpine treatment. It also significantly reversed the reserpine-induced decrease in brain SOD and catalase levels in rats. The results of the present study clearly indicated that quercetin has a protective role against reserpine-induced orofacial dyskinesia and memory impairment. Consequently, the use of quercetin as a therapeutic agent for the treatment of TD should be considered.

Melatonin for the treatment of tardive dyskinesia

OBJECTIVE

To review the available literature regarding the use of melatonin in the treatment of tardive dyskinesia (TD).

DATA SOURCES

Literature was identified through MEDLINE (1966-September 2002), PsycINFO (1967-September 2002), and references of relevant articles. Review articles, case reports/series, and animal and human studies were reviewed.

DATA SYNTHESIS

Melatonin has been investigated in TD based on its antioxidant properties. Animal studies and several human case series describe an association between melatonin and TD. Two recent, controlled studies evaluated the role of melatonin in the treatment of TD.

CONCLUSIONS

There is a paucity of data evaluating the use of melatonin in TD. Both of the controlled studies evaluating its use are limited by methodologic issues. Although the most recent trial did report a statistically significant improvement in TD with melatonin, these results are not considered to be clinically significant. There are inadequate data at the present time to support the use of melatonin in patients with TD.

Effects of valproic acid on an animal model of tardive dyskinesia

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

Effects of melatonin on behavioral dopaminergic supersensitivity

This study examines the effects of melatonin on dopaminergic supersensitivity induced by long-term treatment with haloperidol in rats. Enhancements of spontaneous general activity in an open-field and of stereotyped behavior induced by apomorphine after abrupt withdrawal from long-term treatment with haloperidol were used as experimental parameters for dopaminergic supersensitivity. Experiment 1 was conducted to investigate the effects of melatonin on the development of dopaminergic supersensitivity, and experiment 2 was conducted to investigate the effects of melatonin on the development as well as on expression of dopaminergic supersensitivity. Rats of both experiments were long-term treated with saline or haloperidol concomitant to saline or melatonin. In experiment 1 behavioral observations were performed after abrupt withdrawal from long-term treatment. In experiment 2 behavioral observations were performed 1 hour after an acute injection of saline or melatonin, administered after the abrupt withdrawal from long-term treatment. Both behavioral parameters used showed the development of central dopaminergic supersensitivity in rats treated with haloperidol since 24 hours after abrupt withdrawal. Concomitant treatment with melatonin intensified haloperidol-induced dopaminergic supersensitivity, observed 72 hours after withdrawal. Melatonin treatment per se also induced behavioral supersensitivity evaluated by both open-field and stereotyped behaviors, although it was more fugacious than that presented by haloperidol. Acute treatment with melatonin reverted the enhancement of the haloperidol-induced dopaminergic supersensitivity produced by concomitant long-term treatment with melatonin, as well as melatonin-induced dopaminergic supersensitivity per se. Our results support previous evidence of antidopaminergic effects of melatonin and demonstrate that repeated administration of this hormone modifies the plasticity of behaviors mediated by central dopaminergic systems.

Ebselen attenuates reserpine-induced orofacial dyskinesia and oxidative stress in rat striatum

Reserpine-induced orofacial dyskinesia is an alleged animal model of tardive dyskinesia whose pathophysiology has been related to striatal oxidative stress. In the present investigation, the authors examined whether ebselen, an antioxidant organochalcogen with glutathione peroxidase-like activity, changes the behavioral and neurochemical effect of acute reserpine administration. Reserpine injection for 3 days every other day caused a significant increase on the tongue protrusion frequency and ebselen (30 mg/kg ip for 4 days, starting 1 day before reserpine) reversed partially the effect of reserpine (P<.05). Reserpine- and reserpine+ebselen-treated groups displayed an increase in vacuous chewing frequency when compared to control and ebselen-treated groups (P<.05) Reserpine increased the duration of facial twitching and ebselen reversed partially the effect of reserpine (P<.01). Reserpine increased significantly the thiobarbituric acid-reactive species (TBARS) levels, and ebselen reversed the effect of reserpine on TBARS production in rat striatum. The results of the present study clearly indicated that ebselen has a protective role against reserpine-induced orofacial dyskinesia and reversed the increase in TBARS production caused by reserpine administration. Consequently, the use of ebselen as a therapeutic agent for the treatment of tardive dyskinesia should be considered.