Effects of valproic acid on an animal model of tardive dyskinesia

A Focused Update on Tardive Dyskinesia

Tardive dyskinesia (TD) is a delayed and potentially irreversible motor complication following chronic exposure to centrally acting dopamine receptor antagonists, mainly of the class of antipsychotics drugs. New generations of antipsychotic drugs reduced its mean prevalence to 20%, but it continues to mar the drug experience and social integration in a significant fraction of patients. The underlying molecular cascade remains elusive, explaining in part why TD management is so often difficult. Protocol variations between experimental laboratories and inter-species differences in the biological response to antipsychotic drugs have added layers of complexity. The traditional dopamine D2 receptor supersensitivity hypothesis was revisited in an experimental nonhuman primate model. Findings in the striatum revealed a strong upregulation of D3, not D2, receptors specific to dyskinetic animals, and indirect evidence suggestive of a link between overactivation of glycogen synthase kinase-3β signaling and TD. New effective vesicular monoamine transporter type 2 inhibitors alleviating TD have been approved in the USA. They were integrated to an emerging stepwise treatment algorithm for troublesome TD, which also includes consideration for changes in the current antipsychotic drug regimen and recognition of potentially aggravating factors such as anticholinergic co-medications. These advances may benefit TD.

Personalized and precision medicine as informants for treatment management of bipolar disorder

DSM-5 diagnostic categories, defined by a set of psychopathological symptoms are heterogeneous conditions that may include different biological entities, with distinct etiopathogenesis, different courses and requiring different treatment management. For bipolar disorder the major evidences for this lack of validity are the long paths before a proper diagnosis, the inconsistence of treatment guidelines, the long phases of pharmacological adjustment and the low average of long-term treatment response rates. Personalized medicine for mental disorders aims to couple established clinical-pathological indexes with new molecular profiling to create diagnostic, prognostic and therapeutic strategies precisely tailored to each patient. Regarding bipolar disorder, the clinical history and presentation are still the most reliable markers in stratifying patients and guiding therapeutic management, despite the research goes to great lengths to develop new neuropsychological or biological markers that can reliably predict individual therapy effectiveness. We provide an overview of the advancements in personalized medicine in bipolar disorder, with particular attention to how psychopathology, age at onset, comorbidity, course and staging, genetic and epigenetic, imaging and biomarkers can influence treatment management and provide an integration to the conventional treatment guidelines. This approach may offer a new and rational path for the development of treatments for targeted subgroups of patients with bipolar disorder.

Antiepileptic drugs in non-epilepsy disorders: relations between mechanisms of action and clinical efficacy

Antiepileptic drugs (AEDs) are used extensively to treat multiple non-epilepsy disorders, both in neurology and psychiatry. This article provides a review of the clinical efficacy of AEDs in non-epilepsy disorders based on recently published preclinical and clinical studies, and attempts to relate this efficacy to the mechanism of action of AEDs and pathophysiological processes associated with the disorders. Some newer indications for AEDs have been established, while others are under investigation. The disorders where AEDs have been demonstrated to be of clinical importance include neurological disorders, such as essential tremor, neuropathic pain and migraine, and psychiatric disorders, including anxiety, schizophrenia and bipolar disorder. Many of the AEDs have various targets of action in the synapse and have several proposed relevant mechanisms of action in epilepsy and in other disorders. Pathophysiological processes disturb neuronal excitability by modulating ion channels, receptors and intracellular signalling pathways, and these are targets for the pharmacological action of various AEDs. Attention is focused on the glutamatergic and GABAergic synapses. In psychiatric conditions such as schizophrenia and bipolar disorder, AEDs such as valproate, carbamazepine and lamotrigine appear to have clear roles based on their effect on intracellular pathways. On the other hand, some AEDs, e.g. topiramate, have efficacy for nonpsychiatric disorders including migraine, possibly by enhancing GABAergic and reducing glutamatergic neurotransmission. AEDs that seem to enhance GABAergic neurotransmission, e.g. tiagabine, valproate, gabapentin and possibly levetiracetam, may have a role in treating neurological disorders such as essential tremor, or anxiety disorders. AEDs with effects on voltage-gated sodium or calcium channels may be advantageous in treating neuropathic pain, e.g. gabapentin, pregabalin, carbamazepine, oxcarbazepine, lamotrigine and valproate. Co-morbid conditions associated with epilepsy, such as mood disorders and migraine, may often respond to treatment with AEDs. Other possible disorders where AEDs may be of clinical importance include cancer, HIV infection, drug and alcohol abuse, and also in neuroprotection. A future challenge is to evaluate the second-generation AEDs in non-epilepsy disorders and to design clinical trials to study their effects in such disorders in paediatric patients. Differentiation between the main mechanisms of action of the AEDs needs more consideration in drug selection for tailored treatment of the various non-epilepsy disorders.

Progesterone attenuates neuroleptic-induced orofacial dyskinesia via the activity of its metabolite, allopregnanolone, a positive GABA(A) modulating neurosteroid

GABAergic hypofunction in the basal ganglia is stated as an important mechanism underlying the pathophysiology of tardive dyskinesia. In the present study we sought to establish the protective effect of progesterone in haloperidol-induced orofacial dyskinesia. Besides this we also tried to find out whether the GABA(A) facilitatory action of progesterone metabolites is responsible for the action of progesterone in attenuating the haloperidol-induced orofacial dyskinesia, an animal model of tardive dyskinesia. Chronic administration of haloperidol (1 mg/kg, i.p. 21 days) induced significant increase in hyperkinetic orofacial dyskinetic movements and oxidative damage in the brain as compared to control group. Coadministration of progesterone (5-20 mg/kg, i.p. 21 days) dose dependently prevented the hyperkinetic orofacial movements as well as oxidative damage parameters. The protective activity of progesterone was reversed by pre treatment with finasteride (50 mg/kg i.p.), a 5alpha-reductase inhibitor that blocks the metabolism of progesterone to allopregnanolone and other metabolites. Further, chronic administration of haloperidol resulted in significant decrease in dopamine levels in rat striatum homogenates and increase in catecholamine metabolite levels. Coadministration of progesterone also reversed the decrease in dopamine levels induced by chronic haloperidol treatment, an effect which was again reversed by pre treatment with finasteride. Our study provides strong evidence that the protective effect of progesterone resides in the GABAergic as well as neuroprotective activity of its metabolite allopregnanolone. These findings lend support to recognized GABA hypofunction theory of tardive dyskinesia and strongly suggest progesterone as a protective therapy in this debilitating movement disorder.

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.

Association of Serotonin 2A Receptor and Lack of Association of CYP1A2 Gene Polymorphism with Tardive Dyskinesia in a Turkish Population

The aim of this study was to investigate the possible association of serotonin 2A receptor gene (HTR2A) -1438 G/A polymorphism and CYP1A2 gene 163C/A polymorphism with tardive dyskinesia (TD) in a Turkish population. A total of 47 patients with persistent TD, 80 patients who were consistently without TD, and 100 healthy controls were included in this study. The polymorphic regions of -1438 G/A polymorphism of HTR2A receptor gene (rs6311) and 163C/A of CYP1A2 (rs762551) gene were amplified using polymerase chain reaction (PCR), followed by digestion with restriction enzymes MspI and Bsp1201. Genotype and allele frequencies were calculated by the chi(2)-test. Crude and adjusted odds ratios (ORs) were estimated, and 95% confidence intervals (CIs) were computed by multivariate logistic regression analysis. The genotype and allele frequencies of HTR2A and CYP1A2 gene were similar in schizophrenia with TD, schizophrenia without TD, and healthy controls. The logistic regression analysis showed that cumulative exposure to antipsychotic drugs for every year (p = 0.003; OR = 1.15; CI = 1.07-1.23), and AA genotype of HTR2A gene (p = 0.0258; OR = 4.34; CI = 1.19-15.81) are risk factors for TD. The same logistic regression model showed no association between CYP1A2 polymorphism and TD. The results of the present study seem to indicate that HTR2A gene polymorphism influences the tendency to express TD following prolonged antipsychotic drug exposure in Turkish schizophrenia patients.

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.

A blessing in disguise: Resolution of tardive dyskinesia with development of cervical myelitis

Tardive dyskinesia (TD), which is frequently seen in patients treated with dopamine receptor blocking agents, is difficult to manage. We report on a young Chinese man with bipolar disorder who developed TD after haloperidol treatment, involving the trunk, limbs, and orofacial area. TD persisted despite switching to atypical antipsychotic agents and treatment with valproate, benzodiazepines, and tetrabenazine. Resolution only occurred years later when he developed quadriplegia arising from infective myelitis of the cervical cord (C4-5). He had concomitant vertebral osteomyelitis, which was successfully treated with intravenous antibiotics. With intensive rehabilitation, he recovered the use of his limbs, but had no recurrence of TD. We attribute the resolution of orofacial dyskinesias with a cervical lesion to the interconnections between the orofacial area and cervical spine via the trigeminal nucleus (which has fibers descending as far caudally as C6), as well as to resetting of cortical maps.

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.

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.

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.

Valproic Acid:

Clinical pharmacologists, neurologists, and all health care givers must consider the efficacy, safety, and side effect profile of a given antiepileptic drug when determining which drug is best for a given patient.The purpose of this study was to investigate valproic acid with a detailed analysis of the different reports.