The new generation of GABA enhancers. Potential in the treatment of epilepsy

GABAB Receptor: Structure, Biological Functions, and Therapy for Diseases

Gamma-aminobutyric acid (GABA) B receptors (GABABRs) that acts slowly and maintains the inhibitory tone are versatile regulators in the complex nervous behaviors and their involvement in various neuropsychiatric disorders, such as anxiety, epilepsy, pain, drug addiction, and Alzheimer's disease. Additional study advances have implied the crucial roles of GABABRs in regulating feeding-related behaviors, yet their therapeutic potential in addressing the neuropsychiatric disorders, binge eating, and feeding-related disorders remains underutilized. This general review summarized the physiological structure and functions of GABABR, explored the regulation in various psychiatric disorders, feeding behaviors, binge eating, and metabolism disorders, and fully discussed the potential of targeting GABABRs and its regulator-binding sites for the treatment of different psychiatric disorders, binge eating and even obesity. While agonists that directly bind to GABABR1 have some negative side effects, positive allosteric modulators (PAMs) that bind to GABABR2 demonstrate excellent therapeutic efficacy and tolerability and have better safety and therapeutic indexes. Moreover, phosphorylation sites of downstream GABABRs regulators may be novel therapeutic targets for psychiatric disorders, binge eating, and obesity. Further studies, clinical trials in particular, will be essential for confirming the therapeutic value of PAMs and other agents targeting the GABABR pathways in a clinical setting.

Fabrication of Oro-Dispersible Sodium Valproate-Loaded Nanofibrous Patches for Immediate Epileptic Innervation

Epilepsy is one of the oldest neurological disorders discovered by mankind. This condition is firmly coupled with unprovoked seizures stimulated by irrepressible neuroelectrical blasts. Orally taken valproate family has been employed for prophylactic management; however, oral administration is not applicable for critical scenarios, thus calling for medication routes fulfilling necessities of immediate innervation. In order to address this shortcoming, sodium valproate entrapped in poly(ethylene oxide)/polyvinylpyrrolidone (PEO/PVP) nanofibrous patches was developed with the aim of sublingual drug delivery. Initially, the production process was designed and optimized via the central composite design (CCD). Nanofiber fabrication was accomplished with a novel device by using the pressurized gyration method. Fabricated biomaterials were chemically, spatially, and thermally inspected. The beanless and homogeneous appearance of both virgin and impregnated nanofibrous patches was morphologically demonstrated via scanning electron microscopy. Additionally, adequately oro-dispersed impregnated patches released more than 90% of their drug content in under a minute. Following in vitro cyto-safety assurance acquired through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay on SH-SY5Y neuroblastoma cells, the protective antiepileptic effect of impregnated patches was affirmed in vivo via pentylenetetrazole kindled-induced Mus musculus animal modeling. The parameter of in vivo behavioral evaluation was the Racine scoring system. Moreover, histopathological distinctions detected between different test groups were highlighted via fluorescence staining. Finally, the oxidative stress was determined according to quantitative variations of malondialdehyde, glutathione, superoxide dismutase, and catalase levels. The overall conclusion herein suggests that sodium valproate-loaded PEO/PVP nanofibrous patches strikingly prevented behavioral, structural, and oxidative deteriorations caused by pentylenetetrazole.

Unraveling the neuroprotective effect of perampanel and lacosamide combination in the corneal kindling model for epilepsy in mice

BACKGROUND

Scientific evidence to guide clinicians on the use of different antiseizure drugs in combination therapy is either very limited or lacking. In this study, the impact of lacosamide and perampanel alone and in combination was tested in corneal kindling model in mice, which is a cost-effective mechanism for screening of antiseizure drugs.

METHODS

The impact of lacosamide (5 mg/kg) and perampanel (0.125 mg/kg) alone and their combination was tested in corneal kindling process (3-mA current for 3 s applied twice daily for consecutive 12 days) in male BALB/c mice. Post-kindling, mice were subjected to a battery of behavioral tests assessing anxiety, memory, and depression-like behaviors. Brain tissues were then harvested for analysis of oxidative stress biomarkers.

RESULTS

Our results showed that the combination therapy of lacosamide and perampanel was more effective in reducing seizure progression than monotherapy of these drugs. Animals treated with combination therapy showed significant behavioral improvements, as reduced anxiety and depression were noticed, and their cognitive abilities were notably better compared to animals of all other groups. Moreover, biochemical assays of isolated brains from combination-treated group revealed lesser amount of oxidative stress. In addition, outcomes of dual regime were comparable to the phenytoin in seizure control but showed superior benefits in mitigation of kindling-prompted behavioral dysfunction and oxidative stress.

CONCLUSIONS

This study suggests that the lacosamide and perampanel combination therapy worked noticeably better in halting the corneal kindling process in mice and improved the epilepsy-associated psychiatric disorders that might be due to antioxidant effects of both drugs.

Development towards a novel screening method for nipecotic acid bioisosteres using molecular imprinted polymers (MIPs) as alternative to in vitro cellular uptake assays

Impaired expression of GABA transporters (GATs) is closely related to the pathogenesis of among others Parkinson's disease and epilepsy. As such, lipophilic nipecotic acid analogs have been extensively studied as GAT1-addressing drugs and radioligands but suffer from limited brain uptake due to the zwitterionic properties of the nipecotic acid moiety. Bioisosteric replacement of the carboxylic acid group is a promising strategy to improve the brain uptake, though it requires knowledge on the binding of these isosteres to GAT1. To screen nipecotic acid isosteres for their affinity to GAT1 in a time- and cost-effective manner, this research aims to develop a molecular imprinted polymer (MIP) that mimics the natural binding site of GAT1 and can act as an alternative screening tool to the current radiometric and mass spectrometry cellular-based assays. To this end, a nipecotic acid MIP was created using the electropolymerization of ortho-phenylenediamine (oPD) by cyclic voltammetry (CV). The optimization of the generated receptor layer was achieved by varying the scan rate (50-250 mV/s) and number of CV cycles (5-12), yielding an optimized MIP with an average imprinting factor of 2.6, a linear range of 1-1000 nm, and a theoretical LOD of 0.05 nm, as analyzed by electrical impedance spectroscopy (EIS). Selectivity studies facilitated the investigation of major binding interactions between the MIP and the substrate, building an experimental model that compares characteristics of various analogs. Results from this model indicate that the substrate carboxylic acid group plays a more important role in binding than an amine group, after comparing the binding of cyclohexanecarboxylic acid (average IF of 1.7) and piperidine (average IF of 0.46). The research culminates in a discussion regarding the feasibility of the in vitro model, comparing the synthetic system against the biological performance of GAT1. Thus, evaluating if it is possible to generate a synthetic GAT1 mimic, and if so, provide directions for follow-up research.

Review of pharmacogenetics of antiseizure medications: focusing on genetic variants of mechanistic targets

Antiseizure medications (ASMs) play a central role in seizure management, however, unpredictability in the response to treatment persists, even among patients with similar seizure manifestations and clinical backgrounds. An objective biomarker capable of reliably predicting the response to ASMs would profoundly impact epilepsy treatment. Presently, clinicians rely on a trial-and-error approach when selecting ASMs, a time-consuming process that can result in delays in receiving alternative non-pharmacological therapies such as a ketogenetic diet, epilepsy surgery, and neuromodulation therapies. Pharmacogenetic studies investigating the correlation between ASMs and genetic variants regarding their mechanistic targets offer promise in predicting the response to treatment. Sodium channel subunit genes have been extensively studied along with other ion channels and receptors as targets, however, the results have been conflicting, possibly due to methodological disparities including inconsistent definitions of drug response, variations in ASM combinations, and diversity of genetic variants/genes studied. Nonetheless, these studies underscore the potential effect of genetic variants on the mechanism of ASMs and consequently the prediction of treatment response. Recent advances in sequencing technology have led to the generation of large genetic datasets, which may be able to enhance the predictive accuracy of the response to ASMs.

Tyrosine kinases: multifaceted receptors at the intersection of several neurodegenerative disease-associated processes

Tyrosine kinases (TKs) are catalytic enzymes activated by auto-phosphorylation that function by phosphorylating tyrosine residues on downstream substrates. Tyrosine kinase inhibitors (TKIs) have been heavily exploited as cancer therapeutics, primarily due to their role in autophagy, blood vessel remodeling and inflammation. This suggests tyrosine kinase inhibition as an appealing therapeutic target for exploiting convergent mechanisms across several neurodegenerative disease (NDD) pathologies. The overlapping mechanisms of action between neurodegeneration and cancer suggest that TKIs may play a pivotal role in attenuating neurodegenerative processes, including degradation of misfolded or toxic proteins, reduction of inflammation and prevention of fibrotic events of blood vessels in the brain. In this review, we will discuss the distinct roles that select TKs have been shown to play in various disease-associated processes, as well as identify TKs that have been explored as targets for therapeutic intervention and associated pharmacological agents being investigated as treatments for NDDs.

Population Pharmacokinetics of Topiramate in Patients with Epilepsy Using Nonparametric Modeling

BACKGROUND

Topiramate (TPM) is used for the treatment of various epileptic seizures and the prevention of migraine. This study aimed to develop a population pharmacokinetic model and identify covariates that influence TPM behavior in patients with epilepsy in Kuwait.

METHODS

Data were collected retrospectively from 108 patients (2 years old and above) with epilepsy who were treated with oral TPM and 174 TPM blood samples from 3 hospitals in Kuwait from 2009 to 2016. Data were randomly divided into 2 groups for model development and validation. The population pharmacokinetic model was built using the nonparametric modeling algorithm (Pmetrics). The model was evaluated internally through the visual predictive check method and externally using a new data set.

RESULTS

A 1-compartment model with first-order elimination fitted the data well. Covariates showing a significant effect on the elimination rate constant were renal function and coadministration of carbamazepine (CBZ). The mean estimated clearance was 2.11 L/h; this was 50% higher for patients coadministered with CBZ. Age and sex were essential covariates for the volume of distribution (V). The visual predictive check of the final model could predict the measured concentrations. External validation further confirmed the favorable predictive performance of the model with low bias and imprecision for predicting the concentration in a particular population.

CONCLUSIONS

TPM elimination was increased with CBZ coadministration and was affected by renal function. Meanwhile, age and sex were the main predictors for V. The predictive performance of the final model proved to be valid internally and externally.

I Feel! Therefore, I Am from Pain to Consciousness in DOC Patients

Pain assessment and management in patients with disorders of consciousness (DOC) is a challenging and important aspect of care, with implications for detecting consciousness and promoting recovery. This narrative review explores the role of pain in consciousness, the challenges of pain assessment, pharmacological treatment in DOC, and the implications of pain assessment when detecting changes in consciousness. The review discusses the Nociception Coma Scale and its revised version, which are behavioral scales used to assess pain in DOC patients, and the challenges and controversies surrounding the appropriate pharmacological treatment of pain in these patients. Moreover, we highlight recent evidence suggesting that an accurate pain assessment may predict changes in the level of consciousness in unresponsive wakefulness syndrome/vegetative state patients, underscoring the importance of ongoing pain management in these patients.

Visualizing GABA transporters in vivo: an overview of reported radioligands and future directions

By clearing GABA from the synaptic cleft, GABA transporters (GATs) play an essential role in inhibitory neurotransmission. Consequently, in vivo visualization of GATs can be a valuable diagnostic tool and biomarker for various psychiatric and neurological disorders. Not surprisingly, in recent years several research attempts to develop a radioligand have been conducted, but so far none have led to suitable radioligands that allow imaging of GATs. Here, we provide an overview of the radioligands that were developed with a focus on GAT1, since this is the most abundant transporter and most of the research concerns this GAT subtype. Initially, we focus on the field of GAT1 inhibitors, after which we discuss the development of GAT1 radioligands based on these inhibitors. We hypothesize that the radioligands developed so far have been unsuccessful due to the zwitterionic nature of their nipecotic acid moiety. To overcome this problem, the use of non-classical GAT inhibitors as basis for GAT1 radioligands or the use of carboxylic acid bioisosteres may be considered. As the latter structural modification has already been used in the field of GAT1 inhibitors, this option seems particularly viable and could lead to the development of more successful GAT1 radioligands in the future.

Role of long noncoding RNAs; BDNF-AS and 17A and their relation to GABAergic dysfunction in Egyptian epileptic patients

Epilepsy is a chronic neurological disorder characterized by recurrent unprovoked seizures. Lately, long noncoding RNAs (lncRNAs) have been increasingly appreciated as regulators of epilepsy-related processes, however, their functional role in its pathogenesis is still to be explored. This study investigated the expression levels of lncRNAs; BDNF-AS and 17A in the sera of Egyptian patients with idiopathic generalized and symptomatic focal epilepsy and correlated their levels with brain-derived neurotrophic factor (BDNF), phosphorylated cAMP reaction element -binding protein (p-CREB), gamma- aminobutyric acid (GABA) and glutamate, to underline their related molecular mechanism. A total of 70 epileptic patients were divided into two clinical types, besides 30 healthy controls of matched age and sex. The expression levels of both lncRNAs were markedly upregulated in epileptic groups versus the healthy control group with predominance in the symptomatic focal one. Epileptic patients showed significantly lower levels of BDNF, p-CREB, GABA along with significant increase of glutamate levels and glutamate/ GABA ratio, especially in symptomatic focal versus idiopathic generalized epileptic ones. The obtained data raised the possibility that these lncRNAs might be involved in the pathogenesis of epilepsy via inhibition of GABA/p-CREB/BDNF pathway. The study shed light on the putative role of these lncRNAs in better diagnosis of epilepsy, particularly symptomatic focal epilepsy.

Neuronal and Non-Neuronal GABA in COVID-19: Relevance for Psychiatry

Infection with SARS-CoV-2, the causative agent of the COVID-19 pandemic, originated in China and quickly spread across the globe. Despite tremendous economic and healthcare devastation, research on this virus has contributed to a better understanding of numerous molecular pathways, including those involving γ-aminobutyric acid (GABA), that will positively impact medical science, including neuropsychiatry, in the post-pandemic era. SARS-CoV-2 primarily enters the host cells through the renin–angiotensin system’s component named angiotensin-converting enzyme-2 (ACE-2). Among its many functions, this protein upregulates GABA, protecting not only the central nervous system but also the endothelia, the pancreas, and the gut microbiota. SARS-CoV-2 binding to ACE-2 usurps the neuronal and non-neuronal GABAergic systems, contributing to the high comorbidity of neuropsychiatric illness with gut dysbiosis and endothelial and metabolic dysfunctions. In this perspective article, we take a closer look at the pathology emerging from the viral hijacking of non-neuronal GABA and summarize potential interventions for restoring these systems.

How prevalent and severe is addiction on GABAmimetic drugs in an elderly German general hospital population? Focus on gabapentinoids, benzodiazepines, and z-hypnotic drugs

OBJECTIVE

Gabapentinoids (GPT) are reported to be increasingly misused by opioid- and polydrug-users, but the addictive potential of GPT outside of these populations remains understudied. Investigations comparing GPT abuse and dependence liability to that of other commonly prescribed Central Nervous System-acting medications are therefore warranted. We provide a comparison of GPT-abuse/dependence to that of other GABAmimetics within an elderly population.

DESIGN

DSM-IV-TR-based data (previously prospectively collected by SKID-I-interview) from a random sample of elderly patients admitted to a metropolitan German general hospital were reviewed. The prevalence and severity of GPT, benzodiazepine (BDZ), and z-hypnotic drug (ZD)-abuse and -dependence were compared, stratified also by mono-substance (no concurrent current or previous substance use) and de novo-substance (first)-abuse and -dependence states.

RESULTS

Among 400 patients (75 ± 6.4 years old; 63% females), neither current nor past abuse of BDZ, ZD or GPT, nor other illicit substances was observed. Dependence upon BDZ, ZD or GPT was observed among 55 (13.75%) individuals. The related lifetime/12-month prevalence-rates were: dependence condition (BDZ: 7%/2.45%; ZD: 4.25%/4.25%; GPT: 2.75/2.5%); mono-dependence condition (BDZ: 2.25%/0.75%; ZD: 1%/1%, GPT: 0%/0%); de novo-dependence condition (BDZ: 2.75%/1.75%; ZD: 1%/1%, GPT: 0.5%/0.5%). Opioid analgesic-dependence (N = 43/400) was significantly more frequently linked with BDZ than with GPT (p < 0.01) [Correction added on 29 December 2021, after first online publication: In the sentence 'Opioid analgesic-dependence…', the term 'and ZD' has been deleted]. For all three GABAmimetic classes, most mono- and de novo-dependence states were mild-to-moderate and lasted 2-6 years (median).

CONCLUSION

GABAmimetic-dependence was usually mixed with other substance-dependences. Every third to fourth instance of BDZ- or ZD-dependence was a mono-dependence condition, while a pure GPT-dependence was absent in this elderly (and illicit substance-naïve) population.

Effects of Antiarrhythmic Drugs on Antiepileptic Drug Action-A Critical Review of Experimental Findings

Severe cardiac arrhythmias developing in the course of seizures increase the risk of SUDEP (sudden unexpected death in epilepsy). Hence, epilepsy patients with pre-existing arrhythmias should receive appropriate pharmacotherapy. Concomitant treatment with antiarrhythmic and antiseizure medications creates, however, the possibility of drug–drug interactions. This is due, among other reasons, to a similar mechanism of action. Both groups of drugs inhibit the conduction of electrical impulses in excitable tissues. The aim of this review was the analysis of such interactions in animal seizure models, including the maximal electroshock (MES) test in mice, a widely accepted screening test for antiepileptic drugs.

Orthopedic surgery-induced cognitive dysfunction is mediated by CX3CL1/R1 signaling

Background

Postoperative pain is a common phenomenon after surgery and is closely associated with the development of postoperative cognitive dysfunction (POCD). Persistent pain and systemic inflammation caused by surgery have been suggested as key factors for the development of POCD. Fractalkine (CX3CL1) and its receptor, the CX3C chemokine receptor 1 (CX3CR1), are known to play a key role in pain and inflammation signaling pathways. Recent studies have shown that the regulation of CX3CR1/L1 signaling influences the development of various diseases including neuronal diseases. We determined whether CX3CR1/L1 signaling is a putative therapeutic target for POCD in a mouse model.

Methods

Adult (9–11 weeks) male mice were treated with neutralizing antibody to block CX3CR1/L1 signaling both before and after surgery. Inflammatory and behavioral responses including pain were assessed postoperatively. Also, CX3CR1 mRNA level was assessed. Hippocampal astrocyte activation, Mao B expression, and GABA expression were assessed at 2 days after surgery following neutralizing antibody administration.

Results

The behavioral response indicated cognitive dysfunction and development of pain in the surgery group compared with the control group. Also, increased levels of pro-inflammatory cytokines and CX3CR1 mRNA were observed in the surgery group. In addition, increased levels of GABA and increased Mao B expression were observed in reactive astrocytes in the surgery group; these responses were attenuated by neutralizing antibody administration.

Conclusions

Increased CX3CR1 after surgery is both necessary and sufficient to induce cognitive dysfunction. CX3CR1 could be an important target for therapeutic strategies to prevent the development of POCD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02150-x.

Addressing Pain for a Proper Rehabilitation Process in Patients With Severe Disorders of Consciousness

Consciousness constitutes a fundamental prerequisite in the individual appraisal and experience of pain. In the same way, a person needs to be able to report on pain perception. Patients who suffered a severe brain injury with disorders of consciousness (DOC) represent a spectrum of pathologies affecting patients' capacity to interact with the external world. In these patients, the most relevant aspects in response to pain are physiologic and behavioral. The treatments and management of pain are challenging issues in these patients, arising serious ethical concerns and bringing emotional load among medical staff, caregivers, and relatives. In this review, we report the importance of having a correct pain management in DOC patients, to individuate the best pharmacological treatment that can make the difference in detecting a behavioral response, indicative of a change in the level of consciousness, and in planning a more effective rehabilitative approach.

Effect of aliskiren on the anticonvulsant activity of antiepileptic drugs against 6 Hz-induced psychomotor seizures in mice

Drug-drug interactions should be considered during the pharmacological treatment in patients with epilepsy and coexisting hypertension. Experimental studies in rodents showed that antihypertensive drugs which block the renin-angiotensin system (RAS) are able to decrease seizure severity. The anticonvulsant efficacy of several antiepileptic drugs (AEDs) was enhanced in different seizure models following concomitant treatment with RAS inhibitors. The current study examined the combined treatment with AEDs (carbamazepine, valproate, phenobarbital, clonazepam, ethosuximide, levetiracetam) and aliskiren, the first inhibitor of renin for treating hypertension, in the mouse 6 Hz psychomotor seizure model. The convulsive threshold was not affected by the renin inhibitor up to a dose of 75 mg/kg i.p. However, aliskiren (75 mg/kg) enhanced the anticonvulsant action of valproate reducing its ED₅₀ value from 96.7 to 25.6 mg/kg (P < 0.01). The anticonvulsant potency of other AEDs was unaffected by aliskiren treatment. The combinations of aliskiren with AEDs did not cause adverse effects in mice evaluated in the rota-rod or passive avoidance task. Administration of the renin inhibitor did not significantly alter either plasma or brain concentration of valproate. The obtained results confirm earlier findings from other seizure tests (maximal electroshock and pentylenetetrazole-induced seizure test) that aliskiren has a neutral or positive effect on the anticonvulsant efficacy of AEDs, which suggest its safe use for the treatment of high blood pressure in patients with epilepsy. The beneficial anticonvulsant effect of the concomitant treatment with aliskiren and valproate is worthy of recommendation to further both preclinical and clinical studies.

Efficacy and safety of a GABAergic drug (Gamalate® B6): effects on behavior and cognition in young adults with borderline-to-mild intellectual developmental disabilities and ADHD

BACKGROUND

We evaluated Gamalate® B6 (GB6) in patients with borderline intellectual functioning (BIF) or mild intellectual development disability (IDD).

PATIENTS AND METHODS

This was a prospective phase IV observational pilot study in 30 patients who underwent neuropsychological evaluation during treatment with GB6 for 12 weeks.

RESULTS

In comparison with baseline, the responses were positive, with a significant improvement in hyperactivity (51.7%), irritability (35.5%), and logorrhea (50%), and no sedative effect. The Clinical Global Impressions - Severity (CGI-S) score was much improved or very much improved in 73% of cases. Reaction time was better with fewer errors, thus indicating an improvement in attentional processes. A statistically significant result was obtained for the number of movements used to solve the problem and for the total number of correctly solved problems.

CONCLUSION

In this pilot study, GB6 was effective and well tolerated in cases of ADHD and challenging behavior in young adults with borderline-to-mild BIF/IDD. However, given the small number of patients involved and the uncontrolled nature of the study, these results should be viewed cautiously.

Mechanisms of action of currently used antiseizure drugs

Antiseizure drugs (ASDs) prevent the occurrence of seizures; there is no evidence that they have disease-modifying properties. In the more than 160 years that orally administered ASDs have been available for epilepsy therapy, most agents entering clinical practice were either discovered serendipitously or with the use of animal seizure models. The ASDs originating from these approaches act on brain excitability mechanisms to interfere with the generation and spread of epileptic hyperexcitability, but they do not address the specific defects that are pathogenic in the epilepsies for which they are prescribed, which in most cases are not well understood. There are four broad classes of such ASD mechanisms: (1) modulation of voltage-gated sodium channels (e.g. phenytoin, carbamazepine, lamotrigine), voltage-gated calcium channels (e.g. ethosuximide), and voltage-gated potassium channels [e.g. retigabine (ezogabine)]; (2) enhancement of GABA-mediated inhibitory neurotransmission (e.g. benzodiazepines, tiagabine, vigabatrin); (3) attenuation of glutamate-mediated excitatory neurotransmission (e.g. perampanel); and (4) modulation of neurotransmitter release via a presynaptic action (e.g. levetiracetam, brivaracetam, gabapentin, pregabalin). In the past two decades there has been great progress in identifying the pathophysiological mechanisms of many genetic epilepsies. Given this new understanding, attempts are being made to engineer specific small molecule, antisense and gene therapies that functionally reverse or structurally correct pathogenic defects in epilepsy syndromes. In the near future, these new therapies will begin a paradigm shift in the treatment of some rare genetic epilepsy syndromes, but targeted therapies will remain elusive for the vast majority of epilepsies until their causes are identified. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Self-motion perception is sensitized in vestibular migraine: pathophysiologic and clinical implications

Vestibular migraine (VM) is the most common cause of spontaneous vertigo but remains poorly understood. We investigated the hypothesis that central vestibular pathways are sensitized in VM by measuring self-motion perceptual thresholds in patients and control subjects and by characterizing the vestibulo-ocular reflex (VOR) and vestibular and headache symptom severity. VM patients were abnormally sensitive to roll tilt, which co-modulates semicircular canal and otolith organ activity, but not to motions that activate the canals or otolith organs in isolation, implying sensitization of canal-otolith integration. When tilt thresholds were considered together with vestibular symptom severity or VOR dynamics, VM patients segregated into two clusters. Thresholds in one cluster correlated positively with symptoms and with the VOR time constant; thresholds in the second cluster were uniformly low and independent of symptoms and the time constant. The VM threshold abnormality showed a frequency-dependence that paralleled the brain stem velocity storage mechanism. These results support a pathogenic model where vestibular symptoms emanate from the vestibular nuclei, which are sensitized by migraine-related brainstem regions and simultaneously suppressed by inhibitory feedback from the cerebellar nodulus and uvula, the site of canal-otolith integration. This conceptual framework elucidates VM pathophysiology and could potentially facilitate its diagnosis and treatment.

Effect of Long-term Carbamazepine Therapy on Bone Health

Introduction:

Recent research reported that prolonged use of AET is associated with changes in bone metabolism, with consequent reduction in bone mineral density (BMD) and increased risk of fractures.

Objectives:

Therefore, the aim of our study was to investigate the effects of carbamazepine on serum levels of 25 -hydroxyvitamin D and on biomarker of bone formation and resorption (serum levels of osteocalcin).

Material and methods:

We measured serum levels of 25-OHD and osteocalcin (OCLN) in normal controls (n=30) and in epilepsy patients taking carbamazepine (CBZ) (n=50) in monotherapy for a period of at least twelve months. For each participant, mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry method.

Results:

The average value of vitamin D in serum was significantly lower in CBZ group than in control group (Vit D 17.03+12.86 vs. 32.03+6.99, p=0.0001). The average value of osteocalcin in serum was significantly higher in CBZ group than in control group (26.06+10.78 vs. 19.64+6, 54, p=0.004).BMD value in CBZ group was significantly lower than in control group (T. score CBZ: 0.08+1.38 vs. T. score control: 0.73+ 1.13, p=0.031; Z score CBZ:-0.05+1.17 vs. Z. score control: 0.55+0.79, p=0.015).

Conclusion:

AEDs are associated with bone disease, as evidenced by biochemical abnormalities and decreased BMD. Patients on long-term antiepileptic therapy, especially with enzyme-inducing agents, could benefit of routine measurement of biochemical markers of bone turnover, and BMD measurement as part of osteoporosis investigation.

Valproic Acid Stimulates Hippocampal Neurogenesis via Activating the Wnt/β-Catenin Signaling Pathway in the APP/PS1/Nestin-GFP Triple Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by the deposition of amyloid-β (Aβ) peptides and neurofibrillary tangles (NFTs) and massive loss of neuronal cells in the brain. Adult hippocampus continuously generates new neurons throughout life to shape brain function and impaired neurogenesis may contribute to a series of cognitive deterioration associated with AD. Enhancing endogenous neurogenesis represents a promising strategy that may ameliorate AD-associated cognitive defects. However, neurogenesis-enhancing approaches and underlying mechanisms are still not well studied. Here, using a mouse model of AD amyloid precursor protein (APP/PS1/Nestin-GFP triple transgenic mice, 3xTgAD), we examined the effects of 4 weeks of valproic acid (VPA) treatment on hippocampal neurogenesis in 2- and 6-month-old mice. VPA treatment promoted cell proliferation and increased the density of immature neurons in the dentate gyrus (DG) of the hippocampus of 3xTgAD mice. Consistent with enhanced neurogenesis, behavioral and morphological analysis showed that VPA treatment improved the learning and memory ability of 3xTgAD mice. Mechanistically, VPA treatment increased β-catenin levels, accumulated the inactive form of glycogen synthase kinase-3β (GSK-3β), and induced the expression of NeuroD1, a Wnt target gene involved in neurogenesis, suggesting the activation of the Wnt signaling pathway in the hippocampus of 3xTgAD mice. This study indicates that VPA stimulates neurogenesis in the adult hippocampus of AD mice model through the Wnt pathway, highlighting VPA as a potential therapeutic for treating AD and related diseases.

Alterations in GABAA-Receptor Trafficking and Synaptic Dysfunction in Brain Disorders

GABA_A receptors (GABA_AR) are the major players in fast inhibitory neurotransmission in the central nervous system (CNS). Regulation of GABA_AR trafficking and the control of their surface expression play important roles in the modulation of the strength of synaptic inhibition. Different pieces of evidence show that alterations in the surface distribution of GABA_AR and dysregulation of their turnover impair the activity of inhibitory synapses. A diminished efficacy of inhibitory neurotransmission affects the excitatory/inhibitory balance and is a common feature of various disorders of the CNS characterized by an increased excitability of neuronal networks. The synaptic pool of GABA_AR is mainly controlled through regulation of internalization, recycling and lateral diffusion of the receptors. Under physiological condition these mechanisms are finely coordinated to define the strength of GABAergic synapses. In this review article, we focus on the alteration in GABA_AR trafficking with an impact on the function of inhibitory synapses in various disorders of the CNS. In particular we discuss how similar molecular mechanisms affecting the synaptic distribution of GABA_AR and consequently the excitatory/inhibitory balance may be associated with a wide diversity of pathologies of the CNS, from psychiatric disorders to acute alterations leading to neuronal death. A better understanding of the cellular and molecular mechanisms that contribute to the impairment of GABAergic neurotransmission in these disorders, in particular the alterations in GABA_AR trafficking and surface distribution, may lead to the identification of new pharmacological targets and to the development of novel therapeutic strategies.

Effect of gabapentin on sleep patterns disturbed by epilepsy

For a long time, numerous sleep alterations induced by nocturnal epilepsy have been described. Such alterations include sleep fragmentation, decrement of sleep efficiency, increment of the wake time after sleep onset (WASO), increment of light sleep, and decrement of sleep depth. On the other hand, gabapentin (GBP), an antiepileptic drug analog of γ-aminobutyric acid (GABA) used as adjunctive and eventually, as a monotherapeutic treatment, induces a significant improvement in patients with both focal and secondarily generalized partial seizures. In experimental epilepsy models, this drug protects against pentylenetetrazol (PTZ)-induced convulsions. In consideration of such GBP properties, the aim of this work was to investigate its efficacy to protect against sleep disturbances provoked by convulsive seizures induced by the administration of PTZ. Nine-hour (9-hour) polygraphic studies were carried out in chronically implanted male adult Wistar rats separated into 4 different groups of 6 individuals. Control recordings in each group were done after saline administration. One group received a SC Subcutaneous (SC) injection of 50 mg/kg of PTZ alone while the other three groups were injected with either 15, 30, or 60 mg/kg IP Intraperitoneal (IP) of GBP 30 min prior to PTZ (50 mg/kg SC) administration. Animals displayed the whole range of electrophysiological and behavioral manifestations of the disease during the epileptic episodes induced by PTZ administration, and the states of vigilance were significantly altered. Insomnia occurred immediately after PTZ injection preceding the appearance of the first epileptic symptoms. Thus, both slow wave sleep (SWS) and rapid eye movement sleep (REM sleep) were completely inhibited during a relatively long period of time. The disturbing effects of epilepsy on sleep decreased when animals were under GBP treatment. Improvement of sleep was dependent on the administered dose of this antiepileptic drug.

Effect of aliskiren, a direct renin inhibitor, on the protective action of antiepileptic drugs against pentylenetetrazole-induced clonic seizures in mice

It has been demonstrated that certain angiotensin-converting enzyme (ACE) inhibitors and angiotensin AT₁ receptor antagonists can possess anticonvulsant activity. The purpose of the current study was to examine the effect of aliskiren, a direct renin inhibitor and a novel antihypertensive drug, against pentylenetetrazole (PTZ)-induced clonic seizures in mice and on the protective activity of conventional antiepileptic drugs (AEDs) in this seizure model. Effects of aliskiren on the PTZ threshold and the protective efficacy of AEDs, such as clonazepam (CLO), phenobarbital (PB), valproate (VPA), and ethosuximide (ETX) in the PTZ test, were evaluated in adult Swiss mice. Aliskiren and AEDs were administered intraperitoneally (i.p.) while PTZ (50-100 mg/kg) was injected subcutaneously (s.c.). The rota-rod and passive avoidance test were used to assess the adverse effects of the combined treatment with aliskiren and AEDs. Aliskiren, at the dose of 75 mg/kg, significantly raised the PTZ threshold (P < 0.05). Furthermore, aliskiren, at the subthreshold dose of 50 mg/kg, significantly enhanced the protective action of CLO (P < 0.01), PB (P < 0.01), and VPA (P < 0.05) but not ETX (P > 0.05) in the s.c. PTZ test. Motor coordination in the rota-rod test and long-term memory in the passive avoidance task were not impaired by the combined treatment of the drugs. This study suggests that treatment with aliskiren can be useful in hypertensive patients with myoclonic seizures. Certainly, a clinical verification of using aliskiren in such patients would be necessary.

Vitamin D supplementation for bone health in adults with epilepsy: A systematic review

OBJECTIVE

Several antiepileptic drugs (AEDs) have been associated with a detrimental effect on bone health through a reduction in serum vitamin D. Subsequently, several studies have investigated the effect of vitamin D supplementation in persons with epilepsy being treated with AEDs. The present systematic review of published literature was conducted to determine the effect of vitamin D intervention on bone health in adults with epilepsy.

METHODS

The following databases were searched using keywords including but not limited to epilepsy, bone, and vitamin D: PubMed, Medline, Embase, Scopus, Cochrane Clinical Trials, International Pharmaceutical Abstracts, Health Canada Clinical Trials Database, ClinicalTrials.gov, EU Clinical Trials, and Google. Studies were eligible if there was an epilepsy diagnosis, participants were adults (18+ years old), and vitamin D treatment and bone outcome were provided. Articles were screened independently by 2 reviewers. Methodological quality was assessed using the Cochrane Collaboration's tool and a modified Newcastle Ottawa Scale for nonrandomized studies.

RESULTS

Nine studies were found to be eligible for this review. After vitamin D treatment, there appeared to be positive changes in bone turnover markers; 3 of 8 studies found the increase in serum calcium to be significant, 6 of 8 studies found the decrease in alkaline phosphatase to be significant, and 2 of 4 studies found the decrease in parathyroid hormone to be significant. All 6 studies that investigated bone mineralization had significant findings; however, due to varying methodologies, the impact of vitamin D on bone mineralization was inconclusive.

SIGNIFICANCE

Vitamin D does appear to have some benefit to bone health in adults with epilepsy, and therefore supplementation could potentially be a requisite to using some AEDs. To clarify the role of vitamin D supplementation to manage the adverse effect of AEDs on bone health in adults with epilepsy, long-term trials that use higher doses (>1800 IU) and measure bone mineral density are necessary.

Interactions of aliskiren, a direct renin inhibitor, with antiepileptic drugs in the test of maximal electroshock in mice

Experimental studies showed that certain angiotensin-converting enzyme inhibitors and angiotensin AT₁ receptor antagonists can decrease seizure severity in rodents. Additionally, some of these blockers of the renin-angiotensin system have been documented to enhance the anticonvulsant activity of antiepileptic drugs against maximal electroshock-induced seizures. The aim of the current study was to investigate the effect of aliskiren, a direct renin inhibitor and a novel antihypertensive drug, on the protective action of numerous antiepileptic drugs (carbamazepine, valproate, clonazepam, phenobarbital, oxcarbazepine, lamotrigine, topiramate and pregabalin) in the test of maximal electroshock in mice. The examined drugs were administered intraperitoneally. Aliskiren up to a dose of 75mg/kg did not affect the threshold for electroconvulsions, however, aliskiren (75mg/kg) enhanced the anticonvulsant action of clonazepam and valproate. Following aliskiren treatment, a higher brain concentration of valproate was noted, suggesting a pharmacokinetic interaction. In the rota-rod test, the concomitant treatment with aliskiren (50 or 75mg/kg) and clonazepam (22.6mg/kg) impaired motor coordination while clonazepam (22.6mg/kg) alone showed strong tendency towards this impairment. The combination of aliskiren (75mg/kg) with phenobarbital (25.5mg/kg) caused long-term memory deficits in the passive avoidance task. This study shows that there are no negative interactions between aliskiren and the examined antiepileptic drugs as concerns their anticonvulsant activity. Aliskiren even potentiated the anticonvulsant action of clonazepam and valproate against maximal electroshock. The impact of aliskiren alone on seizure activity or on the anticonvulsant and adverse activity of antiepileptic drugs needs further evaluation in other animal models of seizures.

Sensitive inexpensive HPLC determination of four antiepileptic drugs in human plasma: application to PK studies

Aim: Recently, polytherapy regimen has been introduced for the treatment of epileptic patients for better seizure control with lesser side effects and better control of multiple seizure types. Methodology: A simple, sensitive and highly specific reversed-phase HPLC method was developed for simultaneous determination of four antiepileptic drugs (AEDs), levetiracetam, lamotrigine, oxcarbazepine and carbamazepine, in real human plasma without interference from endogenous components of plasma. Conclusion: The method was proved to be linear in the range of 0.5–50 µg/ml for all drugs. It was successfully applied for clinical PK study of the AEDs in healthy volunteers following single administration. Also, this method was applied for simultaneous determination of the studied drugs in volunteers’ plasma receiving synergistic binary combinations from the four AEDs when used as add-on therapy. The good precision and selectivity of the developed method allow it to be used for routine therapeutic drug monitoring of such drugs as a useful tool in epilepsy management.

Mexiletine and its Interactions with Classical Antiepileptic Drugs: An Isobolographic Analysis

Using the mouse maximal electroshock test, the reference model of tonic-clonic seizures, the aim of the present study was to determine the type of interaction between mexiletine (a class IB antiarrhythmic drug) and classical antiepileptics: valproate, carbamazepine, phenytoin, and phenobarbital. Isobolographic analysis of obtained data indicated antagonistic interactions between mexiletine and valproate (for fixed ratio combinations of 1:1 and 3:1). Additivity was observed between mexiletine and valproate applied in proportion of 1:3 as well as between mexiletine and remaining antiepileptics for the fixed ratios of 1:3, 1:1, and 3:1. Neither motor performance nor long-term memory were impaired by mexiletine or antiepileptic drugs regardless of whether they were administered singly or in combination. Mexiletine did not significantly affected brain concentrations of carbamazepine, phenobarbital or phenytoin. In contrast, the antiarrhythmic drug decreased by 23 % the brain level of valproate. This could be, at least partially, the reason of antagonistic interaction between the two drugs. In conclusion, the observed additivity suggests that mexiletine can be safely applied in epileptic patients treated with carbamazepine, phenytoin or phenobarbital. Because of undesirable pharmacodynamics and pharmacokinetic interactions with valproate, mexiletine should not be used in such combinations.

Prospects of epileptogenesis prevention

Epilepsy is a common neurologic disease, affecting about 1-2% of the population. In around 30% of patients with epilepsy, their seizures are not satisfactorily controlled and drug-resistant epilepsy constitutes a real therapeutic challenge. Consequently, there are efforts aimed at the inhibition of epileptogenesis, a process of converting a normal into an epileptic brain. Data on this problem have been mainly obtained in post-status epilepticus rodent models in which spontaneous seizure activity and behavioral disturbances develop over time. Among antiepileptic drugs, diazepam at high dose of 20mg/kg given during status epilepticus, significantly inhibited the development of spontaneous seizures and also, a strong neuroprotective effect was evident. Also gabapentin and valproate (over a period of 40 days) proved effective in the inhibition of spontaneous seizure activity and reduction of behavioral deficit. However, there are also data that valproate (over 28 days) significantly improved the behavioral performance without affecting the occurrence of spontaneous seizures. A number of antiepileptic drugs, carbamazepine, lamotrigine, levetiracetam, phenobarbital, and topiramate were completely ineffective. Among non-antiepileptic drugs, some promise show rapamycin, losartan and combinations of anti-inflammatory drugs, targeting different inflammatory pathways. Inhibition of epileptogenesis may become a valuable therapeutic approach provided that there are reliable markers of this process. Actually, such markers begin to emerge.

Low-dose topiramate in alcohol dependence: a single-blind, placebo-controlled study

INTRODUCTION

Topiramate (TOP) and anticonvulsants in general are considered safe and effective drugs for the treatment of alcohol dependence, even though TOP-induced adverse events are quite common, especially for high initial doses or if titration to 300 mg/d is too rapid. The aim of the present study was to assess the efficacy and tolerability profile of low-dose TOP for relapse prevention.

METHODS

After detoxification, 52 patients were randomized into 2 groups as follows: 26 patients received 100 mg of TOP (oral, twice daily), titrated over 2 weeks, and 26 patients received placebo (PLA). Both groups underwent rehabilitation twice a week.

RESULTS

After 6 weeks of treatment, compared with the PLA group, patients receiving TOP showed the following: (1) fewer drinking days (P < 0.05); (2) less daily alcohol consumption (P < 0.05); (3) more days of treatment (P < 0.05); (4) reduced levels of craving (Obsessive-Compulsive Drinking Scale) and withdrawal symptoms (Clinical Institute Withdrawal Assessment for Alcohol-Revised); and (5) improvement of anxiety, depression, and obsessive-compulsive symptom severity (Symptom Check List 90 Revised).

CONCLUSIONS

Despite the small sample size and the short follow-up period, the present PLA-controlled study demonstrated the potential usefulness of TOP, even when administered at a dosage of 100 mg/d, for the treatment of detoxified alcohol-dependent subjects, confirming results from previous studies testing higher doses of TOP.

Studies on the anticonvulsant activity of 4-alkyl-1,2,4-triazole-3-thiones and their effect on GABAergic system

A series of 4-alkyl-5-(3-chlorobenzyl/2,3-dichlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (1a-14a) were designed, synthesized and screened for their anticonvulsant properties. Moreover, the acute adverse-effect profile of the active compounds (1a-7a, 12a) with respect to impairment of motor performance was evaluated in the chimney test. Among 4-alkyl-5-(3-chlorobenzyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones, ethyl, butyl, pentyl, hexyl, and heptyl derivatives administered intraperitoneally in a dose of 300 mg/kg protected 100% of the tested animals at four pretreatment times (i.e., 15, 30, 60, 120 min). Taking into account the median effective and toxic doses as well as the time-course profile of anticonvulsant activity, 5-(3-chlorobenzyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (4a) was proposed as the best tolerated and the most promising potential drug candidate. Finally, a radioligand binding assay was used to check whether the anticonvulsant activity of 4-alkyl-1,2,4-triazole-3-thiones was a result of their interactions (direct or allosteric) with GABAA receptor complex and/or their affinity to benzodiazepine (BDZ) binding sites.

Studies on the anticonvulsant activity and influence on GABA-ergic neurotransmission of 1,2,4-triazole-3-thione- based compounds

The anticonvulsant activity of several 1,2,4-triazole-3-thione derivatives on mouse maximal electroshock-induced seizures was tested in this study. Characteristic features of all active compounds were rapid onset of action and long lasting effect. Structure-activity observations showed that the probability of obtaining compounds exerting anticonvulsant activity was much higher when at least one of the phenyl rings attached to 1,2,4-triazole nucleus had a substituent at the para position. The obtained results, moreover, permit us to conclude that despite the structural similarity of loreclezole (second-generation anticonvulsant drug) and the titled compounds, their anticonvulsant activity is achieved via completely different molecular mechanisms.

Soybean greatly reduces valproic acid plasma concentrations: a food-drug interaction study

The aim of this study was to investigate the effects of soy on the pharmacokinetics and pharmacodynamics of valproic acid (VPA). In a preclinical study, rats were pretreated with two different amounts of soy extract for five days (150 mg/kg and 500 mg/kg), which resulted in decreases of 57% and 65% in the Cmax of VPA, respectively. AUC of VPA decreased to 83% and 70% in the soy pretreatment groups. Interestingly, the excretion rate of VPA glucuronide (VPAG) was higher in the soy-fed groups. Levels of UDP-glucuronosyltransferase (UGT) UGT1A3, UGT1A6, UGT2B7 and UGT2B15 were elevated in the soy-treated group, and GABA concentrations were elevated in the brain after VPA administration. However, this was less pronounced in soy extract pretreated group than for the untreated group. This is the first study to report the effects of soy pretreatment on the pharmacokinetics and pharmacodynamics of VPA in rodents.

Valproic acid reduces neuritic plaque formation and improves learning deficits in APP(Swe) /PS1(A246E) transgenic mice via preventing the prenatal hypoxia-induced down-regulation of neprilysin

AIMS

Previously, we have documented that prenatal hypoxia can aggravate the cognitive impairment and Alzheimer's disease (AD) neuropathology in APP(Swe) /PS1(A246E) (APP/PS1) transgenic mice, and valproic acid (VPA) can prevent hypoxia-induced down-regulation of β-amyloid (Aβ) degradation enzyme neprilysin (NEP) in primary neurons. In this study, we have investigated the molecular mechanisms of VPA's anti-AD effects and found that VPA can reduce the prenatal hypoxia-induced neuritic plaque formation and improve the learning deficits in the AD mouse model.

METHODS

The pregnant APP/PS1 transgenic mice were exposed in a hypobaric chamber. Neuritic plaque staining, Morris water maze, and enzyme-linked immunosorbent assay (ELISA) were used to detect the effects of VPA on Aβ neuropathology, learning, and memory. Chromatin immunoprecipitation (ChIP) assays and real-time PCR (RT-PCR) were used to determine the effect of VPA on the histone3 acetylation (H3-Ace).

RESULTS

We found that VPA can inhibit neuritic plaque formation and improve the learning and memory in the prenatal hypoxic APP/PS1 transgenic mice. In addition, VPA treatment can decrease the soluble and insoluble Aβ42 levels and increase the NEP expression via up-regulation of H3-Ace in the APP/PS1 transgenic mice.

CONCLUSION

Valproic acid is able to attenuate the prenatal hypoxia-induced Aβ neuropathology and learning and memory deficits via inhibiting the activation of histone deacetylase 1 (HDAC1), preventing the decrease in H3-Ace in the NEP promoter regions and reducing the down-regulation of NEP.

Certain secondary antiepileptic drugs can rescue hippocampal injury following a critical growth period despite poor anticonvulsant activity and cognitive deficits

Clinical and experimental studies have shown that many common secondary antiepileptic drugs (AEDs) are ineffective at blocking seizures in adulthood; however, some afford neuroprotection. In early development, certain AEDs cause apoptosis; however, it is unknown whether these drugs are neurotoxic to the juvenile brain following a developmentally regulated proapoptotic period and whether they alter the seizure threshold, seizure-induced neuronal vulnerability, and/or cognitive function. Lamotrigine (LTG), carbamazepine (CBZ), phenytoin (PHT), valproate (VPA), and topiramate (TPM) were systemically administered to rat pups for 7days beginning on postnatal (P) day 14 (P14), then half the animals were injected with kainate (KA) to trigger seizures, an age when the CA1 subregion becomes preferentially sensitive to status epilepticus. Histological outcome, seizure severity, and learning and memory were determined with an electroencephalograph (EEG), silver impregnation, and a water-maze swim task. None of the AEDs tested significantly attenuated behavioral or electrographic seizures. Phenytoin increased mortality, identifying a detrimental side effect of this drug. The other drugs (LTG, VPA, TPM, and CBZ) afforded different amounts of protection to the CA1 subregion but not to the CA3 subregion or extrahippocampal structures. With the exception of VPA, AED-treated animals lagged behind during swim task acquisition. All groups improved in the water-maze swim task over time, particularly on the last trials; however, the average escape latency was still impaired for TPM-treated animals and all AED+KA-treated groups. Thus, while certain AEDs demonstrated some neuroprotective effects, poor antiepileptic activity, memory impairment, and other deleterious side effects were observed with these drugs suggesting that the search for potentially more effective and tolerated agents is essential for improving clinical outcome in children and adolescents with epilepsy.

Effect of 1-methyl-1,2,3,4-tetrahydroisoquinoline on the protective action of various antiepileptic drugs in the maximal electroshock-induced seizure model: a type II isobolographic analysis

The aim of this study was to characterize the interaction between 1-methyl-1,2,3,4-tetrahydroisoquinoline (1-MeTHIQ-an endogenous parkinsonism-preventing substance) and various antiepileptic drugs [AEDs: clonazepam (CZP), ethosuximide (ETS), gabapentin (GBP), levetiracetam (LEV), tiagabine (TGB) and vigabatrin (VGB)] in the mouse maximal electroshock (MES)-induced seizure model. Results indicate that 1-MeTHIQ in combination with CZP (at the fixed ratios of 50:1 and 25:1), ETS (1:10) and GBP (1:1, 1:2, 1:5 and 1:10) exerted supra-additive (synergistic) interactions in the mouse MES model. In contrast, 1-MeTHIQ in combination with CZP (200:1 and 100:1), ETS (1:1, 1:2 and 1:5), LEV and VGB (1:1, 1:2, 1:5 and 1:10), and TGB (200:1, 100:1, 50:1 and 25:1) produced additive interaction in the mouse MES model. Total brain AED concentrations were unaffected by 1-MeTHIQ, and inversely, CZP, ETS and GBP had no impact on total brain concentrations of 1-MeTHIQ, indicating pharmacodynamic nature of synergistic interactions between 1-MeTHIQ and the tested AEDs in the mouse MES model. In conclusion, the supra-additive interactions of 1-MeTHIQ with CZP (at the fixed ratios of 50:1 and 25:1), ETS (1:10) and GBP (1:1, 1:2, 1:5 and 1:10) in the mouse MES model appear to be particularly favorable combinations from a clinical viewpoint. The additive combinations of 1-MeTHIQ with CZP (100:1, 50:1), ETS (1:1, 1:2 and 1:5), LEV and VGB (1:1, 1:2, 1:5, and 1:10), and TGB (200:1, 100:1, 50:1 and 25:1) seem to be neutral and worthy of consideration in further clinical practice.

Loss of hippocampal interneurons and epileptogenesis: a comparison of two animal models of acquired epilepsy

Reduced hippocampal GABAergic inhibition is acknowledged to be associated with epilepsy. However, there are no studies that had quantitatively compared the loss of various interneuron populations in different models of epilepsy. We tested a hypothesis that the more severe the loss of hippocampal interneurons, the more severe was the epilepsy. Epileptogenesis was triggered in adult rats by status epilepticus (SE) (56 SE, 24 controls) or by traumatic brain injury (TBI) (45 TBI, 23 controls). The total number of hippocampal parvalbumin (PARV), cholecystokinin (CCK), calretinin (CR), somatostatin (SOM), or neuropeptide Y (NPY) positive neurons was estimated using unbiased stereology at 1 or 6 months post-insult. The rats with TBI had no spontaneous seizures but showed increased seizure susceptibility. Eleven of the 28 rats (39 %) in the SE group had spontaneous seizures. The most affected hippocampal area after TBI was the ipsilateral dentate gyrus, where 62 % of PARV-immunoreactive (ir) (p < 0.001 compared to controls), 77 % of CR-ir (p < 0.05), 46 % of SOM-ir (p < 0.001), and 59 % of NPY-ir (p < 0.001) cells remained at 1 month after TBI. At 6 months post-TBI, only 35 % of PARV-ir (p < 0.001 compared to controls), 63 % of CCK-ir (p < 0.01), 74 % of CR-ir (p < 0.001), 55 % of SOM-ir (p < 0.001), and 51 % of NPY-ir (p < 0.001) cells were remaining. Moreover, the reduction in PARV-ir, CCK-ir, and CR-ir neurons was bilateral (all p < 0.05). Substantial reductions in different neuronal populations were also found in subfields of the CA3 and CA1. In rats with epilepsy after SE, the number of PARV-ir neurons was reduced in the ipsilateral CA1 (80 % remaining, p < 0.05) and the number of NPY-ir neurons bilaterally in the dentate gyrus (33-37 %, p < 0.01) and the CA3 (54-57 %, p < 0.05). Taken together, interneuron loss was substantially more severe, widespread, progressive, and included more interneuron subclasses after TBI than after SE. Interneurons responsible for perisomatic inhibition were more vulnerable to TBI than those providing dendritic inhibition. Unlike expected, we could not demonstrate any etiology-independent link between the severity of hippocampal interneuron loss and the overall risk of spontaneous seizures.

Topiramate: Effects on cognition in patients with epilepsy, migraine headache and obesity

This paper reviews the clinical implications of topiramate (TPM)-induced cognitive deficits in patients with epilepsy, migraine headache, obesity, and in normal populations, followed by reviews of the literature describing the reversal of such deficits upon medication discontinuation. It also discusses animal investigations of TPM's role of neuroprotection in brain injury. TPM's most intolerable adverse effects (AEs) are on verbal fluency and reaction time, resulting in high discontinuation rates in patients taking it for epilepsy and migraine headache. However, because TPM is so effective in the treatment of epilepsy and migraine headache, its use is expected to continue. There appears to be greater tolerance of TPM's cognitive AEs when it is used in the treatment of obesity, perhaps because of the lower doses required. Research attempting to predict the populations most vulnerable to the cognitive effects caused by TPM is ongoing. Studies suggest that one such population may include patients with a past psychiatric history. Slow titration and administration of the lowest possible doses may decrease risk of cognitive deficits.

Trichosanthes tricuspidata modulates oxidative toxicity in brain hippocampus against pilocarpine induced status epilepticus in mice

Epilepsy prevails to be a neurological disorder in anticipation of safer drugs with enhanced anticonvulsant efficacy as presently available drugs fails to offer adequate control of epileptic seizures in about one-third of patients. The objective of this study was to evaluate the effect of Trichosanthes tricuspidata methanolic extract (TTME) against epilepsy mediated oxidative stress in pilocarpine induced mice. Intraperitonial administration of pilocarpine (85 mg/kg) induced seizure in mice was assessed by behavior observations, which is significantly (p < 0.05) reduced by TTME (100 and 200 mg/kg; i.p) in a dose dependant manner, similar to diazepam. Seizure was accompanied by significant increase in lipid peroxidation and the hippocampal nitrite content in pilocarpine group when compared with control. Moreover, the antioxidant enzymes superoxide dismutase, catalase and glutathione levels were decreased in pilocarpine administered groups. TTME administration attenuated oxidative damage as evident by decreased lipid oxidative damage and nitrite-nitrate content and restored the level of enzymatic antioxidant defenses in hippocampus. Involvement of free radicals during epilepsy is further confirmed by histopathological analysis which showed the loss of neuronal cells in hippocampus CA1 and CA3 pyramidal region. Our findings strongly support the hypothesis that TTME has anticonvulsant activity accompanied with the strong antioxidant potential plays a crucial role in reducing the oxidative stress produced by seizure.

Topiramate's effects on cocaine-induced subjective mood, craving and preference for money over drug taking

Topiramate, presumably through antagonism of excitatory glutaminergic pathways and facilitation of inhibitory gamma-aminobutyric acid neurons in the cortico-mesolimbic system, might reduce cocaine's abuse liability. We tested whether topiramate (100 mg twice daily) would reduce the euphoria, subjective mood, craving and preference for cocaine over money induced by low and high doses (0.325 and 0.65 mg/kg i.v., respectively) of experimentally administered cocaine in 24 male and female, cocaine-dependent, non-treatment-seeking research volunteers in a university in-patient laboratory. We utilized a randomized, double-blind, placebo-controlled, within-subject, Latin-square cross-over design in which three experimental challenge doses of low-dose cocaine, high-dose cocaine and placebo were administered in counterbalanced order after 5 days of topiramate or matching placebo pre-treatments separated by a 1-week washout period (2006-2009). After placebo pre-treatments, cocaine produced dose-related increases in euphoria, stimulant effects, craving for more cocaine and monetary value of cocaine in a behavioral preference test of cocaine versus money choice. Topiramate pre-treatment reduced the cocaine-related craving and monetary value of high-dose cocaine while increasing the monetary value, euphoria and stimulant effects of low-dose cocaine. Validated and standardized human experimental methods evaluating the potential for topiramate to alter cocaine's abuse liability suggest that topiramate may reduce the reinforcing effects and craving induced by higher cocaine doses. Low-dose cocaine might appear to have some enhancement of its stimulant properties in the presence of topiramate's prominent sedative effects.