Valproate and carbamazepine increase prefrontal dopamine release by 5-HT1A receptor activation

Priapism associated with anti-seizure medications: a pharmacovigilance study and a review of published cases

BACKGROUND

Recently, case reports of priapism associated with the use of some anti-seizure medications began to emerge in the literature. We aimed to investigate if there is a potential safety signal of priapism among individual anti-seizure medications and to search the literature for relevant published cases.

RESEARCH DESIGN AND METHODS

We conducted a disproportionality analysis using OpenVigil 2.1 to query the United States Food and Drug Administration's Adverse Event Reporting System (FAERS) database. Literature search was conducted in PubMed/MEDLINE, Scopus and Web of Science up to 12 July 2023.

RESULTS

We identified positive signal of priapism for valproic acid and its derivatives (n = 23, chi-squared = 59.943, PRR = 4.566), gabapentin (n = 20, chi-squared = 9.790, PRR = 2.060), lamotrigine (n = 16, chi-squared = 8.318, PRR = 2.120), levetiracetam (n = 16, chi-squared = 10.766, PRR = 2.329), topiramate (n = 14, chi-squared = 28.067, PRR = 3.972) and carbamazepine (n = 8, chi-squared = 6.147, PRR = 2.568), as well as published cases of priapism associated with these drugs. We also found published cases of priapism for pregabalin and phenytoin in the literature and FAERS, and at least one reported adverse event of priapism in FAERS for clonazepam, lacosamide, ethosuximide, oxcarbazepine, and vigabatrin in which they were considered primary suspect.

CONCLUSIONS

Our study identified signals for priapism for several anti-seizure medications, but these results need to be confirmed in well-designed pharmacoepidemiological studies.

Genetics and antiepileptic mood stabilizer treatment response in bipolar disorder: what do we know?

Antiepileptic mood stabilizers (AED-MS) are often used to treat bipolar disorder (BD). Similar to other mood disorder medications, AED-MS treatment response varies between patients. Identification of biomarkers associated with treatment response may ultimately help with the delivery of individualized treatment and lead to improved treatment efficacy. Here, we conducted a narrative review of the current knowledge of the pharmacogenomics of AED-MS (valproic acid, lamotrigine and carbamazepine) treatment response in BD, including genetic contributions to AED-MS pharmacokinetics. Genes involved in neurotransmitter systems and drug transport have been shown to be associated with AED-MS treatment response. As more studies are conducted, and experimental and analytical methods advance, knowledge of AED-MS pharmacogenomics is expected to grow and contribute to precision medicine in BD.

Serotonin/dopamine interaction: Electrophysiological and neurochemical evidence

The interaction between serotonin (5-HT) and dopamine (DA) in the central nervous system (CNS) plays an important role in the adaptive properties of living animals to their environment. These are two modulatory, divergent systems shaping and regulating in a widespread manner the activity of neurobiological networks and their interaction. The concept of one interaction linking these two systems is rather elusive when looking at the mechanisms triggered by these two systems across the CNS. The great variety of their interacting mechanisms is in part due to the diversity of their neuronal origin, the density of their fibers in a given CNS region, the distinct expression of their numerous receptors in the CNS, the heterogeneity of their intracellular signaling pathway that depend on the cellular type expressing their receptors, and the state of activity of neurobiological networks, conditioning the outcome of their mutual influences. Thus, originally conceptualized as inhibition of 5-HT on DA neuron activity and DA neurotransmission, this interaction is nowadays considered as a multifaceted, mutual influence of these two systems in the regulation of CNS functions. These new ways of understanding this interaction are of utmost importance to envision the consequences of their dysfunctions underlined in several CNS diseases. It is also essential to conceive the mechanism of action of psychotropic drugs directly acting on their function including antipsychotic, antidepressant, antiparkinsonian, and drug of abuse together with the development of therapeutic strategies of Alzheimer's diseases, epilepsy, obsessional compulsive disorders. The 5-HT/DA interaction has a long history from the serendipitous discovery of antidepressants and antipsychotics to the future, rationalized treatments of CNS disorders.

Assessment of the biomarkers of hepatotoxicity following carbamazepine, levetiracetam, and carbamazepine-levetiracetam adjunctive treatment in male Wistar rats

Objective

This study examined some of the biomarkers of hepatotoxicity following chronic treatment with carbamazepine (CBZ), levetiracetam (LEV), and CBZ + LEV adjunctive treatment in male rats.

Method

Twenty-four male Wistar rats (140-150 g) were randomized into four groups (n = 6) to receive oral dose of normal saline (0.1 mL), CBZ (25 mg/kg), LEV (50 mg/kg) or sub-therapeutic dose of CBZ (12.5 mg/kg) together with LEV (25 mg/kg) for 28 days. Activities of the liver enzymes and oxidative stress markers were determined while liver histomorphology was also carried out. Data were analyzed using descriptive and inferential statistics. The results were presented as mean ± SEM in graphs or tables, while the level of significance was taken at p < 0.05.

Results

The activities of alkaline-phosphatase and malondialdehyde concentrations increased significantly in all the drug treatment groups, while the activities of superoxide dismutase decreased significantly following CBZ, and CBZ + LEV treatment. Alanine-aminotransferase activities increased significantly in the CBZ and CBZ + LEV treated rats compared with control. The liver section of CBZ treated rats showed mild vascular congestion.

Conclusion

None of these AEDs treatment is devoid of hepatotoxicity. However, the adverse effects in CBZ were greater than LEV, or CBZ + LEV adjunctive treatment.

Valproic Acid-Induced Liver Injury: A Case-Control Study from a Prospective Pharmacovigilance Program in a Tertiary Hospital

Introduction: Valproic acid (VPA) is an antiepileptic drug extensively used for treating partial and generalised seizures, acute mania and as prophylaxis for bipolar disorder. Drug-induced liver injury (DILI) persists as a significant issue related to fatal outcomes by VPA. The aim of this study was to increase our knowledge about this condition and to better identify patients affected. Methods: We conducted an observational retrospective case-control study that identified cases of DILI by VPA from the Pharmacovigilance Programme from our Laboratory Signals at La Paz University Hospital from January 2007 to December 2019. From the Therapeutic VPA Monitoring program, two control groups were assigned, VPA-tolerant patients and the other with patients who developed mild VPA-related liver injury but who did not meet the DILI criteria, matched for date, age and sex. Results: A total of 60 patients were included in the study: 15 cases of DILI, 30 VPA-tolerant controls and 15 controls with mild liver injury. Mean age for the cases was 45.7 years, 4 (26.7%) were women and 5 (33.34%) were children under 18 years, of them 3 (20%) were fatal. Polytherapy with other antiepileptic drugs (p = 0.047) and alcohol consumption (p < 0.001) were associated with a greater risk of developing DILI by VPA. A diagnosis of epileptic seizure was more frequently related to DILI when compared with the VPA-tolerant controls (p < 0.001). The cases developed hepatocellular liver injury (p < 0.001), while the mild hepatic damage controls had a higher rate of cholestatic liver injury (p < 0.001). The laboratory lactate dehydrogenase values were statistically higher (even at baseline) in patients with DILI than in both control groups (p = 0.033 and p = 0.039). Conclusions: VPA hepatotoxicity remains a considerable problem. This study offers interesting findings for characterising VPA-induced liver injury and at-risk patients.

Valproic Acid for the Management of Agitation and Delirium in the Intensive Care Setting: A Retrospective Analysis

PURPOSE

Valproic acid has been proposed as an alternative agent for treatment of agitation and delirium in the intensive care unit (ICU). Clinical data to support the use of valproic acid for this indication are limited. The objective of this analysis was to assess the efficacy and safety associated with the use of valproic acid for the management of agitation and delirium in the ICU.

METHODS

This retrospective descriptive analysis included patients who were prescribed valproic acid for a minimum of 3 days for the treatment of agitation and/or delirium in the cardiac, surgical, or medical ICU from May 31, 2015 to December 31, 2017. The prevalence of agitation and delirium was assessed during valproic acid therapy for up to 7 days. Additional data analyzed included opioid, sedative, and antipsychotic requirements and safety outcomes.

FINDINGS

A total of 47 patients met the inclusion criteria. There was an observed downward trend in the prevalence of agitation (47.8% vs 16.7%) and delirium (84.8% vs. 63.3%) throughout valproic acid therapy. In addition, the proportion of patients who required dexmedetomidine, benzodiazepines, antipsychotics, and opioids decreased while patients were taking valproic acid. No adverse effects attributed to valproic acid occurred in this patient population.

IMPLICATIONS

Valproic acid may be an alternative option to assist in the management of agitation and delirium in the ICU. Additional prospective data are needed to validate the use of this agent for the treatment of agitation and delirium in critically ill patients.

Valproic Acid and Epilepsy: From Molecular Mechanisms to Clinical Evidences

After more than a century from its discovery, valproic acid (VPA) still represents one of the most efficient antiepi-leptic drugs (AEDs). Pre and post-synaptic effects of VPA depend on a very broad spectrum of actions, including the regu-lation of ionic currents and the facilitation of GABAergic over glutamatergic transmission. As a result, VPA indirectly mod-ulates neurotransmitter release and strengthens the threshold for seizure activity. However, even though participating to the anticonvulsant action, such mechanisms seem to have minor impact on epileptogenesis. Nonetheless, VPA has been reported to exert anti-epileptogenic effects. Epigenetic mechanisms, including histone deacetylases (HDACs), BDNF and GDNF modulation are pivotal to orientate neurons toward a neuroprotective status and promote dendritic spines organization. From such broad spectrum of actions comes constantly enlarging indications for VPA. It represents a drug of choice in child and adult with epilepsy, with either general or focal seizures, and is a consistent and safe IV option in generalized convulsive sta-tus epilepticus. Moreover, since VPA modulates DNA transcription through HDACs, recent evidences point to its use as an anti-nociceptive in migraine prophylaxis, and, even more interestingly, as a positive modulator of chemotherapy in cancer treatment. Furthermore, VPA-induced neuroprotection is under investigation for benefit in stroke and traumatic brain injury. Hence, VPA has still got its place in epilepsy, and yet deserves attention for its use far beyond neurological diseases. In this review, we aim to highlight, with a translational intent, the molecular basis and the clinical indications of VPA.

The anxiolytic effects of cannabidiol in chronically stressed mice are mediated by the endocannabinoid system: Role of neurogenesis and dendritic remodeling

Repeated injections of cannabidiol (CBD), the major non-psychotomimetic compound present in the Cannabis sativa plant, attenuate the anxiogenic effects induced by Chronic Unpredictable Stress (CUS). The specific mechanisms remain to be fully understood but seem to involve adult hippocampal neurogenesis and recruitment of endocannabinoids. Here we investigated for the first time if the behavioral and pro-neurogenic effects of CBD administered concomitant the CUS procedure (14 days) are mediated by CB₁, CB₂ or 5HT_1A receptors, as well as CBD effects on dendritic remodeling and on intracellular/synaptic signaling (fatty acid amide hydrolase - FAAH, Akt, GSK3β and the synaptic proteins Synapsin Ia/b, mGluR1 and PSD95). After 14 days, CBD injections (30 mg/kg) induced anxiolytic responses in stressed animals in the elevated plus-maze and novelty suppressed feeding tests, that were blocked by pre-treatment with a CB₁ (AM251, 0.3 mg/kg) or CB₂ (AM630, 0.3 mg/kg), but not by a 5HT_1A (WAY100635, 0.05 mg/kg) receptor antagonist. Golgi staining and immunofluorescence revealed that these effects were associated with an increase in hippocampal neurogenesis and spine density in the dentate gyrus of the hippocampus. AM251 and AM630 abolished the effects of CBD on spines density. However, AM630 was more effective in attenuating the pro-neurogenic effects of CBD. CBD decreased FAAH and increased p-GSK3β expression in stressed animals, which was also attenuated by AM630. These results indicate that CBD prevents the behavioral effects caused by CUS probably due to a facilitation of endocannabinoid neurotransmission and consequent CB₁/CB₂ receptors activation, which could recruit intracellular/synaptic proteins involved in neurogenesis and dendritic remodeling.

Serotonergic modulation of the activity of mesencephalic dopaminergic systems: Therapeutic implications

Since their discovery in the mammalian brain, it has been apparent that serotonin (5-HT) and dopamine (DA) interactions play a key role in normal and abnormal behavior. Therefore, disclosure of this interaction could reveal important insights into the pathogenesis of various neuropsychiatric diseases including schizophrenia, depression and drug addiction or neurological conditions such as Parkinson's disease and Tourette's syndrome. Unfortunately, this interaction remains difficult to study for many reasons, including the rich and widespread innervations of 5-HT and DA in the brain, the plethora of 5-HT receptors and the release of co-transmitters by 5-HT and DA neurons. The purpose of this review is to present electrophysiological and biochemical data showing that endogenous 5-HT and pharmacological 5-HT ligands modify the mesencephalic DA systems' activity. 5-HT receptors may control DA neuron activity in a state-dependent and region-dependent manner. 5-HT controls the activity of DA neurons in a phasic and excitatory manner, except for the control exerted by 5-HT_2C receptors which appears to also be tonically and/or constitutively inhibitory. The functional interaction between the two monoamines will also be discussed in view of the mechanism of action of antidepressants, antipsychotics, anti-Parkinsonians and drugs of abuse.

Valproic Acid for Treatment of Hyperactive or Mixed Delirium: Rationale and Literature Review

BACKGROUND

Delirium is the most often encountered psychiatric diagnosis in the general hospital, with an incidence of up to 82% in the intensive care unit setting and with significant detrimental effects on patients' morbidity and mortality. Antipsychotics are often considered the first-line pharmacological treatment of delirium, but their use may be limited by lack of efficacy, existing contraindications (e.g., prolonged QTc intervals), or resulting side effects (e.g., akathisia). Valproic acid (VPA) is a potential alternative or adjunct treatment. It has multiple mechanisms of action, including effects on neurotransmitter modulation, neuroinflammation, oxidative stress, and transcription, all of which are implicated in the pathophysiology of delirium. Yet, data on the use of this agent in delirium are limited.

OBJECTIVE/METHODS

In this article, we discuss postulated mechanisms of VPA action that provide a theoretical basis for its use in the treatment of hyperactive and mixed type delirium, based on the known and theorized pathophysiology of delirium. We also discuss potential side effects and considerations with use of VPA.

CONCLUSIONS

VPA has multiple modulatory effects on neurotransmitter systems, inflammation, oxidative stress, and transcriptional changes implicated in pathophysiology of delirium. When carefully chosen, VPA can be an effective and well-tolerated treatment option for the management of hyperactive and mixed type delirium. Randomized controlled trials are needed to establish tolerability and efficacy of VPA for treatment of delirium.

Auditory working memory predicts individual differences in absolute pitch learning

Absolute pitch (AP) is typically defined as the ability to label an isolated tone as a musical note in the absence of a reference tone. At first glance the acquisition of AP note categories seems like a perceptual learning task, since individuals must assign a category label to a stimulus based on a single perceptual dimension (pitch) while ignoring other perceptual dimensions (e.g., loudness, octave, instrument). AP, however, is rarely discussed in terms of domain-general perceptual learning mechanisms. This is because AP is typically assumed to depend on a critical period of development, in which early exposure to pitches and musical labels is thought to be necessary for the development of AP precluding the possibility of adult acquisition of AP. Despite this view of AP, several previous studies have found evidence that absolute pitch category learning is, to an extent, trainable in a post-critical period adult population, even if the performance typically achieved by this population is below the performance of a "true" AP possessor. The current studies attempt to understand the individual differences in learning to categorize notes using absolute pitch cues by testing a specific prediction regarding cognitive capacity related to categorization - to what extent does an individual's general auditory working memory capacity (WMC) predict the success of absolute pitch category acquisition. Since WMC has been shown to predict performance on a wide variety of other perceptual and category learning tasks, we predict that individuals with higher WMC should be better at learning absolute pitch note categories than individuals with lower WMC. Across two studies, we demonstrate that auditory WMC predicts the efficacy of learning absolute pitch note categories. These results suggest that a higher general auditory WMC might underlie the formation of absolute pitch categories for post-critical period adults. Implications for understanding the mechanisms that underlie the phenomenon of AP are also discussed.

Is autism a disease of the cerebellum? An integration of clinical and pre-clinical research

Autism spectrum disorders are a group of neurodevelopmental disorders characterized by deficits in social skills and communication, stereotyped and repetitive behavior, and a range of deficits in cognitive function. While the etiology of autism is unknown, current research indicates that abnormalities of the cerebellum, now believed to be involved in cognitive function and the prefrontal cortex (PFC), are associated with autism. The current paper proposes that impaired cerebello-cortical circuitry could, at least in part, underlie autistic symptoms. The use of animal models that allow for manipulation of genetic and environmental influences are an effective means of elucidating both distal and proximal etiological factors in autism and their potential impact on cerebello-cortical circuitry. Some existing rodent models of autism, as well as some models not previously applied to the study of the disorder, display cerebellar and behavioral abnormalities that parallel those commonly seen in autistic patients. The novel findings produced from research utilizing rodent models could provide a better understanding of the neurochemical and behavioral impact of changes in cerebello-cortical circuitry in autism.

Effects of mood stabilizers on marble-burying behavior in mice: involvement of GABAergic system

RATIONALE

Obsessive-compulsive disorder (OCD) is characterized by recurrent unwanted thoughts (obsessions), usually accompanied by repetitive behaviors (compulsions) intended to alleviate anxiety. Marble-burying behavior is a pharmacological model for study of OCD.

OBJECTIVES

In the present study, we examined the effects of mood stabilizers on marble-burying behavior in mice, as well as the role of GABA receptors in this behavior.

METHODS

The effects of treatment with valproate, carbamazepine, lithium carbonate, lamotrigine, muscimol and baclofen on marble-burying behavior in mice were evaluated.

RESULTS

Valproate (10, 30 and 100 mg/kg, i.p.) and carbamazepine (30 and 100 mg/kg, p.o.) significantly reduced marble-burying behavior without affecting total locomotor activity in ICR mice. Lamotrigine (30 mg/kg, i.p.) also significantly reduced marble-burying behavior in ddY mice. On the other hand, lithium carbonate (10, 30 and 100 mg/kg, i.p.) reduced total locomotor activity without affecting marble-burying behavior in ddY mice. The selective GABA(A) receptor agonist muscimol (1 mg/kg) significantly reduced marble-burying behavior without affecting total locomotor activity, whereas the selective GABA(B) receptor agonist baclofen (3 mg/kg) reduced total locomotor activity without affecting marble-burying behavior. Moreover, the selective GABA(A) receptor antagonist bicuculline (3 mg/kg) significantly counteracted the decrease in marble-burying induced by the administration of muscimol (1 mg/kg) and valproate (100 mg/kg).

CONCLUSIONS

These results suggest that GABAergic mechanism is involved in marble-burying behavior, and that valproate, carbamazepine and lamotrigine reduce marble-burying behavior. Moreover, valproate reduces marble-burying behavior via a GABA(A) receptor-dependent mechanism.

Lithium, but not valproic acid or carbamazepine, suppresses impulsive-like action in rats

RATIONALE

Higher impulsivity is a pathological symptom in several psychiatric disorders, including bipolar disorder, and is a risk factor for suicide.

OBJECTIVES

Our goal was to determine whether major mood-stabilizing drugs used for the treatment of bipolar disorder could suppress impulsive-like action in the three-choice serial reaction time task (3-CSRTT).

METHODS

Following training for the 3-CSRTT, rats were acutely administered lithium chloride (LiCl; 0, 3.2, 10, and 32 mg/kg, i.p.), valproic acid (0, 10, 32, and 100 mg/kg, i.p.), or carbamazepine (0, 10, 20, and 30 mg/kg, i.p.). To assess the anorexic effects of lithium, a simple food consumption test was conducted.

RESULTS

LiCl dose-dependently decreased the number of premature responses, an index of impulsive-like action. A high dose of LiCl (32 mg/kg) decreased food consumption, but its anorexic effects were not correlated with the effects of LiCl on premature responses. A moderate dose of LiCl (20 mg/kg) significantly reduced the number of premature responses without affecting motivation-related measures in the 3-CSRTT or the amount of food consumption. Although carbamazepine prolonged reward latency, an index of motivation for food, neither valproic acid nor carbamazepine significantly affected premature responses.

CONCLUSION

It is likely that lithium has a suppressive effect on impulsive action independent of the anorexic effect. Lithium may suppress impulsive behavior and thereby decrease the risk of suicide. The present results could provide an explanation for the antisuicidal effects of lithium and suggest that lithium could be a beneficial treatment for impulsivity-related disorders.

Effects of adjunct valproic acid on clinical symptoms and saccadic eye movements in schizophrenia

OBJECTIVE

Valproic acid (VPA) has been suggested as a potential adjunct therapy in schizophrenia for the treatment of clinical symptoms and cognitive deficits. Here, we investigate the effects of VPA on clinical symptoms and saccadic eye movements while controlling for multiple medication effects.

METHODS

Remitted and first-episode schizophrenia patients taking haloperidol were given adjunct VPA for approximately 2 weeks and tested using a measure of clinical symptoms (Positive and Negative Syndrome Scale) and saccadic eye movement tasks over three testing periods. The effects of VPA were compared with schizophrenia patients medicated with equivalent doses of haloperidol alone (HAL group) and normal controls.

RESULTS

Schizophrenia patients had higher error rates on the antisaccade task (AS task) compared with normal controls. Adjunct VPA did not affect AS task error rates but was associated with an increase in response times for both saccade and AS tasks, with a significantly greater and dose-dependent increase in response times for the AS task. There were no differences in clinical improvement between VPA and HAL schizophrenia patient groups when controlling for haloperidol medication state.

CONCLUSIONS

These results suggest that adjuvant VPA therapy results in both sensorimotor and cognitive slowing but does not either help or further impair inhibitory control in schizophrenia, as measured by the elevated AS task errors.

Clinical and imaging features of Othello's syndrome

BACKGROUND AND PURPOSE

Our objective was to document the clinical and imaging features of Othello's syndrome (delusional jealousy).

METHODS

The study design was a retrospective case series of 105 patients with Othello's syndrome that were identified using the Electronic Medical Record system of Mayo Clinic.

RESULTS

The average age at onset of Othello's syndrome was 68 (25-94) years with 61.9% of patients being male. Othello's syndrome was most commonly associated with a neurological disorder (73/105) compared with psychiatric disorders (32/105). Of the patients with a neurological disorder, 76.7% had a neurodegenerative disorder. Seven of eight patients with a structural lesion associated with Othello's syndrome had right frontal lobe pathology. Voxel-based morphometry showed greater gray matter loss predominantly in the dorsolateral frontal lobes in the neurodegenerative patients with Othello's compared to matched patients with neurodegenerative disorders without Othello's syndrome. Treatment success was notable for patients with dopamine agonist induced Othello's syndrome in which all six patients had improvement in symptoms following decrease in medication.

CONCLUSIONS

This study demonstrates that Othello's syndrome occurs most frequently with neurological disorders. This delusion appears to be associated with dysfunction of the frontal lobes, especially the right frontal lobe.

The acute and chronic effects of combined antipsychotic-mood stabilizing treatment on the expression of cortical and striatal postsynaptic density genes

The detection of changes in postsynaptic gene expression after the administration of mood stabilizers, alone or in combination with antipsychotics, and antidepressants in animal models of drug treatment, may represent a valuable strategy to explore the molecular targets of the mainstay treatments for bipolar disorder. In this study we investigated, in both acute and chronic paradigms, the expression of specific postsynaptic density genes (Homer1a, Homer1b/c, and PSD95) and genes putatively implicated in mood stabilizers mechanism of action (GSK3b, ERK) after administration of first (haloperidol) or second generation antipsychotics (quetiapine 30 mg/kg), alone or in combination with valproate. Moreover, we compared the effects of an antidepressant agent widely used in bipolar depression (citalopram) with a low dose of quetiapine (15 mg/kg), which has been demonstrated to display antidepressant action in bipolar depression. In striatal regions, Homer1a expression was strongly induced by haloperidol compared to all the other treatments. Haloperidol plus valproate also markedly induced Homer1a, but to a significant lesser extent than haloperidol alone. Also in the chronic paradigm haloperidol, but not haloperidol plus valproate, induced Homer1a expression in all the subregions of the caudate-putamen and in the nucleus accumbens core. The high dose of quetiapine significantly induced Homer1a in anterior cingulated, premotor and motor subregions of the cortex, and the extent of induction was significantly higher as compared to the lower dose. Oppositely, Homer1a expression was decreased in the cortex by citalopram acute administration. ERK gene was upregulated in cortex and striatum by the acute treatment with valproate and with the combination of haloperidol or quetiapine plus valproate, whereas no significant differences were noticed in GSK3b expression among treatments. PSD95 showed a significant upregulation by acute citalopram and by haloperidol plus valproate in both cortical and subcortical regions. Haloperidol and quetiapine 30 mg/kg, oppositely, significantly reduced the expression of the gene in the cortex. In conclusion, these results suggest that the combined treatment with a typical or an atypical antipsychotic plus valproate may induce differential modulation of postsynaptic genes expression when compared to the effects of these drugs individually administered.

Role of serotonin in central dopamine dysfunction

The interaction between serotonin (5-HT) and dopamine (DA)-containing neurons in the brain is a research topic that has raised the interest of many scientists working in the field of neuroscience since the first demonstration of the presence of monoamine-containing neurons in the mid 1960. The bulk of neuroanatomical data available clearly indicate that DA-containing neurons in the brain receive a prominent innervation from serotonin (5-hydroxytryptamine, 5-HT) originating in the raphe nuclei of the brainstem. Compelling electrophysiological and neurochemical data show that 5-HT can exert complex effects on the activity of midbrain DA neurons mediated by its various receptor subtypes. The main control seems to be inhibitory, this effect being more marked in the mesocorticolimbic DA system as compared to the DA nigrostriatal system. In spite of a direct effect of 5-HT by its receptors located on DA cells, 5-HT can modulate their activity indirectly, modifying gamma-aminobutyric (GABA)-ergic and glutamatergic input to the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). Although 5-HT/DA interaction in the brain has been extensively studied, much work remains to be done to clarify this issue. The recent development of subtype-selective ligands for 5-HT receptors will not only allow a detailed understanding of this interaction but also will lead to the development of new treatment strategies, appropriate for those neuropsychiatric disorders in which an alteration of the 5-HT/DA balance is supposed.

Chronic psychotropic drug treatment causes differential expression of Reelin signaling system in frontal cortex of rats

Disruption of the Reelin and GABAergic signaling systems have been observed in psychiatric disorders including autism, schizophrenia, bipolar disorder, and major depression. Less is known of therapeutic interventions that may help ameliorate the effects of these disruptions. The current study investigated whether chronic administration of psychotropic medications (clozapine, fluoxetine, haloperidol, lithium, olanzapine, and valproic acid) used in the treatment of psychiatric disorders alters levels of Reelin, its receptor Vldlr, downstream molecules Gsk3 beta, Dab-1, and Gad65/67 in rat prefrontal cortex as measured by qRT-PCR and SDS-PAGE and western blotting. qRT-PCR revealed that mRNAs for Reelin, Vldlr, Dab-1, Gsk3 beta, and Gad65 were each significantly altered by at least one of the drugs tested, and in the case of Reelin, Dab-1, and Gsk3 beta, by multiple drugs. To verify our results, we also performed SDS-PAGE and western blotting experiments. Again, several of the protein products for Reelin, Vldlr, Dab-1, Gsk3 beta, Gad65, and Gad67 were also significantly altered by multiple drugs. The present results suggest that the Reelin signaling and GABAergic systems are affected by commonly used psychotropic medications. These changes may help explain the efficacy of these drugs and provide further support for the investigation of the Reelin and GABAergic signaling systems as therapeutic targets for the treatment of neuropsychiatric diseases.

Effects of mood stabilizers on brain reward processes in rats: studies using the intracranial self-stimulation paradigm

Bipolar disorder is characterized by dysregulated motivation and increased hedonistic drive. d-Amphetamine induces manic symptoms in humans and exacerbates mania in bipolar disorder patients, effects that are counteracted by mood stabilizers. We utilized intracranial self-stimulation (ICSS) to examine how lithium (LiCl), valproate (VPA) or their combination that is commonly used in the clinic affect brain reward function in rats, and how these drugs affect d-amphetamine's reward-facilitating effects. Acute intraperitoneal (i.p.) administration of LiCl (100, 200 mg/kg), VPA (400 mg/kg) or combined administration of subthreshold doses of LiCl (50 mg/kg) and VPA (200 mg/kg) increased ICSS thresholds. LiCl (100 mg/kg) and combined administration of LiCl and VPA (50 and 200 mg/kg), but not VPA alone (200, 400 mg/kg), attenuated d-amphetamine's reward-facilitating effects. These results suggest that ICSS combined with d-amphetamine constitutes a useful model to explore the elation and increased hedonistic drive observed in bipolar patients and ultimately help to identify novel pharmacotherapies for bipolar disorder.

Zonisamide prevents olanzapine-associated hyperphagia, weight gain, and elevated blood glucose in rats

Olanzapine (OLZ), one of the second-generation atypical antipsychotics (SGAs), has shown relative advantages in patient adherence and outcomes. However, OLZ has also been associated with a higher incidence of weight gain than most other SGAs. Excessive weight gain may in turn contribute to long-term health concerns for some individuals. Zonisamide (ZNS), a medication approved in the United States as an adjunct in the management of epilepsy, has a diverse pharmacological profile, including sodium channel blockade, monoamine enhancement, and inhibition of carbonic anhydrase. ZNS has also been reported to cause weight loss in both humans and rodents. We hypothesized that this profile might be beneficial when co-administered with OLZ. To test this hypothesis, we evaluated the effects of OLZ on body weight, as well as the pathways known to regulate feeding behavior and arousal in the Sprague-Dawley rat. As indicated via c-Fos expression, we found an OLZ-induced activation in the nucleus accumbens and orexin neurons in the lateral hypothalamus. An OLZ-associated development of hyperphagia, weight gain and elevated blood glucose in the rat was also found. These outcomes were attenuated and reversed in the presence of concomitant ZNS. These results suggest the hypothesis that ZNS may effectively treat or prevent weight gain or metabolic changes associated with the SGAs. Future studies of this combination in patients through appropriately designed human clinical studies are encouraged.

Valproic acid regulates catecholaminergic pathways by concentration-dependent threshold effects on TH mRNA synthesis and degradation

The spectrum of neurological conditions and psychiatric disorders affected by valproic acid (VPA) ranges from control of seizure and mood disorders to migraine, neuropathic pain, and even congenital malformations and autism. While widely used clinically, the mechanism(s) of action of VPA is not completely understood. Emerging evidence indicates that brain noradrenergic systems contribute to the symptoms of mood disorders and may involve regulation of tyrosine hydroxylase (TH) expression, the rate-limiting enzyme in the biosynthesis of dopamine, norepinephrine and epinephrine. We previously showed that the structurally related short chain fatty acid sodium butyrate (SB) induces TH transcription and alters TH mRNA stability in PC12 cells. The present study was undertaken to determine whether the branched short chain fatty acid VPA could also regulate TH gene expression in vitro. Similar to SB, VPA induced TH transcription at all concentrations tested. VPA-stimulated transcription was significantly attenuated by introducing point mutations in either the canonical cAMP- or in the butyrate-response elements of the TH promoter; or by co-expression of dominant-negative forms of CREB. As with SB, increasing concentrations of VPA demonstrated opposing effects on TH mRNA and protein abundance: elevation of both at low (0.1 mM) but attenuation at concentrations higher than 0.5 mM. This concentration-dependence is consistent with a novel and previously unrecognized cellular/molecular drug regulatory step at the level of TH mRNA stability. Thus, the therapeutic efficacy of VPA might be related to its ability to regulate TH mRNA and protein levels, and thereby central catecholaminergic-dependent behavioral pathways.

Effects of mood stabilizers on the inhibition of adenylate cyclase via dopamine D(2)-like receptors

OBJECTIVE

The mood stabilizing drugs lithium, carbamazepine and valproate modulate brain adenosine monophosphate (cAMP) levels, which are assumed to be elevated in bipolar disorder patients. The aim of this work was to investigate how these three mood stabilizing agents affect the regulation of cAMP levels by dopamine D(2)-like receptors in vitro in rat cortical neurons in culture and in vivo in the rat prefrontal cortex.

METHODS

The production of cAMP was measured in the cultured cortical neurons or in microdialysis samples collected from the prefrontal cortex of freely moving rats using the [8-(3)H] and [(125)I] radioimmunoassay kits.

RESULTS

In vitro and in vivo data showed that the treatment with the mood stabilizing drugs had no effect on basal cAMP levels in vitro, but had differential effects in vivo. Direct stimulation of adenylate cyclase (AC) with forskolin increased cAMP levels both in vitro and in vivo, and this effect was significantly inhibited by all three mood stabilizers. Activation of dopamine D(2)-like receptors with quinpirole partially inhibited forskolin-induced increase in cAMP in untreated cultures, but no effect was observed in cortical neuron cultures treated with the mood stabilizing drugs. Similar results were obtained by chronic treatment with lithium and valproate in the prefrontal cortex in vivo. However, surprisingly, in carbamazepine-treated rats the activation of dopamine D(2)-like receptors enhanced the responsiveness of AC to subsequent activation by forskolin, possibly as a consequence of chronic inhibition of the activity of the enzyme.

CONCLUSIONS

It was shown that each of these drugs affects basal- and forskolin-evoked cAMP levels in a distinct way, resulting in differential responses to dopamine D(2)-like receptors activation.

Nefopam is more potent than carbamazepine for neuroprotection against veratridine in vitro and has anticonvulsant properties against both electrical and chemical stimulation

Nefopam (NEF) is a known analgesic that has recently been shown to be effective in controlling both neuropathic pain and convulsions in rodents. In this study we compared nefopam to carbamazepine (CBZ), a reference antiepileptic drug (AED), for their ability to protect cerebellar neuronal cultures from neurodegeneration induced by veratridine (VTD). Furthermore, we tested nefopam for protection against both, maximal electroshock-induced seizures (MES), and isoniazid-induced seizures in mice. Both NEF and CBZ were effective in preventing both signs of excitotoxicity and neurodegeneration following exposure of cultures to 5 microM veratridine for 30 min and 24 h, respectively. Concentrations providing full neuroprotection were 500 microM CBZ and 50 microM NEF, while the concentration providing 50% neuroprotection was 200 microM for CBZ and 20 microM for NEF. Neither NEF nor CBZ reduced excitotoxicity following direct exposure of cultures to glutamate, but CBZ failed to reduce increases in intracellular calcium following stimulation of L-type voltage sensitive calcium channels. In vivo, NEF (20 mg/kg i.p.) significantly reduced MES and fully prevented MES-induced terminal clonus (TC). In comparison, NEF was significantly more effective than CBZ in preventing MES, although both drugs were equally effective against MES-induced TC. Furthermore, nefopam provided protection against isoniazid-induced seizures at doses similar to those protecting against MES.

Effects of divalproex and atypical antipsychotic drugs on dopamine and acetylcholine efflux in rat hippocampus and prefrontal cortex

Mood stabilizers (e.g., valproic acid) and antipsychotic drugs (APDs) are commonly co-administered in the treatment of bipolar disorder and schizophrenia. The basis for any synergism between these classes of drugs in either group of disorders has been little studied. Previous studies have shown that atypical APDs (e.g., clozapine) preferentially increases dopamine (DA) and acetylcholine (ACh) efflux in rat medial prefrontal cortex (mPFC) and hippocampus (HIP), both of which have been suggested to contribute to their ability to improve cognition in patients with schizophrenia. We have recently reported that the anticonvulsant mood stabilizers (AMS), valproic acid, carbamazepine, and zonisamide, but not lithium, also preferentially increase DA efflux in the rat mPFC, and that, at subthreshold doses, the AMS also augment the ability of the atypical APDs clozapine and risperidone to increase DA but not ACh efflux in the mPFC. The present study examined the ability of divalproex (DVX), which is chemically related to valproic acid, to enhance DA and ACh efflux in the HIP and to augment the effect of atypical APDs on ACh efflux in the HIP and mPFC. DVX, 500 mg/kg, significantly increased DA and ACh efflux in the HIP, and DA, but not ACh, efflux in the mPFC, whereas a lower dose of DVX, 50 mg/kg, had no effect on DA or ACh in either region. However, DVX, 50 mg/kg, combined with the atypical APDs olanzapine (1.0 mg/kg) or aripiprazole (0.3 mg/kg) significantly potentiated the effect of both APDs on DA, but not ACh efflux in the HIP and mPFC. Pretreatment of olanzapine or aripiprazole with the selective serotonin 5-HT(1A) antagonist, WAY100635 (1.0 mg/kg) partially but significantly blocked the effect of the combination of DVX, 50 mg/kg, and olanzapine or aripiprazole, on DA efflux in both the HIP and mPFC. WAY100635 did not affect the ability of the combination of olanzapine or aripiprazole and DVX to enhance ACh efflux in the HIP or mPFC. Subchronic administration of the combination of DVX, 50 mg/kg, and risperidone, produced significantly greater increases in DA and ACh efflux in the mPFC, but these increases were not significantly different from those following the acute administration of the combination of risperidone and DVX. These results provide further evidence that the AMS, DVX, augments the ability of atypical APDs to increase DA or ACh efflux in either the HIP or mPFC or both. The clinical significance of this potentiation for the beneficial clinical effects of this combination of agents and the differences between AMS in this regard warrants further study.

The interaction between dopamine D2-like and beta-adrenergic receptors in the prefrontal cortex is altered by mood-stabilizing agents

Several studies have suggested the involvement of biogenic monoaminergic neurotransmission in bipolar disorder and in the therapy for this disease. In this study, the effects of the mood-stabilizing drugs lithium, carbamazepine or valproate on the dopaminergic and adrenergic systems, particularly on D2-like and beta-adrenergic receptors, were studied both in cultured rat cortical neurones and in rat prefrontal cortex. In vitro and in vivo data showed that stimulation of beta-adrenergic receptors with isoproterenol increased cyclic adenosine monophosphate (cAMP) levels and this effect was significantly inhibited by lithium, carbamazepine or valproate. The activation of dopamine D2-like receptors with quinpirole decreased the isoproterenol-induced rise in cAMP in control conditions. This inhibition was observed in vivo after chronic treatment of the rats with carbamazepine or valproate, but not after treatment with lithium or in cultured rat cortical neurones after 48 h exposure to the three mood stabilizers. Dopamine D2 and beta1-adrenergic receptors were found to be co-localized in prefrontal cortical cells, as determined by immunohistochemistry, but western blot experiments revealed that receptor levels were differentially affected by treatment with the three mood stabilizers. These data show that mood stabilizers affect D2 receptor-mediated regulation of beta-adrenergic signalling and that each drug acts by a unique mechanism.

The Effect of Antiepileptic Drugs on 5-HT1A-Receptor Binding Measured by Positron Emission Tomography

PURPOSE

To study the effect of antiepileptic drugs (AEDs) on 5-HT(1A)-receptor binding in patients with temporal lobe epilepsy. 5-HT(1A)-receptor binding, measured by positron emission tomography, is reduced in patients with temporal lobe epilepsy. Antiepileptic drugs may act on the serotonergic system, as shown in animal models, and thus affect receptor-binding measurements.

METHODS

We analyzed the effect of AEDs on 5-HT(1A)-receptor binding in 31 patients and 10 normal controls. Patients with structural lesions, progressive neurologic disorders, or taking other medications were excluded. None had a seizure for >or=2 days before positron emission tomography (PET). [(18)F]FCWAY PET was performed on a GE Advance scanner with continuous EEG monitoring. Functional images of the distribution volume (V) were generated. Anatomic regions of interest were applied to co-registered PET images, after correction for partial-volume effect.

RESULTS

Patients had significantly higher [(18)F]FCWAY free fraction (f(1)) than did controls. No AED effects were observed on interictal [(18)F]FCWAY binding after correction for plasma free fraction. [(18)F]FCWAY V/f1 reduction in epileptic foci was not affected by AEDs.

CONCLUSIONS

5-HT(1A)-receptor binding is reduced in temporal lobe epileptic foci after partial-volume correction. AED plasma free fractions should be measured when PET receptor studies are performed in patients with epilepsy.

Lithium differs from anticonvulsant mood stabilizers in prefrontal cortical and accumbal dopamine release: role of 5-HT(1A) receptor agonism

Anticonvulsant mood stabilizers, e.g., valproic acid and carbamazepine, and atypical antipsychotic drugs (APDs), e.g., clozapine, quetiapine, olanzapine, risperidone, and ziprasidone, have been reported to preferentially increase dopamine (DA) release in rat medial prefrontal cortex (mPFC), an effect partially or fully inhibited by WAY100635, a selective 5-HT(1A) antagonist. These atypical APDs have themselves been reported to be effective mood stabilizers, although the importance of increased cortical DA release to mood stabilization has not been established. The purpose of the present study was to determine whether zonisamide, another anticonvulsant mood stabilizer, as well as lithium, a mood stabilizer without anticonvulsant properties, also increases prefrontal cortical DA release and, if so, whether this release is also inhibited by 5-HT(1A) antagonism. As with valproic acid and carbamazepine, zonisamide (12.5 and 25 mg/kg) increased DA release in the mPFC, but not the NAC, an increase abolished by WAY100635 (0.2 mg/kg). However, lithium (100 and 250 mg/kg) decreased DA release in the NAC, an effect also attenuated by WAY100635 (0.2 mg/kg). Lithium itself had no effect in the mPFC but the combination of WAY100635 (0.2 mg/kg) and lithium (100 and 250 mg/kg) markedly increased DA release in the mPFC. Furthermore, M100907 (0.1 mg/kg), a selective 5-HT(2A) antagonist, abolished this increase in DA release in the mPFC. These results indicate that not all mood-stabilizing agents but only those, which have anticonvulsant mood-stabilizing properties, increase DA release in the cortex, and that the effect is dependent upon 5-HT(1A) receptor stimulation. However, the combination of lithium and 5-HT(1A) blockade may result in excessive 5-HT(2A) receptor stimulation, relative to 5-HT(1A) receptor stimulation, both of which can increase prefrontal cortical DA release.

Valproic acid potentiates both typical and atypical antipsychotic-induced prefrontal cortical dopamine release

Antipsychotic drugs (APD)s and anticonvulsant mood-stabilizers are now frequently used in combination with one another in treating both schizophrenia and bipolar disorder. We have recently reported that the atypical APDs, e.g. clozapine and risperidone, as well as the anticonvulsant mood-stabilizers, valproic acid (VPA), zonisamide, and carbamazepine, but not the typical APD haloperidol, increase dopamine (DA) release in rat medial prefrontal cortex (mPFC). The increased DA release was partially (atypical APDs) or completely (mood-stabilizers) blocked by the serotonin (5-HT)1A receptor antagonist WAY100635. Diminished prefrontal cortical DA activity may contribute to cognitive impairment in virtually all the patients with schizophrenia and, perhaps, bipolar disorder. Thus, the enhanced release of cortical DA by these agents may be beneficial in this regard. It is, therefore, of considerable interest to determine whether combined administration of these agents augments prefrontal cortical DA release, and if so, whether the increase is dependent upon 5-HT1A receptor activation. VPA (50 mg/kg), which was insufficient by itself to increase prefrontal cortical DA release, potentiated the ability of clozapine (20 mg/kg) and risperidone (1 mg/kg) to increase DA release in the mPFC, but not in the nucleus accumbens (NAC). VPA (50 mg/kg) also potentiated haloperidol (0.5 mg/kg)-induced DA release in the mPFC; this increase was completely abolished by WAY100635 (0.2 mg/kg). These results suggest that, in combination with VPA, both typical and atypical APDs produce greater increases in prefrontal cortical DA release than either type of drug alone via a mechanism dependent upon 5-HT(1A) receptor activation. Furthermore, they provide a strong rationale for testing for possible clinical synergism of an APD and anticonvulsant mood-stabilizer in improving the cognitive deficits present in patients with schizophrenia and bipolar disorder.

Reduction of affective lability and alcohol use following traumatic brain injury: a clinical pilot study of anti-convulsant medications

OBJECTIVE

A large and under-recognized sub-set of patients suffer both traumatic brain injury (TBI) and alcohol dependence (ADep). This group appears to use alcohol to self-treat affective and anxiety lability following TBI, resulting in new ADep or worsened prior ADep. This study hypothesized that treatment of such patients with mood-stabilizing medications would relieve post-TBI emotional dysregulation and facilitate reduction in alcohol use.

DESIGN

This study reported retrospective medical record data from outpatients in the Substance Abuse Treatment Programme who were treated for labile mood. Medications followed clinical indication and were given in non-blind fashion.

METHOD

Subjects included 18 patients who (1) complained of debilitating affective lability following TBI, (2) described drinking alcohol to ease lability symptoms, (3) met DSM-IV criteria for current ADep and (4) were treated with a mood stabilizing medication.

RESULTS

During 6 weeks of treatment, 16 (89%) achieved abstinence from alcohol. All but two (14/16 or 88%) also showed improvement in their affective and anxiety symptoms.

CONCLUSIONS

These preliminary data are limited by the retrospective collection, clinical impression and non-blinded trial. Nonetheless, the results suggest further investigation of anti-convulsants as potentially useful agents in co-morbid emotional lability and ADep following TBI.

Lamotrigine, carbamazepine and phenytoin differentially alter extracellular levels of 5-hydroxytryptamine, dopamine and amino acids

We have studied the effects of treatment with the anticonvulsants lamotrigine (LTG), phenytoin (PHN) and carbamazepine (CBZ) on basal and stimulated extracellular aspartate (ASP), glutamate (GLU), taurine (TAU), GABA, 5-hydroxytryptamine (5-HT) and dopamine (DA) in the hippocampus of freely moving rats using microdialysis. All of the drugs investigated have had inhibition of Na(+) channel activity implicated as their principal mechanism of action. Neither LTG (10-20 mg/kg), PHN (20-40 mg/kg) or CBZ (10-20 mg/kg) had an effect on the basal extracellular concentrations of any of the amino acids studied with the exception of glutamate, which was decreased at the highest LTG dose. However, when amino acid transmitter levels were increased with 50 microM veratridine, LTG was found to cause a dose-dependent decrease in dialysate levels of all four amino acids, with the effect being most pronounced for glutamate. In contrast, PHN decreased extracellular aspartate levels but had no effect on evoked-extracellular GLU, TAU or GABA. Somewhat unexpectedly, CBZ did not alter the stimulated increase in the excitatory amino acids, GLU and ASP, but, rather surprisingly for an antiepileptic drug, markedly decreased that of the inhibitory substances TAU and GABA. The three drugs had differing effects on basal extracellular 5-HT and DA. LTG caused a dose-dependent decrease in both, while CBZ and PHN both increased extracellular 5-HT and DA. When extracellular 5-HT and DA was evoked by veratridine LTG had no significant effect on this, while PHN but not CBZ increased stimulated extracellular 5-HT and both PHN and CBZ augmented DA. Thus, the effects of the three drugs studied seemed to depend on whether extracellular transmitter levels are evoked or basal and the particular transmitter in question. This suggests that there are marked differences in the neurochemical mechanisms of antiepileptic drug action of the three compounds studied.

Lithium and valproate attenuate dextroamphetamine-induced changes in brain activation

BACKGROUND

Previous studies have suggested that both lithium and valproate may decrease phosphoinositol second messenger system (PI-cycle) activity. There is also evidence that dextroamphetamine may increase PI cycle activity. It was previously demonstrated that dextroamphetamine administration in volunteers causes a region and task dependent decrease in brain activation in healthy volunteers. The current study assessed the effect of 14 days pretreatment with lithium and valproate on these dextroamphetamine-induced changes in regional brain activity in healthy volunteers.

METHODS

This was a double-blind, placebo-controlled, study in which volunteers received either 1000 mg sodium valproate (n = 12), 900 mg lithium (n = 9) or placebo (n = 12). Functional images were acquired using functional magnetic resonance imaging (fMRI) while subjects performed three cognitive tasks, a word generation paradigm, a spatial attention task and a working memory task. fMRI was carried out both before and after administration of dextroamphetamine (25 mg). Changes in the number of activated pixels and changes in the magnitude of the blood-oxygen-level-dependent (BOLD) signal after dextroamphetamine administration were then determined.

RESULTS

In keeping with previous findings dextroamphetamine administration decreased regional brain activation in all three tasks. Pretreatment with lithium attenuated changes in the word generation paradigm and the spatial attention task, while pretreatment with valproate attenuated the changes in the working memory task.

CONCLUSIONS

These results suggest that both lithium and valproate can significantly attenuate dextroamphetamine-induced changes in brain activity in a task dependent and region specific manner. This is the first human evidence to suggest that both lithium and valproate may have a similar effect on regional brain activation, conceivably via similar effects on PI-cycle activity.

A comparison of anticonvulsants in the treatment of impulsive aggression

This study compared the behavioral effects of 3 anticonvulsants in impulsive aggressive men. In a double-blind, placebo-controlled, parallel groups design, participants were randomly assigned to 1 of 4 6-week treatments: phenytoin (n = 7), carbamazepine (n = 7), valproate (n = 7), or placebo (n = 8). The efficacy measure was the average aggression score, a global severity index from the Overt Aggression Scale (J. M. Silver & S. C. Yudofsky, 1991). Analysis showed a significant reduction in impulsive aggression during all 3 anticonvulsant conditions compared with placebo. However, the treatment effect during carbamazepine administration was slightly delayed compared with phenytoin and valproate. These findings suggest that increased use of anticonvulsants could make a significant impact in the control of impulsive aggression in both mental health and criminal justice settings.

Effects of combined lamotrigine and valproate on basal and stimulated extracellular amino acids and monoamines in the hippocampus of freely moving rats

The antiepileptic drugs sodium valproate (VPA) and lamotrigine (LTG) are increasingly used in combination in patients in whom monotherapy has failed to control seizures. Although these drugs are known to interact pharmacokinetically, several authors have proposed a pharmacodynamic interaction between the two. In order to investigate this we have studied the effects of combined treatment with LTG and VPA on basal and stimulated extracellular aspartate (ASP), glutamate (GLU), taurine (TAU), gamma amino butyric acid (GABA), 5-hydroxytryptamine (5-HT) and dopamine (DA) release in the hippocampus of freely moving rats using microdialysis. Additionally, we measured the possible effect of VPA on LTG in plasma, whole brain and dialysates. Neither LTG (10 mg/kg) nor VPA (300 mg/kg) given alone significantly altered basal levels of ASP, GLU or TAU. When given together, however, the two drugs significantly reduced extracellular ASP and GLU while increasing TAU levels. In the case of GABA, LTG was without effect on basal levels of the transmitter, but these increased following VPA and this persisted with both drugs. When transmitter release was stimulated by 50 muM veratridine, marked increases in the release of all amino acids occurred and this was decreased by LTG in all cases. VPA alone only altered GABA release, increasing it by approximately the same extent as basal GABA. For all of the amino acids studied, however, VPA reversed the decreases in release seen after LTG. VPA and LTG increased and decreased respectively basal 5-HT and DA. When given together the increase in extracellular 5-HT was greatly prolonged, but no effect on DA release was seen. When 5-HT release was evoked by veratridine this was increased by VPA and no other treatment. With DA, however, neither drug alone altered evoked release, but the two combined led to a marked increase. Co-administration of VPA with LTG showed no significant effect of this combination on LTG in any of the three compartments studied indicating that in this case a significant pharmacokinetic contribution to our findings is unlikely, which suggests that there is a probable pharmacodynamic interaction of the two drugs.

Valproate prevents the induction, but not the expression of morphine sensitization in mice

Repetitive exposure to opioids elicits sensitization to its locomotor stimulating effects. Several lines of evidence have shown that the central GABAergic system is involved in behavioral sensitization induced by morphine. Valproate, a clinically widely used anticonvulsant and mood stabilizer, can mainly inhibit gamma-aminobutyric acid (GABA) transaminase and activate glutamic acid decarboxylase, which result in decrease in the degradation and increase in the synthesis of GABA, and then the elevation of extracellular GABA in the central nervous system. However, the effects of valproate on behavioral sensitization to morphine have not been documented. Herein, we investigated the effects of valproate on the induction and the expression of behavioral sensitization to morphine. Mice treated daily for 7 days with 10 mg/kg morphine and challenged with the same dose after 7 days of washout showed increased locomotor activity. Co-administration of valproate (37.5, 75, 150 mg/kg, intraperitoneal (i.p.)), at doses that did not affect the spontaneous activity, 30 min prior to morphine dose-dependently inhibited the induction of morphine sensitization. However, neither single nor multiple administration (37.5, 75, 150 mg/kg x 7 injections) of valproate had any effect on the expression of morphine sensitization once it developed. Our results indicated that GABA plays an important role in the induction, but not in the expression of morphine sensitization in mice.

Effect of acute and chronic lamotrigine on basal and stimulated extracellular 5-hydroxytryptamine and dopamine in the hippocampus of the freely moving rat

1. We have studied the effects of acute and chronic treatment with the anticonvulsant lamotrigine (LTG) on basal and stimulated extracellular 5-hydroxytryptamine (5-HT), dopamine (DA) and their metabolites in the hippocampus of freely moving rats using in vivo microdialysis. 2. Acute LTG (10 and 20 mg kg(-1)) decreased extracellular 5-HT, but had no effect on its metabolite 5-hydroxyindoleacetic acid (5-HIAA). Dialysate DA was also decreased by LTG as were its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). When transmitter release was stimulated by either 50 microm veratridine or 100 mm K(+), marked increases in the release of both transmitters occurred, but LTG was entirely without effect on this. 3. In chronic experiments, rats were dialysed after 2, 4, 7, 14 and 21 days of LTG treatment (5 mg kg(-1), twice daily). During this period a progressively different response to the drug was seen. After 2 days, basal extracellular 5-HT was significantly greater in treated rats than control rats. This effect persisted up to 14 days, but by 21 days 5-HT levels had returned to control values. 5-HIAA levels were unaltered and there was no effect of LTG on veratridine or K(+) stimulated 5-HT release. 4. Similarly, DA concentrations significantly increased after 2-7 days of LTG treatment, but returned and remained at basal values thereafter. During the treatment period LTG had no effect on extracellular DOPAC, but HVA followed a similar pattern to its parent transmitter. As with 5-HT, at no time point did LTG have any effect on stimulated DA release. 5. These neurochemical findings observed in these experiments are considered in relation to the use of LTG in bipolar disorder.

Convergent effects of lithium and valproate on the expression of proteins associated with large dense core vesicles in NGF-differentiated PC12 cells

Lithium and valproate are chemically unrelated compounds that are used to treat manic-depressive illness. Previously, we reported that lithium ions upregulate genes encoding proteins primarily associated with large dense core vesicles (LDCV) in nerve growth factor (NGF)-differentiated PC12 cells, but not in undifferentiated PC12 cells. Moreover, lithium did not alter the expression of proteins associated with small-clear, synaptic-like vesicles (SSV) in these cells. Based on these observations, we investigated whether valproate had actions similar to those of lithium in PC12 cells. Thus, undifferentiated or NGF-differentiated PC12 cells were exposed to lithium (1 mM) or valproate (1 mM) for 48 h. Extracts from these cells were submitted to semiquantitative Northern and Western analyses. In NGF-differentiated cells, both agents increased the expression of proteins associated with LDCV, the vesicular monoamine transporter 1 (VMAT1), and cysteine string protein (CSP). These same treatments did not alter the expression of proteins primarily associated with SSV, the vesicular acetylcholine transporter (VAChT), and synaptophysin (SY). Furthermore, neither drug affected the expression of these proteins in undifferentiated cells. Interestingly, secretion of (3)H-dopamine was increased in cells exhibiting the increase of VMAT1 and csp. Taken together, the convergent effects of these chemically diverse compounds suggest that altered dynamics of LDCV may play a vital role in the biochemical pathway, leading to the relief of the symptoms of manic depression.

Central 5-HT receptor hypersensitivity in migraine without aura

Serotonin has long been implicated as a key neurotransmitter in migraine. There is a dearth of research specifically examining 5-HT1A receptor sensitivity in migraine despite the importance of this receptor in regulating central serotonergic tone. In this study we examined the hypothesis that migraine without aura is associated with hypersensitivity of central 5-HT1A receptors, using a 5-HT1A neuroendocrine challenge drug and comparing serum prolactin responses between a test group with migraine and a matched group of healthy controls. Twelve female subjects fulfilling International Headache Society (IHS) criteria for migraine without aura were evaluated. Following an overnight fast, subjects presented for testing at 9am. An intravenous canula was inserted and serum prolactin was assessed at baseline and every 30 min for 3 h following a single dose of 30 mg oral buspirone, a 5-HT1A-receptor agonist. Subjects were assessed during the first 5 days of the menstrual cycle. No subjects were taking psychotropic medication or migraine prophylactic treatment. Patients with current or previous psychiatric disorder, daily headache or analgesic overuse were excluded. 16 healthy female volunteers matched for age and menstrual status were also evaluated and served as controls. There was no difference in baseline prolactin between groups. There was a significant rise in prolactin following buspirone in both groups. Subjects with migraine had a significantly increased prolactin response to buspirone (delta max) compared to controls (P < 0.001). This study supports the hypothesis that migraine without aura is associated with a relative hypersensitivity of central 5-HT1A receptors. This is of relevance given the role of the 5-HT1A receptor in controlling raphe 5-HT tone and in the possible association between migraine and anxiety and depression.

Basic pharmacology of valproate: a review after 35 years of clinical use for the treatment of epilepsy

Since its first marketing as an antiepileptic drug (AED) 35 years ago in France, valproate has become established worldwide as one of the most widely used AEDs in the treatment of both generalised and partial seizures in adults and children. The broad spectrum of antiepileptic efficacy of valproate is reflected in preclinical in vivo and in vitro models, including a variety of animal models of seizures or epilepsy. There is no single mechanism of action of valproate that can completely account for the numerous effects of the drug on neuronal tissue and its broad clinical activity in epilepsy and other brain diseases. In view of the diverse molecular and cellular events that underlie different seizure types, the combination of several neurochemical and neurophysiological mechanisms in a single drug molecule might explain the broad antiepileptic efficacy of valproate. Furthermore, by acting on diverse regional targets thought to be involved in the generation and propagation of seizures, valproate may antagonise epileptic activity at several steps of its organisation. There is now ample experimental evidence that valproate increases turnover of gamma-aminobutyric acid (GABA) and thereby potentiates GABAergic functions in some specific brain regions thought to be involved in the control of seizure generation and propagation. Furthermore, the effect of valproate on neuronal excitation mediated by the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors might be important for its anticonvulsant effects. Acting to alter the balance of inhibition and excitation through multiple mechanisms is clearly an advantage for valproate and probably contributes to its broad spectrum of clinical effects. Although the GABAergic potentiation and glutamate/NMDA inhibition could be a likely explanation for the anticonvulsant action on focal and generalised convulsive seizures, they do not explain the effect of valproate on nonconvulsive seizures, such as absences. In this respect, the reduction of gamma-hydroxybutyrate (GHB) release reported for valproate could be of interest, because GHB has been suggested to play a critical role in the modulation of absence seizures. Although it is often proposed that blockade of voltage-dependent sodium currents is an important mechanism of antiepileptic action of valproate, the exact role played by this mechanism of action at therapeutically relevant concentrations in the mammalian brain is not clearly elucidated. By the experimental observations summarised in this review, most clinical effects of valproate can be explained, although much remains to be learned at a number of different levels about the mechanisms of action of valproate. In view of the advances in molecular neurobiology and neuroscience, future studies will undoubtedly further our understanding of the mechanisms of action of valproate.

Role of the cholinergic muscarinic system in bipolar disorder and related mechanism of action of antipsychotic agents

The evidence for the involvement of cholinergic muscarinic receptors in mania and depression is reviewed. Small pilot trials with cholinesterase inhibitors and muscarinic agonists suggest that stimulation of muscarinic receptors may produce an antimanic effect, possibly by activation of muscarinic M(4) receptors. It is concluded that it is not likely that currently used mood stabilizers, such as lithium, valproic acid and carbamazepine, work directly through muscarinic receptor mechanisms. Furthermore, the evidence indicates that antipsychotic agents used for mania are working through the common mechanism of antagonism of dopamine D(2) receptors, and interactions with muscarinic receptors do not play a key role. Finally, it is hypothesized that olanzapine has robust antimanic activity, due to blockade of dopamine D(2) receptors and antagonism of other monoaminergic receptors. Olanzapine may normalize mood due to antidepressant-like activities, such as 5-HT(2A) receptor antagonism and increasing cortical norepinephrine and dopamine.

Interaction between carbamazepine, zonisamide and voltage-sensitive Ca2+ channel on acetylcholine release in rat frontal cortex

To clarify the mechanisms of action of antiepileptic drugs (AEDs), carbamazepine (CBZ) and zonisamide (ZNS), on exocytosis mechanisms, the present study determined the concentration-dependent action of CBZ and ZNS, as well as the interaction between these AEDs and voltage-sensitive Ca(2+) channel (VSCC) activity on basal, Ca(2+)- and K(+)-evoked acetylcholine (ACh) release in frontal cortex of freely moving rat using in vivo microdialysis. Perfusion with therapeutic-relevant concentrations of CBZ and ZNS increased basal ACh release, which was regulated by N-type VSCC predominantly and P-type VSCC weakly, whereas supratherapeutic-relevant concentrations of these AEDs reduced this release. The 3.4 mM Ca(2+)-evoked release, which was regulated by N-type VSCC selectively, but not by P-type VSCC, was increased by therapeutic-relevant concentrations of CBZ and ZNS, whereas this release was reduced by supratherapeutic-relevant concentrations of them. The 50 mM K(+)-evoked release, which was regulated by P-type VSCC predominantly and N-type VSCC weakly, was decreased by CBZ and ZNS, in a concentration-dependent manner. These findings indicate that the interplay between enhancement of basal ACh release and reduction of depolarization-related ACh release in the frontal cortex are at least partially involved in a common mechanism of antiepileptic action between CBZ and ZNS.

Mechanisms of action of carbamazepine and its derivatives, oxcarbazepine, BIA 2-093, and BIA 2-024

Carbamazepine (CBZ) has been extensively used in the treatment of epilepsy, as well as in the treatment of neuropathic pain and affective disorders. However, the mechanisms of action of this drug are not completely elucidated and are still a matter of debate. Since CBZ is not very effective in some epileptic patients and may cause several adverse effects, several antiepileptic drugs have been developed by structural variation of CBZ, such as oxcarbazepine (OXC), which is used in the treatment of epilepsy since 1990. (S)-(-)-10-acetoxy-10,11-dihydro-5H-dibenz [b,f]azepine-5-carboxamide (BIA 2-093) and 10,11-dihydro-10-hydroxyimino-5H-dibenz[b,f] azepine-5-carboxamide (BIA 2-024), which were recently developed by BIAL, are new putative antiepileptic drugs, with some improved properties. In this review, we will focus on the mechanisms of action of CBZ and its derivatives, OXC, BIA 2-093 and BIA 2-024. The available data indicate that the anticonvulsant efficacy of these AEDs is mainly due to the inhibition of sodium channel activity.

Influence of the dopamine D2 receptor (DRD2) exon 8 genotype on efficacy of tiapride and clinical outcome of alcohol withdrawal

We tested the hypothesis that allelic variants of the human dopamine D2 receptor E8 genotype are associated with (i) dopamine D2 antagonist tiapride dose in treatment of alcohol withdrawal (n = 50) and (ii) with anxiety and depression in patients during alcoholism detoxification therapy (admission n = 87; discharge n = 50). DRD2 E8 A/A genotype was associated with increased dose of tiapride during a 9-day detoxification therapy and with increased anxiety and depression scores on admission and 2 weeks later. The findings suggest a pharmacogenetic influence of DRD2 E8 genotype on tiapride efficacy in alcohol withdrawal. In an earlier report, DRD2 E8 A/A genotype was associated with reduced responsiveness to the dopamine D2 agonist apomorphine; however, it is not clear whether both findings share the same biological basis. Earlier findings concerning association of DRD2 E8 A/A with increased anxiety and depression are replicated for the first time.

Determination of effects of antiepileptic drugs on SNAREs-mediated hippocampal monoamine release using in vivo microdialysis

1. To elucidate possible mechanisms underlying the effects of carbamazepine (CBZ), valproate (VPA) and zonisamide (ZNS) on neurotransmitter exocytosis, the interaction between these three antiepileptic drugs (AEDs) and botulinum toxins (BoNTs) on basal, Ca(2+)- and K(+)-evoked release of dopamine (DA) and serotonin (5-HT) were determined by microdialysis in the hippocampus of freely moving rats. 2. Basal release of monoamine was decreased by pre-microinjection of the syntaxin inhibitor, BoNT/C, but only weakly affected by the synaptobrevin inhibitor, BoNT/B. Ca(2+)-evoked release was inhibited by BoNT/C selectively. K(+)-evoked release was reduced by BoNT/B predominantly and BoNT/C weakly. 3. Perfusion with low and high concentrations of CBZ and ZNS increased and decreased basal monoamine release, respectively. Perfusion with VPA increased basal 5-HT release concentration-dependently, whereas basal DA release was affected by VPA biphasic concentration-dependently, similar to CBZ and ZNS. This stimulatory action of AEDs on basal release was inhibited by BoNT/C predominantly. 4. Ca(2+)-evoked monoamine release was increased by low concentrations of CBZ, ZNS and VPA, but decreased by high concentrations. These effects of the AEDs on Ca(2+)-evoked release were inhibited by BoNT/C, but not by BoNT/B. 5. K(+)-evoked monoamine release was reduced by AEDs concentration-dependently. The inhibitory effect of these three AEDs on K(+)-evoked release was inhibited by BoNT/B, but not by BoNT/C. 6. These findings suggest that the therapeutic-relevant concentration of CBZ, VPA and ZNS affects exocytosis of DA and 5-HT, the enhancement of syntaxin-mediated monoamine release during resting stage, and the inhibition of synaptobrevin-mediated release during depolarizing stage.