Can the supersensitivity of rodents to dopamine be regarded as a model of tardive dyskinesia?

Synergistic anti-depressive effect of combination treatment of Brexpiprazole and selective serotonin reuptake inhibitors on forced swimming test in mice

AIM

Selective serotonin reuptake inhibitors (SSRIs) are used to treat major depressive disorder (MDD) and other psychiatric disorders (e.g., obsessive compulsive disorder, social anxiety disorder, and panic disorder). In MDD treatment, SSRIs do not show remission in approximately 30% of patients, indicating a need for a better treatment option. Forced swimming test (FST) is a behavioral assay to evaluate depression-like behavior and antidepressant efficacy in rodents. In the present study, we evaluated the combination effect of brexpiprazole with SSRIs on FST in mice, in order to investigate their synergistic effect.

METHODS

Brexpiprazole (0.003 mg/kg) was intraperitoneally injected to mice 15 min before testing. Escitalopram (10 mg/kg), fluoxetine (75 mg/kg), paroxetine (10 mg/kg), or sertraline (15 mg/kg) were orally administered to mice 60 min before testing. Then, the mice were placed in water and immobility time was measured. Data from animals treated with escitalopram, fluoxetine, paroxetine, and sertraline were pooled as SSRI-treated group data.

RESULTS

Combination treatment of brexpiprazole with SSRIs reduced immobility time in FST more than vehicle or each single treatment. A significant interaction effect was confirmed in the combination of brexpiprazole and SSRIs (p = 0.0411).

CONCLUSION

Efficacy of adjunctive brexpiprazole has already been demonstrated in clinical trials in MDD patients not adequately responding to antidepressants including escitalopram, fluoxetine, paroxetine, and sertraline. The synergistic antidepressant-like effect of brexpiprazole with SSRIs found in this study supports the already known clinical findings.

Brexpiprazole has a low risk of dopamine D2 receptor sensitization and inhibits rebound phenomena related to D2 and serotonin 5-HT2A receptors in rats

Background

Long‐term antipsychotic treatment in patients with schizophrenia can induce supersensitivity psychosis and tardive dyskinesia which is thought to be caused by dopamine D₂ receptor sensitization. We evaluated the effects of brexpiprazole on D₂ receptor sensitivity after subchronic treatment in rats. We also evaluated whether brexpiprazole could suppress enhanced response to D₂ receptors in rats subchronically dosed with another atypical antipsychotic.

Methods

The maximum D₂ receptor density (B_max) and apomorphine (a D₂ receptor agonist)‐induced stereotypy were measured in rats orally dosed with vehicle, haloperidol (1 mg/kg), or brexpiprazole (4 or 30 mg/kg for B_max, 6 or 30 mg/kg for stereotypy) for 21 days. Then, effects of oral administrations of brexpiprazole (3 mg/kg), aripiprazole (10 mg/kg), and olanzapine (3 mg/kg) against increases in apomorphine‐induced hyperlocomotion and (±)‐2,5‐dimethoxy‐4‐iodoamphetamine hydrochloride (DOI: a 5‐HT_2A receptor agonist)‐induced head twitches were evaluated in rats subcutaneously treated with risperidone (1.5 mg/kg/d) via minipumps for 21 days.

Results

Haloperidol and brexpiprazole (30 mg/kg: approximately tenfold ED₅₀ of anti‐apomorphine‐induced stereotypy) but not brexpiprazole (4 or 6 mg/kg) significantly increased the B_max and apomorphine‐induced stereotypy. Brexpiprazole (3 mg/kg) and olanzapine (3 mg/kg) significantly suppressed both increases in apomorphine‐induced hyperlocomotion and also DOI‐induced head twitches in rats subchronically treated with risperidone, but aripiprazole (10 mg/kg) significantly suppressed only apomorphine‐induced hyperlocomotion.

Conclusion

Brexpiprazole has a low risk of D₂ receptor sensitization after a repeated administration and suppresses the rebound phenomena related to D₂ and 5‐HT_2A receptors after a repeated administration of risperidone.

Brexpiprazole has less potential to evoke dopamine D2 receptor supersensitivity in rats after repeated administration compared to haloperidol. In addition, brexpiprazole may have a lower risk for producing rebound symptoms associated with D2 receptor, 5‐HT2A receptor sensitization when switching from other antipsychotics such as risperidone.

The preclinical profile of brexpiprazole: what is its clinical relevance for the treatment of psychiatric disorders?

Brexpiprazole is a serotonin-dopamine activity modulator in clinical development for schizophrenia, adjunctive treatment of major depressive disorder, agitation in Alzheimer's disease and post-traumatic stress disorder. It is a partial agonist at 5-HT1A and D2 receptors with similar potency, and an antagonist at 5-HT2A and adrenergic α1B/2C receptors. Compared with aripiprazole, brexpiprazole is more potent at 5-HT1A receptors and displays less intrinsic activity at D2 receptors. This unique serotonin and dopamine modulatory activity has shown robust antipsychotic, antidepressant-like and anxiolytic activities, and limited extrapyramidal symptom liability with pro-cognitive efficacy in animal models. Phase III clinical trials have been successfully completed in schizophrenia and adjunctive use in major depressive disorder, with the US FDA approval obtained for these uses; Phase III studies in Alzheimer's disease and post-traumatic stress disorder are ongoing.

Could dietary trans fatty acids induce movement disorders? Effects of exercise and its influence on Na⁺K⁺-ATPase and catalase activity in rat striatum

The influence of trans fatty acids (FA) on development of orofacial dyskinesia (OD) and locomotor activity was evaluated. Rats were fed with diets enriched with 20% soybean oil (SO; n-6 FA), lard (L; saturated FA) or hydrogenated vegetable fat (HVF; trans FA) for 60 weeks. In the last 12 weeks each group was subdivided into sedentary and exercised (swimming). Brains of HVF and L-fed rats incorporated 0.33% and 0.20% of trans FA, respectively, while SO-fed group showed no incorporation of trans FA. HVF increased OD, while exercise exacerbated this in L and HVF-fed rats. HVF and L reduced locomotor activity, and exercise did not modify. Striatal catalase activity was reduced by L and HVF, but exercise increased its activity in the HVF-fed group. Na(+)K(+)-ATPase activity was not modified by dietary FA, however it was increased by exercise in striatum of SO and L-fed rats. We hypothesized that movement disorders elicited by HVF and less by L could be related to increased dopamine levels in striatum, which have been related to chronic trans FA intake. Exercise increased OD possibly by increase of brain dopamine levels, which generates pro-oxidant metabolites. Thus, a long-term intake of trans FA caused a small but significant brain incorporation of trans FA, which favored development of movement disorders. Exercise worsened behavioral outcomes of HVF and L-fed rats and increased Na(+)K(+)-ATPase activity of L and SO-fed rats, indicating its benefits. HVF blunted beneficial effects of exercise, indicating a critical role of trans FA in brain neurochemistry.

Alpha-phenyl-N-tert-butylnitrone prevents oxidative stress in a haloperidol-induced animal model of tardive dyskinesia: investigating the behavioural and biochemical changes

Haloperidol (HP) is a widely prescribed antipsychotic drug used for the treatment of mental disorders. However, while providing therapeutic benefits, this drug also causes serious extrapyramidal side effects, such as tardive dyskinesia (TD). Upon chronic administration, HP causes behavioural supersensitivity to dopamine D2 receptor agonists, as well as the development of vacuous chewing movements (VCMs), in an animal model of human TD. Currently, a prevailing hypothesis to account for these behavioural abnormalities implicates oxidative stress. This study was undertaken to examine whether the free radical trapping agent, α-phenyl-N-tert-butylnitrone (PBN), can prevent the development of behavioural supersensitivity to dopamine D2 receptor agonists and the development of VCMs. Additionally, the study examined whether increased synthesis of apoptosis inducing factor (AIF) can result from HP-induced oxidative stress. Male Sprague-Dawley rats were treated with HP in conjunction with PBN, or its vehicle, for 4weeks. After a 24-hour washout period, behavioural observations were recorded along with the estimation of lipid peroxidation and antioxidant enzyme activities. The free radical trapping agent, PBN, prevented the development of behavioural supersensitivity, reduced lipid peroxidation and prevented the reduction of antioxidant enzyme activities. AIF concentrations at the mRNA and protein levels remained unchanged; therefore increased AIF gene expression is unlikely to be involved in HP-induced oxidative stress. The findings of the present study suggest the involvement of striatal free radicals in the development of behavioural supersensitivity, and free radical trapping agents, such as PBN, as possible options for the treatment of extrapyramidal side effects in humans.

Protective effect of Morus alba leaves on haloperidol-induced orofacial dyskinesia and oxidative stress

Long-term treatment with haloperidol, a typical neuroleptic, induces neurodegeneration caused by excitotoxicity and oxidative stress, which play an important role in the development of orofacial dyskinesia. In the present investigation, an attempt has been made to examine the effect of a concomitant treatment of methanol extract of Morus alba Linn. (Moraceae) leaves (100-300 mg/kg, i.p.) and haloperidol (1 mg/kg, i.p.) on an animal model of tardive dyskinesia. Rats were treated for 21 days with haloperidol and Morus alba extract; vacuous chewing movements and tongue protrusions were counted. The extract attenuated the increase in vacuous chewing movements and tongue protrusions induced by haloperidol, which were quantified on day 22. The extract showed a marked effect on behavioral parameters altered by haloperidol treatment. Similar treatment with extract attenuated haloperidol-induced lipid peroxidation and nitrite and normalized superoxide dismutase, catalase, and protein in comparison to the control group. The results suggest a protective effect of Morus alba extract against haloperidol-induced orofacial dyskinesia and oxidative stress.

Neuroleptic treatment effect on mitochondrial electron transport chain: peripheral blood mononuclear cells analysis in psychotic patients

A limitation in the use of classic neuroleptic drugs is the eventual appearance of extrapyramidal symptoms. Some studies, mainly based on experimental situations, have related these symptoms with a defect in the mitochondrial electron transport chain (ETC), especially with complex I (CI). One of the advantages of the "atypical" neuroleptics is a lower incidence of movement disorders. We studied peripheral blood mononuclear cells from naive schizophrenic patients (n = 25) and patients under chronic treatment with 1 "typical" neuroleptic (haloperidol, n = 15) or 1 "atypical" neuroleptic (risperidone, n = 23; or clozapine, n = 21). Patients were on standard clinical situation, on treatment for at least 28 months, and did not present signs or symptoms of extrapyramidal dysfunction. Absolute enzyme activities of ETC complexes I to IV were spectrophotometrically quantified, and oxygen consumption with substrates of different complexes was measured polarographically. As an indirect measure of oxidative damage, we quantified membrane lipid peroxidation through the loss of cis-parinaric acid fluorescence. We found differences among groups when comparing the activity of CI, which was decreased in patients receiving neuroleptics, either assessed enzymatically or through oxygen consumption. This effect was lower for atypical neuroleptics than for haloperidol. Haloperidol was also associated with a significant increase of peripheral blood mononuclear cell membrane peroxidation. We conclude that antipsychotics given at clinical standard doses, either typical or atypical, inhibit CI of the ETC. It remains to be established if this finding in a nontarget tissue for antipsychotics may account for the lower incidence of movement disorders observed in patients on atypical agents.

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.

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.

Effects of social isolation on aging-induced orofacial movements in rats

World population is becoming older, and aging is a common risk factor for a number of pathologies. In this respect, it is important to study possible factors that could modify alterations implicated in the process of aging. The aim of the present study is to verify the effects of social isolation on the expression of orofacial movements in adult and old rats. Adult and old rats were housed isolated for 5 days or kept in their home cages in groups of six. Before and after this period, orofacial movements and open-field general activity were evaluated. Aging-induced orofacial movements were abolished by isolation. On the other hand, isolated adult rats presented an increase in orofacial movements. General activity was decreased by aging but was not modified by isolation. Our results indicate that social isolation produces different effects in adult and old rats, and these effects are specific for orofacial movements and not related to a decrease in general motor activity.

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.

Electron spin resonance spectroscopy reveals alpha-phenyl-N-tert-butylnitrone spin-traps free radicals in rat striatum and prevents haloperidol-induced vacuous chewing movements in the rat model of human tardive dyskinesia

The typical antipsychotic drug haloperidol causes vacuous chewing movements (VCM) in rats, which are representative of early-Parkinsonian symptoms or later-onset extrapyramidal side effects of tardive dyskinesia (TD) in humans. Haloperidol (HP) has been hypothesized to potentiate increases in oxidative stress or free radical-mediated levels of toxic metabolites in rat striatum while simultaneous upregulating dopamine (DA)-D2 receptors leading to presumed DA supersensitivity. Alpha(alpha)-Phenyl-N-tert-butylnitrone (PBN) is an antioxidant used to combat oxidative stress and measure increases in PBN spin-adduct activity. Thus, the aim of this study was to investigate whether VCMs are related to upregulation of DA-D2 receptors or to increased levels of free radicals produced during oxidative stress, and whether PBN had any protective effects. Rats received daily chronic (28 day) i.p. injections of saline, haloperidol (2 mg/kg), PBN (150 mg/kg), or haloperidol + PBN. The VCM model was used to measure extrapyramidal side effects of drug treatments. Electron spin resonance (ESR) spectroscopy was performed to compare concentrations of free radical species in rats receiving injections of HP + PBN. To examine the upregulation of DA-D2 receptors, binding assays were carried out to assess the increase in DA-D(2) receptor numbers with respect to VCMs following treatment of rats injected with HP, PBN, and HP + PBN. Results of these experiments show that HP-induced VCMs in rats results from increases in oxidative cellular events and may not be related to increases in striatal DA-D(2) receptors.

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.

Important role of striatal catalase in aging- and reserpine-induced oral dyskinesia

Tardive dyskinesia, the most serious iatrogenic movement disorder, has been tentatively associated with nigrostriatal dopaminergic supersensitivity and with oxidative stress. It is also suggested that long-term neuroleptic treatment does not cause oral dyskinesia (OD), but interacts with some substrate of brain aging, resulting in the premature emergence of OD, that can occur spontaneously with aging. In order to investigate a possible role of nigrostriatal dopaminergic supersensitivity and of oxidative stress in aging- and reserpine-induced OD, the stereotyped behavior induced by dopaminergic agonists, a functional index of dopaminergic striatal activity, as well as the striatal antioxidant enzymes glutathione peroxidase and catalase were assessed. We demonstrate that, opposite to normotensive Wistar rats (NWR), spontaneously hypertensive rats (SHR) do not develop aging- or reserpine-OD. There were no differences between NWR and SHR in stereotyped behavior or in striatal glutathione peroxidase activity. Adult and old SHR presented higher striatal catalase activity relative to NWR, and aging increased it only in SHR. The catalase inhibitor aminotriazole reverted the absence of aging- and reserpine-induced OD in SHR. Our results suggest an important role of striatal catalase in the development of reserpine- and aging-induced OD.

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.

Antidyskinetic effects of risperidone on animal models of tardive dyskinesia in mice

The effects of risperidone, an atypical neuroleptic, were investigated on two animal models of tardive dyskinesia (TD). The repeated administration of reserpine (1.0mg/kg) or haloperidol (2.0mg/kg) induces orofacial movements in mice, which are very similar to those observed in humans presenting TD. The effects of acute or repeated treatment with several doses of risperidone (0.1; 0.5; 2.0 or 4.0) on the expression and development of orofacial movements in reserpine- and haloperidol-treated male mice were investigated. The results showed that risperidone per se did not induce the development of orofacial movements. In addition, this drug was able to attenuate the expression and the development of reserpine-as well as haloperidol-induced orofacial movements. These results are in line with several clinical studies that suggest not only a lower incidence of TD in schizophrenic patients treated with risperidone, but also an antidyskinetic effect of this drug in patients previously treated with classical neuroleptics.

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.

Concomitant development of oral dyskinesia and memory deficits in reserpine-treated male and female mice

It has been suggested that reserpine-induced oral dyskinesia in rats may provide a new animal model of tardive dyskinesia. Both cognitive deficits and gender have been associated with the development of tardive dyskinesia. The aim of the present study was to investigate the effects of reserpine administration on the development of orofacial dyskinesia and on plus-maze discriminative avoidance task (DAT-an animal model of associative learning) in male and female mice. Male and female mice received 1.0 mg/kg reserpine or saline subcutaneously on day 1. On days 3, 6 and 8, the frequency of vacuous chewing movements (VCM) was quantified. On day 6, the DAT conditioning was performed, in a modified elevated plus-maze. In one of the enclosed arms, the animals received aversive stimulation (light and noise). On day 8, a test session was performed and the time spent by the animals in each of the enclosed arms was recorded. Our results showed that reserpine-treated male and female mice presented significantly higher VCM when compared with respective control groups in all observation days. On day 6, reserpine-treated female mice presented significantly higher VCM when compared with male mice injected with this drug. The DAT test performed on day 8 showed that the time spent in the aversive arm by saline-treated mice was significantly lower than the time spent in the non-aversive arm. This difference was not observed for reserpine-treated mice. Our results demonstrate the development of reserpine-induced oral dyskinesia in both male and female mice. While this oral dyskinesia is accompanied by a cognitive deficit in both genders, female mice tended to have more severe oral dyskinesia. It is suggested that reserpine-induced oral dyskinesia may provide a quick, simple and efficient mouse model of tardive dyskinesia.

The mitochondrial toxin 3-nitropropionic acid aggravates reserpine-induced oral dyskinesia in rats

The effects of a previous long-term administration of the mitochondrial toxin 3-nitropropionic acid were studied on an animal model of tardive dyskinesia, i.e., the frequency of spontaneous tongue protrusions in rats repeatedly treated with reserpine. 3-Nitropropionic acid (10 or 15 mg/kg i.p., every other day for 17 days) potentiated the increase in tongue-protrusion frequency induced by reserpine (1 mg/kg, s.c., every other day for 3 days) but did not modify reserpine-induced increase in immobility duration and decrease in locomotion frequency. These results support the notion that neurotoxic events are associated with the development of tardive dyskinesia.

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.

Effects of buspirone on an animal model of tardive dyskinesia

1. The effects of buspirone were studied on an animal model of tardive dyskinesia, i.e., the quantification of orofacial dyskinesia in rats repeatedly treated with reserpine. 2. Rats were co-treated with saline [SAL] or buspirone [BUS] (3.0 mg/kg, i.p., twice daily) and vehicle [VEH] or reserpine [RES] (0.1 mg/kg, s.c., once every other day) for 19 days. On the day 20, the animals were observed for quantification of the behavioral parameters of orofacial dyskinesia: tongue protrusion and vacuous chewing movements frequencies and duration of twitching of the facial musculature. 3. Rats of the SAL + RES group exhibited a significant increase in the three behavioral parameters of orofacial dyskinesia relative to the rats of the SAL + VEH group. However, animals of the BUS + RES group showed only an increased frequency of vacuous chewing movements when compared to animals of the SAL + VEH group. In addition, the duration of the facial twitching was significantly decreased in the BUS + RES group in relation to rats of the SAL + RES group. There were no significant differences in the orofacial parameters between the BUS + VEH and the SAL + VEH groups. 4. Because it was also verified that chronic buspirone treatment was able to increase apomorphine-induced yawning behavior, the possibility is raised that buspirone attenuates reserpine-induced orofacial dyskinesia through the development of dopamine autoreceptor supersensitivity.

Intermittency in mastication and apomorphine-induced gnawing

Rhythmic behaviors like mastication, gnawing, and locomotion, are characterized by temporal segmentation or intermittency. That is, they frequently occur as a series of short bursts interrupted by pauses rather than as one long uninterrupted burst. The function of intermittency as well as the mechanisms that produce it are unknown. Biogenic amine systems may play a role in producing intermittency; however, experimental work to confirm this is only in its infancy. The current study evaluates the structure of intermittency associated with mastication and apomorphine-induced gnawing in the guinea pig. Thirteen free-roaming animals were videotaped while masticating or gnawing. Eight animals were given 0.5 mg/kg i.m. apomorphine and videotaped while gnawing. The remaining five animals received no apomorphine injections, but were taped while feeding on alfalfa pellets. Custom software was used to score instances of maximum jaw closures in videotaped mastication and gnawing sequences. The time between successive maximum jaw closures, called the interocclude interval (IOI), was calculated for all scored sequences. A cutoff IOI value of 0.26 s differentiated pauses (IOI values equal or greater than 0.26 s) from chews or gnaws (IOI values less than 0.26 s). Two or more successive chews or gnaws, without intervening pauses, defined behavior bursts. Chew, gnaw, and burst durations were quantified and compared. Chew and gnaw durations were similar. However, chewing bursts were significantly longer than gnawing bursts. The significance of these results is presented in light of previous neurophysiological work on rhythmic jaw movements and intermittency.

Reserpine does not induce orofacial dyskinesia in spontaneously hypertensive rats

The nigrostriatal dopaminergic system seems to be involved in both reserpine-induced orofacial dyskinesia in normal rats and in the pathogenesis of hypertension in spontaneously hypertensive rats. In the present study, repeated reserpine administration (1.0 mg/kg, s.c., every other day, for 3 days) increased tongue protrusion and vacuous chewing frequencies as well as the duration of facial twitching in Wistar normotensive but not in spontaneously hypertensive rats. These results suggest that genetic hypertension and drug-induced orofacial movements may be inversely modulated by similar mechanisms in the nigrostriatal dopaminergic system.

Study on the suitability of a rat model for tardive dyskinesia and the preventive effects of various drugs

1. Male Sprague-Dawley rats (weighing 260-300 g) were administered 1.5 mg/kg of haloperidol (HPD) intraperitoneally once daily for 28 days to produce an animal model for tardive dyskinesia (TD). The daily administration of HPD significantly increased the frequency of involuntary orofacial movements (chewing movements, tongue protrusions and buccal tremors). 2. Its suitability as a model for TD was assessed in terms of the therapeutic effects of 6 drugs [trihexyphenodyl hydrochloride(THP), clonazepam(CZP), sodium valproate(VPA), alpha-tocopherol(Vit E), ritanserin(RS) and propranolol hydrochloride(PPL)]. These drugs were also used concomitantly with HPD to study their preventive effect. 3. As for the therapeutic effects of the drugs, both the single and the 14-day daily administrations of CZP as well as of VPA significantly suppressed the chewing movements. The results were mostly consistent with the effect of each drug on human TD, indicating this would be an excellent model for TD in terms of the drug responsiveness. 4. The concomitant administration of RS from the start of HPD administration significantly suppressed the appearance of chewing movements. The concomitant administration of Vit E for 42 days also suppressed chewing movements and buccal tremors. On the other hand, the concomitant administration of THP tended to aggravate these involuntary movements. 5. The fact that the therapeutic and preventive effects of the drugs on this model differed suggested that the development and recovery of the movements might also differ, at least in part.

Effects of age on a new animal model of tardive dyskinesia

The effects of age were studied on a new animal model of tardive dyskinesia, i.e., the quantification of oral dyskinesia in rats repeatedly treated with reserpine. Adult and old rats received two injections of reserpine (0.5 or 1.0 mg/kg s.c.) or vehicle, separated by 48 h. One, 10, 25 and 40 days after the second injection of reserpine or vehicle, the animals were observed for quantification of the behavioral parameters of oral dyskinesia: tongue protrusion and vacuous chewing movement frequencies and duration of twitching of the facial musculature. Phenomenologically, control old rats and reserpine-treated adult animals showed very similar oral dyskinesia. When compared to control adult rats, the significant increase in tongue protrusion frequency induced by reserpine treatment was more persistent in the old rats than in the adult animals. Because it is well known that age increases the persistence of tardive dyskinesia, our data provide further support for the validation of reserpine-induced oral dyskinesia as an animal model of tardive dyskinesia. In addition, the possibility is raised that a common pathophysiological mechanism may underlie tardive dyskinesia and age- and reserpine-induced oral dyskinesia.

Effects of monosialoganglioside on a new model of tardive dyskinesia

1- The effects of monosialoganglioside GM1 were studied on a new model of tardive dyskinesia, i.e., the frequency of spontaneous tongue protrusions in rats repeatedly treated with reserpine. 2- Rats were co-treated with vehicle (VEH) or reserpine (RES) (0.1 mg/kg, s.c., every other day) and saline (SAL) or GM1 (5 mg/kg, i.p., every day) for 30 days and observed for tongue protrusions on days 10, 20 and 30. 3- During each test day animals of the RES + SAL group exhibited an increase in tongue protrusions relative to rats of the VEH + SAL group. However, rats of the RES + GM1 group showed an increased frequency of tongue protrusions only on day 10, when compared to animals of the VEH + SAL group. There were no significant differences in tongue protrusion frequency between the VEH + GM1 and the VEH + SAL groups. 4- These results differ from previous studies which reported a facilitatory effect of GM1 co-administration on conventional behavioral animal models of tardive dyskinesia. The possibility is raised that GM1 attenuates the reserpine-induced increase in tongue protrusions through its protective effect on glutamate/oxidative stress neurotoxicity.

The subsensitivity of striatal glutamate receptors induced by chronic haloperidol in rats

The aim of the present study was to investigate the influence of chronic treatment with haloperidol on the contralateral head turns and rotations induced by intrastriatal agonists of NMDA and non-NMDA receptors in rats. N-Methyl-D-aspartate (NMDA, 500 ng/0.5 mu l), alpha-amino-3-hydroxy-5-methyl-4-isoxasole-propionic acid (AMPA, 1000 ng/0.5 mu l) or kainic acid (50 ng/0.5 mu l), injected into the intermediate and caudal parts of the caudate-putamen, induced contralateral head turns and rotations. Haloperidol was given to animals in a dose of ca. 1 mg/kg per day in drinking water for 6 weeks. On day 5 of withdrawal, haloperidol decreased the number of contralateral head turns, but did not significantly influence the contralateral rotations induced by NMDA, AMPA and kainic acid. At the same time, haloperidol enhanced the stereotypy induced by apomorphine (0.25 mg/kg s.c.). The present results seem to suggest that, apart from supersensitivity to dopamine, chronic treatment with haloperidol also induces subsensitivity of striatal NMDA and non-NMDA receptors.

GM1 ganglioside attenuates the development of vacuous chewing movements induced by long-term haloperidol treatment of rats

Tardive dyskinesia (TD) is a serious side-effect of long-term treatment with neuroleptics. To investigate if TD may be a result of neuroleptic-induced excessive stimulation of striatal glutamate receptors, the effect of the anti-excitotoxic GM1 ganglioside was studied in a rat model of TD. In an acute experiment each of four groups of rats was treated with GM1 20 mg/kg SC+saline IP, saline SC+haloperidol 1.2 mg/kg IP, GM1 SC+haloperidol IP, or saline SC+saline IP. In a subsequent long-term experiment lasting 16 weeks, each of the four groups was treated as in the acute experiment, with the exception that haloperidol was injected IM as decanoate 38 mg/kg every 4 weeks, and the controls received vehicle injections. The behavior was videotaped and scored at intervals during both experiments, including 16 weeks after cessation of the long-term treatment. Haloperidol induced a significant increase in vacuous chewing movements (VCM) and immobility both in the acute and in the long-term experiment. Other categories of behaviour (rearing, moving, sitting) were significantly affected only in the acute experiment. GM1 did not affect any of the acute behavioural effects of haloperidol, but significantly reduced VCM in the long-term experiment. The effects on VCM of haloperidol and GM1 persisted for at least 8 weeks after cessation of the long-term treatment. These results suggest that long-lasting changes in striatal function induced by excessive glutamate receptor stimulation may be a mechanism for the development of VCM in rats and perhaps also for TD in humans.

Tardive dyskinesia: behavioral effects of repeated intracerebroventricular haloperidol injections in rats do not confirm the kindling hypothesis

The development of tardive dyskinesia (TD) has been claimed to be the result of a kindling-like mechanism. This hypothesis is based on studies suggesting that intermittent neuroleptic treatment may increase the risk of irreversible TD in humans and persistent vacuous chewing movements (VCM) in rats. We investigated the effect of daily intracerebroventricular (ICV) injections of haloperidol 37.5 micrograms/kg for 12 weeks in rats. Behavior was recorded immediately after the first injection, with 2 weeks intervals during treatment, and 3 weeks after drug withdrawal. In a separate experiment, rats received one injection of haloperidol IP. The acute effect of haloperidol ICV was an immediate increase in VCM and a reduction in motor activity that lasted for approximately 2 h. The behavioral response to haloperidol IP was similar, but of much longer duration. No significant behavioral changes were observed either 24 h after the ICV injections during haloperidol treatment or 3 weeks after drug withdrawal. The results did not support the hypothesis that kindling is important for the development of TD.

The relationship between motor effects in rats following acute and chronic haloperidol treatment

Tardive dyskinesia (TD) is a serious and sometimes irreversible side-effect to long-term neuroleptic treatment. In order to find predictors for development of TD, it would be of interest to known whether susceptibility to develop acute side-effects increases the risk of TD development. The study investigated in female Sprague-Dawley rats the relationship between haloperidol-induced acute motor effects, assessed by means of the grid test and the open field test, and the chronic motor effect assessed as vacuous chewing movements (VCM). The doses of haloperidol were 1.2, 2.4 and 4.8 mg/kg IP in the acute experiments and haloperidol decanoate 38 mg/kg per 4 weeks IM in the chronic experiment. The VCM obtained at different timepoints during the 24 weeks of chronic treatment were highly correlated. However, no correlation was found between the motor effects in the acute and the chronic experiments. The study does not indicate any connection between susceptibility to acute side-effects on neuroleptics and later development of TD.

Psychopharmacological properties of calcium channel inhibitors

The previous decade has witnessed a major expansion of knowledge of the role played by voltage-sensitive calcium channels in the function of the central nervous system. Significant progress in the field has been made possible with the broadening use of organic calcium channel inhibitors (CCIs, Ca2+ antagonists), until recently considered almost exclusively as peripherally active antianginal and antiarrhythmic drugs. CCIs, however, do penetrate the blood-brain barrier from the periphery. Autoradiographic studies have established a highly heterogeneous distribution of CCI recognition sites within the brain. The existing evidence suggests that CCIs have marked psychotropic properties. The profile of their central activity is unique and spans a wide range of effects. Nevertheless, question regarding potentially confounding potent peripheral effects of these drugs remain. This paper reviews the psychopharmacology of CCIs, concentrating on preclinical data, but including supportive clinical and biochemical evidence as well. It focuses on these drugs' antidepressant, antidopaminergic (neuroleptic-like), anxiolytic and anticonvulsant effects. CCIs may also modify the reinforcing properties of some addictive drugs.

Diltiazem suppresses quinpirole-induced oral stereotypies in haloperidol withdrawn rats

1. Tardive dyskinesia (TD) is one of the most serious untoward effects of chronic neuroleptic therapy. Dopaminergic receptor sensitization is assumed to be involved in its pathogenesis. 2. Male Wistar rats were administered (b.i.d.) intragastrically haloperidol (2 mg/kg), diltiazem (5 mg/kg), diltiazem plus haloperidol, and water (controls), for 21 days. 3. Forty eight hours after withdrawal the rats were injected ip with 0.3 mg/kg of quinpirole and observed for stereotypic behaviors (rearing, grooming, licking, and tongue protrusions). 4. There was a significant overall between-group difference in the duration of grooming and the number of tongue protrusions. The haloperidol withdrawn rats scored markedly higher than control and diltiazem alone treated rats. 5. Conjoint treatment with diltiazem and haloperidol prevented the increase of tongue protrusion episodes. 6. We conclude that concurrent diltiazem and haloperidol administration can prevent the occurrence of some behavioral manifestations of dopaminergic receptor supersensitivity, including a lingual dyskinesia.

SCH 23390: D-1 modulation of oral dyskinesias induced in snakes by Xenopus skin mucus

The granular gland skin secretion of Xenopus laevis induces seven involuntary oral dyskinesias and climbing behavior in the water snake Nerodia sipedon. In a previous study the D-2 receptor antagonist, haloperidol (HAL), selectively potentiated mucus-induced yawning and chewing but attenuated fixed gaping; other oral behaviors were unaffected; HAL alone induced no dyskinesias and failed to modify mucus-induced decreases in tongue flicking, cage climbing and activity. As skin compounds have neuroleptic properties known to induce human and animal dyskinesias, we hypothesized that D-1 receptor antagonism may modulate the four of seven mucus-induced dyskinesias and the climbing not altered by HAL. We found that, like HAL, SCH 23390 (SCH) potentiated mucus-induced yawning, attenuated fixed gaping and had no effect on climbing. Unlike HAL's potentiation of chewing, SCH attenuated chewing and potentiated writhing tongue movements. SCH alone, like skin mucus, attenuated tongue flicking and activity but, given with mucus, SCH increased tongue flicking and activity to control levels. Compared to the HAL study, results suggest that mucus-induced yawning and fixed gaping are similarly modulated by both HAL and SCH, while these drugs have opposite effects on writhing tongue and chewing. SCH given alone or with frog mucus had unique effects on activity and normal tongue flicking.