Topiramate selectively protects against seizures induced by ATPA, a GluR5 kainate receptor agonist

Neurotransmitters crosstalk and regulation in the reward circuit of subjects with behavioral addiction

Behavioral addictive disorders (BADs) have become a significant societal challenge over time. The central feature of BADs is the loss of control over engaging in and continuing behaviors, even when facing negative consequences. The neurobiological underpinnings of BADs primarily involve impairments in the reward circuitry, encompassing the ventral tegmental area, nucleus accumbens in the ventral striatum, and prefrontal cortex. These brain regions form networks that communicate through neurotransmitter signaling, leading to neurobiological changes in individuals with behavioral addictions. While dopamine has long been associated with the reward process, recent research highlights the role of other key neurotransmitters like serotonin, glutamate, and endorphins in BADs' development. These neurotransmitters interact within the reward circuitry, creating potential targets for therapeutic intervention. This improved understanding of neurotransmitter systems provides a foundation for developing targeted treatments and helps clinicians select personalized therapeutic approaches.

Increased GluK1 Subunit Receptors in Corticostriatal Projection from the Anterior Cingulate Cortex Contributed to Seizure-Like Activities

The corticostriatal connection plays a crucial role in cognitive, emotional, and motor control. However, the specific roles and synaptic transmissions of corticostriatal connection are less studied, especially the corticostriatal transmission from the anterior cingulate cortex (ACC). Here, a direct glutamatergic excitatory synaptic transmission in the corticostriatal projection from the ACC is found. Kainate receptors (KAR)-mediated synaptic transmission is increased in this corticostriatal connection both in vitro and in vivo seizure-like activities. GluK1 containing KARs and downstream calcium-stimulated adenylyl cyclase subtype 1 (AC1) are involved in the upregulation of KARs following seizure-like activities. Inhibiting the activities of ACC or its corticostriatal connection significantly attenuated pentylenetetrazole (PTZ)-induced seizure. Additionally, injection of GluK1 receptor antagonist UBP310 or the AC1 inhibitor NB001 both show antiepileptic effects. The studies provide direct evidence that KARs are involved in seizure activity in the corticostriatal connection and the KAR-AC1 signaling pathway is a potential novel antiepileptic strategy.

NMDA Receptors: Distribution, Role, and Insights into Neuropsychiatric Disorders

BACKGROUND

N-methyl-D-aspartate receptors (NMDARs) are members of the ionotropic glutamate receptor family. These ligand-gated channels are entwined with numerous fundamental neurological functions within the central nervous system (CNS), and numerous neuropsychiatric disorders may arise from their malfunction.

METHODS

The purpose of the present review is to provide a detailed description of NMDARs by addressing their molecular structures, activation mechanisms, and physiological roles in the mammalian brain. In the second part, their role in various neuropsychiatric disorders including stroke, epilepsy, anti-NMDA encephalitis, Alzheimer's and Huntington's diseases, schizophrenia, depression, neuropathic pain, opioid-induced tolerance, and hyperalgesia will be covered.

RESULTS

Finally, through a careful exploration of the main non-competitive NMDARs antagonists (channel-blockers).

CONCLUSION

We discuss the strengths and limitations of the various molecular structures developed for diagnostic or therapeutic purposes.

Targeting the Multiple Complex Processes of Hypoxia-Ischemia to Achieve Neuroprotection

Hypoxic-ischemic encephalopathy (HIE) is a major cause of newborn brain damage stemming from a lack of oxygenated blood flow in the neonatal period. Twenty-five to fifty percent of asphyxiated infants who develop HIE die in the neonatal period, and about sixty percent of survivors develop long-term neurological disabilities. From the first minutes to months after the injury, a cascade of events occurs, leading to blood-brain barrier (BBB) opening, neuronal death and inflammation. To date, the only approach proposed in some cases is therapeutic hypothermia (TH). Unfortunately, TH is only partially protective and is not applicable to all neonates. This review synthesizes current knowledge on the basic molecular mechanisms of brain damage in hypoxia-ischemia (HI) and on the different therapeutic strategies in HI that have been used and explores a major limitation of unsuccessful therapeutic approaches.

Emerging therapeutic strategies in hypoxic-ischemic encephalopathy: a focus on cognitive outcomes

Perinatal hypoxia-ischemia represents a significant risk to CNS development, leading to high mortality rates, diverse damages, and persistent neurological deficits. Despite advances in neonatal medicine in recent decades, the incidence of HIE remains substantial. Motor deficits can manifest early, while cognitive impairments may be diagnosed later, emphasizing the need for extended follow-up. This review aims to explore potential candidates for therapeutic interventions for hypoxic-ischemic encephalopathy (HIE), with a focus on cognitive deficits. We searched randomized clinical trials (RCT) that tested drug treatments for HIE and evaluated cognitive outcomes. The results included studies on erythropoietin, melatonin, magnesium sulfate, topiramate, and a combination of vitamin C and ibuprofen. Although there are several indications of the efficacy of these drugs among animal models, considering neuroprotective properties, the RCTs failed to provide complete effectiveness in the context of cognitive impairments derived from HIE. More robust RCTs are still needed to advance our knowledge and to establish standardized treatments for HIE.

Delving into the significance of the His289Tyr single-nucleotide polymorphism in the glutamate ionotropic receptor kainate-1 (Grik1) gene of a genetically audiogenic seizure model

Genetic abnormalities affecting glutamate receptors are central to excitatory overload-driven neuronal mechanisms that culminate in seizures, making them pivotal targets in epilepsy research. Increasingly used to advance this field, the genetically audiogenic seizure hamster from Salamanca (GASH/Sal) exhibits generalized seizures triggered by high-intensity acoustic stimulation and harbors significant genetic variants recently identified through whole-exome sequencing. Here, we addressed the influence of the missense single-nucleotide polymorphism (C9586732T, p.His289Tyr) in the glutamate receptor ionotropic kainate-1 (Grik1) gene and its implications for the GASH/Sal seizure susceptibility. Using a protein 3D structure prediction, we showed a potential effect of this sequence variation, located in the amino-terminal domain, on the stability and/or conformation of the kainate receptor subunit-1 protein (GluK1). We further employed a multi-technique approach, encompassing gene expression analysis (RT-qPCR), Western blotting, and immunohistochemistry in bright-field and confocal fluorescence microscopy, to investigate critical seizure-associated brain regions in GASH/Sal animals under seizure-free conditions compared to matched wild-type controls. We detected disruptions in the transcriptional profile of the Grik1 gene within the audiogenic seizure-associated neuronal network. Alterations in GluK1 protein levels were also observed in various brain structures, accompanied by an unexpected lower molecular weight band in the inferior and superior colliculi. This correlated with substantial disparities in GluK1-immunolabeling distribution across multiple brain regions, including the cerebellum, hippocampus, subdivisions of the inferior and superior colliculi, and the prefrontal cortex. Notably, the diffuse immunolabeling accumulated within perikarya, axonal fibers and terminals, exhibiting a prominent concentration in proximity to the cell nucleus. This suggests potential disturbances in the GluK1-trafficking mechanism, which could subsequently affect glutamate synaptic transmission. Overall, our study sheds light on the genetic underpinnings of seizures and underscores the importance of investigating the molecular mechanisms behind synaptic dysfunction in epileptic neural networks, laying a crucial foundation for future research and therapeutic strategies targeting GluK1-containing kainate receptors.

GluK2 Is a Target for Gene Therapy in Drug-Resistant Temporal Lobe Epilepsy

OBJECTIVE

Temporal lobe epilepsy (TLE) is characterized by recurrent seizures generated in the limbic system, particularly in the hippocampus. In TLE, recurrent mossy fiber sprouting from dentate gyrus granule cells (DGCs) crea an aberrant epileptogenic network between DGCs which operates via ectopically expressed GluK2/GluK5-containing kainate receptors (KARs). TLE patients are often resistant to anti-seizure medications and suffer significant comorbidities; hence, there is an urgent need for novel therapies. Previously, we have shown that GluK2 knockout mice are protected from seizures. This study aims at providing evidence that downregulating KARs in the hippocampus using gene therapy reduces chronic epileptic discharges in TLE.

METHODS

We combined molecular biology and electrophysiology in rodent models of TLE and in hippocampal slices surgically resected from patients with drug-resistant TLE.

RESULTS

Here, we confirmed the translational potential of KAR suppression using a non-selective KAR antagonist that markedly attenuated interictal-like epileptiform discharges (IEDs) in TLE patient-derived hippocampal slices. An adeno-associated virus (AAV) serotype-9 vector expressing anti-grik2 miRNA was engineered to specifically downregulate GluK2 expression. Direct delivery of AAV9-anti grik2 miRNA into the hippocampus of TLE mice led to a marked reduction in seizure activity. Transduction of TLE patient hippocampal slices reduced levels of GluK2 protein and, most importantly, significantly reduced IEDs.

INTERPRETATION

Our gene silencing strategy to knock down aberrant GluK2 expression demonstrates inhibition of chronic seizure in a mouse TLE model and IEDs in cultured slices derived from TLE patients. These results provide proof-of-concept for a gene therapy approach targeting GluK2 KARs for drug-resistant TLE patients. ANN NEUROL 2023;94:745-761.

Kainate Receptor Antagonists: Recent Advances and Therapeutic Perspective

Since the 1990s, ionotropic glutamate receptors have served as an outstanding target for drug discovery research aimed at the discovery of new neurotherapeutic agents. With the recent approval of perampanel, the first marketed non-competitive antagonist of AMPA receptors, particular interest has been directed toward 'non-NMDA' (AMPA and kainate) receptor inhibitors. Although the role of AMPA receptors in the development of neurological or psychiatric disorders has been well recognized and characterized, progress in understanding the function of kainate receptors (KARs) has been hampered, mainly due to the lack of specific and selective pharmacological tools. The latest findings in the biology of KA receptors indicate that they are involved in neurophysiological activity and play an important role in both health and disease, including conditions such as anxiety, schizophrenia, epilepsy, neuropathic pain, and migraine. Therefore, we reviewed recent advances in the field of competitive and non-competitive kainate receptor antagonists and their potential therapeutic applications. Due to the high level of structural divergence among the compounds described here, we decided to divide them into seven groups according to their overall structure, presenting a total of 72 active compounds.

Anti-Inflammatory Effect of Topiramate in a Chronic Model of TNBS-Induced Colitis

Inflammatory bowel disease (IBD) is characterized by a chronic and relapsing inflammatory response in the gastrointestinal tract, resulting in severe symptoms such as abdominal pain, vomiting, diarrhea, bloody stools, and weight loss. Currently, there is no cure, and the pharmacological treatment includes drugs that induce and keep the patient in remission, not reversing the underlying pathogenic mechanism. These therapies, in the long term, may cause various side effects and complications, which has increased the need to investigate new, more effective, and safer pharmacological approaches. In preclinical studies, topiramate has demonstrated a potential anti-inflammatory effect by inhibiting the production of several pro-inflammatory cytokines. This study aimed to investigate the effect of topiramate in a chronic TNBS-induced colitis model in rodents. Experimental colitis was induced by four intrarectal administrations of 1% TNBS in female CD-1 mice. Topiramate 10 and 20 mg were administered intraperitoneally for 14 days. Several parameters were evaluated, such as bodyweight, alkaline phosphatase (ALP), fecal hemoglobin, fecal calprotectin, tumor necrosis factor (TNF)-α, and interleukin (IL)-10. Topiramate reduces TNBS-induced colonic damage in a model of chronic experimental colitis and normalizes the stool consistency and anus appearance. Additionally, topiramate significantly reduced the concentration of ALP, fecal hemoglobin, fecal calprotectin, TNF-α, and IL-10, demonstrating it to be a promising pharmacological approach for the treatment of IBD in the future.

Antagonism of GluK1-containing kainate receptors reduces ethanol consumption by modulating ethanol reward and withdrawal

Alcohol use disorder (AUD) is a neuropsychiatric condition affecting millions of people worldwide. Topiramate (TPM) is an antiepileptic drug that has been shown to reduce ethanol drinking in humans. However, TPM is associated with a variety of adverse effects due to its interaction with many receptor systems and intracellular pathways. GluK1-containing kainate receptors (GluK1*KARs) are non-selectively inhibited by TPM, and genetic association studies suggest that this receptor system could be targeted to reduce drinking in AUD patients. We examined the efficacy of LY466195, a selective inhibitor of GluK1*KAR, in reducing ethanol consumption in the intermittent two-bottle choice paradigm in mice. The effect of LY466195 on various ethanol-related phenotypes was investigated by quantification of alcohol intake, physical signs of withdrawal, conditioned place preference (CPP) and in vivo microdialysis in the nucleus accumbens. Selective GluK1*KAR inhibition reduced ethanol intake and preference in a dose-dependent manner. LY466195 treatment attenuated the physical manifestations of ethanol withdrawal and influenced the rewarding properties of ethanol. Interestingly, LY466195 injection also normalized changes in dopamine levels in response to acute ethanol in ethanol-dependent mice, but had no effect in ethanol-naïve mice, suggesting ethanol state-dependent effects. The data point to GluK1*KARs as an attractive pharmacological target for the treatment of AUD.

Kainate and AMPA receptors in epilepsy: Cell biology, signalling pathways and possible crosstalk

Epilepsy is caused when rhythmic neuronal network activity escapes normal control mechanisms, resulting in seizures. There is an extensive and growing body of evidence that the onset and maintenance of epilepsy involves alterations in the trafficking, synaptic surface expression and signalling of kainate and AMPA receptors (KARs and AMPARs). The KAR subunit GluK2 and AMPAR subunit GluA2 are key determinants of the properties of their respective assembled receptors. Both subunits are subject to extensive protein interactions, RNA editing and post-translational modifications. In this review we focus on the cell biology of GluK2-containing KARs and GluA2-containing AMPARs and outline how their regulation and dysregulation is implicated in, and affected by, seizure activity. Further, we discuss role of KARs in regulating AMPAR surface expression and plasticity, and the relevance of this to epilepsy. This article is part of the special issue on 'Glutamate Receptors - Kainate receptors'.

Combined analysis of the moderating effect of a GRIK1 polymorphism on the effects of topiramate for treating alcohol use disorder

BACKGROUND

In an initial study, we reported that topiramate reduced heavy drinking among individuals who sought to reduce their drinking and that the effect was moderated by a single nucleotide polymorphism (SNP; rs2832407) in GRIK1, which encodes the kainate GluK1 receptor subunit (Kranzler et al., 2014). In a subsequent study that prospectively randomized patients to medication group based on their rs2832407 genotype, we replicated the main effect of topiramate but not the moderating effect of the SNP (Kranzler et al., 2021). Given the similar design of the two studies, here we combined the findings to provide greater statistical power to test the pharmacogenetic effect.

MATERIAL AND METHODS

This secondary analysis of two 12-week, randomized controlled trials of topiramate included a total of 292 European-ancestry individuals (67.1 % male; topiramate: 48.3 %, placebo: 51.7 %) with problematic alcohol use. Using MANOVA, we examined changes in self-reported alcohol consumption, problems resulting from alcohol use, and quality of life, and the biomarker γ-glutamyltransferase. To test the pharmacogenetic hypothesis, all patients were genotyped for rs2832407.

RESULTS

There was a significant overall effect of topiramate on the alcohol-related outcomes (partial η2 = 0.134, p < 0.001), with follow-up analyses showing significant reductions in percent heavy drinking days (Cohen's d = 0.49), percent days abstinent (d = 0.23), drinks/day (d = 0.29) and alcohol-related problems (d = 0.45). Overall, the moderating effect of the SNP was non-significant (partial η² = 0.026, p = 0.37).

CONCLUSIONS

Although topiramate is an efficacious medication for reducing drinking and alcohol-related problems among patients with problematic alcohol use, rs2832407 does not appear to moderate its therapeutic effects. www.clinicaltrials.gov registrations: NCT00626925 and NCT02371889.

Prospective randomized pharmacogenetic study of topiramate for treating alcohol use disorder

In a prior study, topiramate reduced heavy drinking among individuals who sought to reduce their drinking, with the effect moderated by a single nucleotide polymorphism (SNP; rs2832407) in GRIK1, which encodes the kainate GluK1 receptor subunit (Kranzler et al. 2014). The present study sought to replicate prospectively the effect of topiramate and rs2832407 in patients with DSM-5 alcohol use disorder (AUD) who sought to reduce or stop their drinking. We stratified the randomization on genotype (rs2832407*C-allele homozygotes vs. A-allele carriers) and assigned 170 European-American participants (71.2% male) to receive 12 weeks of treatment with topiramate (N  = 85), at a maximal daily dosage of 200 mg, or matching placebo (N = 85). At each of nine treatment visits participants received brief counseling to reduce drinking and increase abstinent days. We hypothesized that topiramate-treated patients with the rs2832407*CC genotype would reduce heavy drinking days (HDDs) more than the other three groups. The rate of treatment completion was 91.8% in both groups. The mean number of HDDs per week in the placebo group was 1.67 (95% CI = (1.29, 2.16), p = 0.0001) times greater than in the topiramate group, which was confirmed by the topiramate group's significantly greater reduction in the concentration of the liver enzyme γ-glutamyltransferase and lower alcohol-related problems score. There was no significant difference in topiramate's effect on HDDs between genotype groups. Although consistent with other studies showing a reduction in heavy drinking with topiramate treatment, the prior finding of a moderating effect of rs2832407 genotype was not replicated in this prospective trial.

Is the mechanism of action of antiseizure drugs a key element in the choice of treatment?

About 25 antiseizure drugs are available for the treatment of patients with epilepsy. The choice of the most suited drug for a specific patient is primarily based on the results of the pivotal randomized clinical trials and on the patient's characteristics and comorbidities. Whether or not the mechanism of action of the antiseizure drugs should be also taken into account to better predict the patient's response to the treatment remains a matter of debate. Despite the apparent complexity and diversity of antiseizure drug mechanisms of action, the reality unfortunately remains that they are very close, in particular with regard to their relationship with the pathophysiology of epilepsy. With the only exception of the association between lamotrigine and sodium valproate, there are no clinical data that formally support a synergistic association between certain antiseizure drugs in terms of efficacy. However, anticipating risk of adverse events by limiting as far as possible the combination of drugs, which share the same mechanisms of action, is undoubtedly an important driver of daily therapeutic decisions.

The Effect of Anti-seizure Medications on the Propagation of Epileptic Activity: A Review

The propagation of epileptiform events is a highly interesting phenomenon from the pathophysiological point of view, as it involves several mechanisms of recruitment of neural networks. Extensive in vivo and in vitro research has been performed, suggesting that multiple networks as well as cellular candidate mechanisms govern this process, including the co-existence of wave propagation, coupled oscillator dynamics, and more. The clinical importance of seizure propagation stems mainly from the fact that the epileptic manifestations cannot be attributed solely to the activity in the seizure focus itself, but rather to the propagation of epileptic activity to other brain structures. Propagation, especially when causing secondary generalizations, poses a risk to patients due to recurrent falls, traumatic injuries, and poor neurological outcome. Anti-seizure medications (ASMs) affect propagation in diverse ways and with different potencies. Importantly, for drug-resistant patients, targeting seizure propagation may improve the quality of life even without a major reduction in simple focal events. Motivated by the extensive impact of this phenomenon, we sought to review the literature regarding the propagation of epileptic activity and specifically the effect of commonly used ASMs on it. Based on this body of knowledge, we propose a novel classification of ASMs into three main categories: major, minor, and intermediate efficacy in reducing the propagation of epileptiform activity.

Association of preoperative seizures with tumor metabolites quantified by magnetic resonance spectroscopy in gliomas

Seizures are common in patients with gliomas; however, the mechanisms of epileptogenesis in gliomas have not been fully understood. This study hypothesized that analyzing quantified metabolites using magnetic resonance spectroscopy (MRS) might provide novel insights to better understand the epileptogenesis in gliomas, and specific metabolites might be indicators of preoperative seizures in gliomas. We retrospectively investigated patient information (gender, age at diagnosis of tumor, their survival time) and tumor information (location, histology, genetic features, and metabolites according to MRS) in patients with gliomas. The data were correlated with the incidence of seizure and analyzed statistically. Of 146 adult supratentorial gliomas, isocitrate dehydrogenase (IDH) mutant tumors significantly indicated higher incidence of preoperative seizures than IDH wild-type gliomas. However, MRS study indicated that glutamate concentration in IDH wild-type gliomas was higher than that in IDH mutant gliomas. Glutamate was not associated with high frequency of preoperative seizures in patients with gliomas. Instead, increased total N-acetyl-L-aspartate (tNAA) was significantly associated with them. Moreover, multivariable analysis indicated that increased level of tNAA was an independent predictor of preoperative seizures. According to MRS analysis, tNAA, rather than glutamate, might be a useful to detect preoperative seizures in patient with supratentorial gliomas.

The subiculum and its role in focal epileptic disorders

The subicular complex (hereafter referred as subiculum), which is reciprocally connected with the hippocampus and rhinal cortices, exerts a major control on hippocampal outputs. Over the last three decades, several studies have revealed that the subiculum plays a pivotal role in learning and memory but also in pathological conditions such as mesial temporal lobe epilepsy (MTLE). Indeed, subicular networks actively contribute to seizure generation and this structure is relatively spared from the cell loss encountered in this focal epileptic disorder. In this review, we will address: (i) the functional properties of subicular principal cells under normal and pathological conditions; (ii) the subiculum role in sustaining seizures in in vivo models of MTLE and in in vitro models of epileptiform synchronization; (iii) its presumptive role in human MTLE; and (iv) evidence underscoring the relationship between subiculum and antiepileptic drug effects. The studies reviewed here reinforce the view that the subiculum represents a limbic area with relevant, as yet unexplored, roles in focal epilepsy.

Ionotropic Glutamate Receptors in Epilepsy: A Review Focusing on AMPA and NMDA Receptors

It is widely accepted that glutamate-mediated neuronal hyperexcitation plays a causative role in eliciting seizures. Among glutamate receptors, the roles of N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors in physiological and pathological conditions represent major clinical research targets. It is well known that agonists of NMDA or AMPA receptors can elicit seizures in animal or human subjects, while antagonists have been shown to inhibit seizures in animal models, suggesting a potential role for NMDA and AMPA receptor antagonists in anti-seizure drug development. Several such drugs have been evaluated in clinical studies; however, the majority, mainly NMDA-receptor antagonists, failed to demonstrate adequate efficacy and safety for therapeutic use, and only an AMPA-receptor antagonist, perampanel, has been approved for the treatment of some forms of epilepsy. These results suggest that a misunderstanding of the role of each glutamate receptor in the ictogenic process may underlie the failure of these drugs to demonstrate clinical efficacy and safety. Accumulating knowledge of both NMDA and AMPA receptors, including pathological gene mutations, roles in autoimmune epilepsy, and evidence from drug-discovery research and pharmacological studies, may provide valuable information enabling the roles of both receptors in ictogenesis to be reconsidered. This review aimed to integrate information from several studies in order to further elucidate the specific roles of NMDA and AMPA receptors in epilepsy.

Evolving Mechanistic Concepts of Epileptiform Synchronization and their Relevance in Curing Focal Epileptic Disorders

The synchronized activity of neuronal networks under physiological conditions is mirrored by specific oscillatory patterns of the EEG that are associated with different behavioral states and cognitive functions. Excessive synchronization can, however, lead to focal epileptiform activity characterized by interictal and ictal discharges in epileptic patients and animal models. This review focusses on studies that have addressed epileptiform synchronization in temporal lobe regions by employing in vitro and in vivo recording techniques. First, we consider the role of ionotropic and metabotropic excitatory glutamatergic transmission in seizure generation as well as the paradoxical role of GABAA signaling in initiating and perhaps maintaining focal seizure activity. Second, we address non-synaptic mechanisms (which include voltage-gated ionic currents and gap junctions) in the generation of epileptiform synchronization. For each mechanism, we discuss the actions of antiepileptic drugs that are presumably modulating excitatory or inhibitory signaling and voltage-gated currents to prevent seizures in epileptic patients. These findings provide insights into the mechanisms of seizure initiation and maintenance, thus leading to the development of specific pharmacological treatments for focal epileptic disorders.

Pharmacogenetics of alcohol use disorder treatments: an update

Introduction: Alcohol use disorder (AUD) is highly prevalent; costly economically, socially, and interpersonally; and grossly undertreated. The low rate of utilization of medications with demonstrated (albeit modest) efficacy is particularly noteworthy. One approach to increasing the utility and safety of available medications is to use a precision medicine approach, which seeks to identify patients for whom specific medications are likely to be most efficacious and have the fewest adverse effects. Areas Covered: We review the literature on the pharmacogenetics of AUD treatment using both approved and off-label medications. We cover both laboratory studies and clinical trials, highlighting valuable mechanistic insights and underscoring the potential value of precision-based care for AUD. Expert Opinion: Pharmacotherapy can be a useful component of AUD treatment. Currently, the evidence regarding genetic predictors of medication efficacy is very limited. Thus, a precision medicine approach is not yet ready for widespread clinical implementation. Further research is needed to identify candidate genetic variants that moderate the response to both established and novel medications. The growing availability of large-scale, longitudinal datasets that enable the synthesis of genetic and electronic health record data provides important opportunities to develop this area of research.

Guidelines for biological treatment of substance use and related disorders, part 1: Alcoholism, first revision

These practice guidelines for the biological treatment of alcohol use disorders are an update of the first edition, published in 2008, which was developed by an international Task Force of the World Federation of Societies of Biological Psychiatry (WFSBP). For this 2016 revision, we performed a systematic review (MEDLINE/PUBMED database, Cochrane Library) of all available publications pertaining to the biological treatment of alcoholism and extracted data from national guidelines. The Task Force evaluated the identified literature with respect to the strength of evidence for the efficacy of each medication and subsequently categorised it into six levels of evidence (A-F) and five levels of recommendation (1-5). Thus, the current guidelines provide a clinically and scientifically relevant, evidence-based update of our earlier recommendations. These guidelines are intended for use by clinicians and practitioners who evaluate and treat people with alcohol use disorders and are primarily concerned with the biological treatment of adults with such disorders.

Neonatal hypoxic ischemic encephalopathy: an update on disease pathogenesis and treatment

INTRODUCTION

Hypoxic ischemic encephalopathy (HIE) is the most important reason for morbidity and mortality in term-born infants. Understanding pathophysiology of the brain damage is essential for the early detection of patients with high risk for HIE and development of strategies for their treatments. Areas covered: This review discusses pathophysiology of the neonatal HIE and its treatment options, including hypothermia, melatonin, allopurinol, topiramate, erythropoietin, N-acetylcyctein, magnesium sulphate and xenon. Expert commentary: Several clinical studies have been performed in order to decrease the risk of brain injury due to difficulties in the early diagnosis and treatment, and to develop strategies for better long-term outcomes. Although currently standard treatment methods include therapeutic hypothermia for neonates with moderate to severe HIE, new supportive options are needed to enhance neuroprotective effects of the hypothermia, which should aim to reduce production of the free radicals and to have anti-inflammatory and anti-apoptotic actions.

The New Era of Drug Therapy for Obesity: The Evidence and the Expectations

There is an urgent need for effective pharmacological therapies to help tackle the growing obesity epidemic and the healthcare crisis it poses. The past 3 years have seen approval of a number of novel anti-obesity drugs. The majority of these influence hypothalamic appetite pathways via dopaminergic or serotoninergic signalling. Some are combination therapies, allowing lower doses to minimize the potential for off-target effects. An alternative approach is to mimic endogenous satiety signals using long-lasting forms of peripheral appetite-suppressing hormones. There is also considerable interest in targeting thermogenesis by brown adipose tissue to increase resting energy expenditure. Obesity pharmacotherapy has seen several false dawns, but improved understanding of the pathways regulating energy balance, and better-designed trials, give many greater confidence that recently approved agents will be both efficacious and safe. Nevertheless, a number of issues from preclinical and clinical development continue to attract debate, and additional large-scale trials are still required to address areas of uncertainty.

Neuroprotective Strategies after Neonatal Hypoxic Ischemic Encephalopathy

Neonatal hypoxic ischemic encephalopathy (HIE) is a devastating disease that primarily causes neuronal and white matter injury and is among the leading cause of death among infants. Currently there are no well-established treatments; thus, it is important to understand the pathophysiology of the disease and elucidate complications that are creating a gap between basic science and clinical translation. In the development of neuroprotective strategies and translation of experimental results in HIE, there are many limitations and challenges to master based on an appropriate study design, drug delivery properties, dosage, and use in neonates. We will identify understudied targets after HIE, as well as neuroprotective molecules that bring hope to future treatments such as melatonin, topiramate, xenon, interferon-beta, stem cell transplantation. This review will also discuss some of the most recent trials being conducted in the clinical setting and evaluate what directions are needed in the future.

Potent anti-seizure effects of D-leucine

There are no effective treatments for millions of patients with intractable epilepsy. High-fat ketogenic diets may provide significant clinical benefit but are challenging to implement. Low carbohydrate levels appear to be essential for the ketogenic diet to work, but the active ingredients in dietary interventions remain elusive, and a role for ketogenesis has been challenged. A potential antiseizure role of dietary protein or of individual amino acids in the ketogenic diet is understudied. We investigated the two exclusively ketogenic amino acids, L-leucine and L-lysine, and found that only L-leucine potently protects mice when administered prior to the onset of seizures induced by kainic acid injection, but not by inducing ketosis. Unexpectedly, the D-enantiomer of leucine, which is found in trace amounts in the brain, worked as well or better than L-leucine against both kainic acid and 6Hz electroshock-induced seizures. However, unlike L-leucine, D-leucine potently terminated seizures even after the onset of seizure activity. Furthermore, D-leucine, but not L-leucine, reduced long-term potentiation but had no effect on basal synaptic transmission in vitro. In a screen of candidate neuronal receptors, D-leucine failed to compete for binding by cognate ligands, potentially suggesting a novel target. Even at low doses, D-leucine suppressed ongoing seizures at least as effectively as diazepam but without sedative effects. These studies raise the possibility that D-leucine may represent a new class of anti-seizure agents, and that D-leucine may have a previously unknown function in eukaryotes.

GRIK1 genotype and daily expectations of alcohol's positive effects moderate the reduction of heavy drinking by topiramate

Using retrospective reports obtained during treatment visits in 138 heavy drinkers, we found that topiramate's reduction of heavy drinking was moderated by a polymorphism (rs2832407) in GRIK1, which encodes the GluK1 kainate subunit (Kranzler et al., 2014a). A subsequent analysis of that 12-week topiramate treatment trial showed similar effects of medication and genotype on daily drinking reports obtained via interactive voice response technology (IVR; Kranzler et al., 2014b). Specifically, rs2832407*C-allele homozygotes treated with topiramate reported lower levels of drinking than those receiving placebo. This group also had the largest decreases in the expected positive effects of drinking (i.e., expectancies) and desire to drink. To extend that analysis, which focused on how mean levels of desire and expectancies changed over time with treatment, we used a within-person approach to examine whether daily variation in expectancies and desire to drink interact with topiramate treatment and genotype to predict nighttime drinking levels. In contrast to the previous analysis (Kranzler et al., 2014b), here we focus on whether alcohol expectancies and desire to drink moderate the effects of topiramate on drinking. Results showed a 3-way interaction of daily expectancies with genotype and medication, such that the protective effect of topiramate on nighttime drinking among rs2832407*C-allele homozygotes was decreased on days characterized by relatively high levels of anticipated positive effects of alcohol. There was no moderating effect of desire to drink or negative alcohol expectancies. Thus, there is specific moderation of the effects of topiramate by both genotype and cognitive process.

Migraine prophylaxis, ischemic depolarizations, and stroke outcomes in mice

BACKGROUND AND PURPOSE

Migraine with aura is an established stroke risk factor, and excitatory mechanisms such as spreading depression (SD) are implicated in the pathogenesis of both migraine and stroke. Spontaneous SD waves originate within the peri-infarct tissue and exacerbate the metabolic mismatch during focal cerebral ischemia. Genetically enhanced SD susceptibility facilitates anoxic depolarizations and peri-infarct SDs and accelerates infarct growth, suggesting that susceptibility to SD is a critical determinant of vulnerability to ischemic injury. Because chronic treatment with migraine prophylactic drugs suppresses SD susceptibility, we tested whether migraine prophylaxis can also suppress ischemic depolarizations and improve stroke outcome.

METHODS

We measured the cortical susceptibility to SD and ischemic depolarizations, and determined tissue and neurological outcomes after middle cerebral artery occlusion in wild-type and familial hemiplegic migraine type 1 knock-in mice treated with vehicle, topiramate or lamotrigine daily for 7 weeks or as a single dose shortly before testing.

RESULTS

Chronic treatment with topiramate or lamotrigine reduced the susceptibility to KCl-induced or electric stimulation-induced SDs as well as ischemic depolarizations in both wild-type and familial hemiplegic migraine type 1 mutant mice. Consequently, both tissue and neurological outcomes were improved. Notably, treatment with a single dose of either drug was ineffective.

CONCLUSIONS

These data underscore the importance of hyperexcitability as a mechanism for increased stroke risk in migraineurs, and suggest that migraine prophylaxis may not only prevent migraine attacks but also protect migraineurs against ischemic injury.

Topiramate's reduction of body mass index in heavy drinkers: lack of moderation by a GRIK1 polymorphism

Topiramate, which interacts with multiple neurotransmitter and enzyme systems, is approved by the Food and Drug Administration to treat seizure disorder, prevent migraine, and (in combination with phentermine) reduce weight. Topiramate has also been shown in multiple studies to reduce heavy drinking. The authors found that topiramate 200 mg/day significantly reduced heavy drinking in heavy drinkers with a treatment goal of reduced drinking (Kranzler et al., 2014). Further, in the European American (EA) subsample (n = 122), a single nucleotide polymorphism (rs2832407) in GRIK1, which encodes the GluK1 subunit of the kainate receptor, moderated the effect on heavy drinking days. Here the authors examined the effects of topiramate on body mass index (BMI) and the moderating effect of rs2832407 in the EA subsample from Kranzler et al. (2014). Across the 12 weeks of treatment, BMI was reduced by 1.2 kg/m2 (p < .001) in the topiramate group but was unchanged in the placebo group. There was no evidence of moderation by rs2832407 of topiramate's effects on BMI. Controlling for changes in drinking and other potential confounders did not alter the findings. These results suggest that the effect of topiramate on drinking behavior, in which the GluK1-containing kainate receptor appears to play a key role, can be dissociated from its effect on weight, the specific mechanism of which remains to be determined.

GRIK1 genotype moderates topiramate's effects on daily drinking level, expectations of alcohol's positive effects and desire to drink

We (Kranzler et al., 2014) reported that topiramate 200 mg/day reduced heavy drinking days and increased abstinent days in 138 heavy drinkers whose treatment goal was to reduce drinking to safe levels. In that 12-week, placebo-controlled study, we measured drinking using the Timeline Follow-back method at each treatment visit. In addition to the intent-to-treat effects of topiramate, we found that a single nucleotide polymorphism (rs2832407) in GRIK1, encoding the GluK1 subunit of the kainate receptor, moderated the treatment effect in European Americans (EAs; n = 122). Topiramate reduced heavy drinking only in rs2832407*C allele homozygotes. Here, we augment those analyses by using patients' daily reports obtained using interactive voice response technology; (a) to validate the interactive effects of GRIK1 and topiramate as predictors of drinking level; and, (b) to examine changes in expected positive effects of drinking (i.e. positive outcome expectancies) and desire to drink. We found that rs2832407*C allele homozygotes treated with topiramate drank less overall during treatment than those receiving placebo, validating our earlier findings for heavy drinking days (Kranzler et al., 2014). There was also a study day × medication group × genotype group interaction that predicted both positive alcohol expectancies and desire to drink, with rs2832407*C-allele homozygotes treated with topiramate showing the largest decreases in these outcomes during the study period. Changes in positive alcohol expectancies or desire to drink did not mediate the effects on drinking. These findings validate and extend our previous pharmacogenetic findings with topiramate.

Topiramate treatment for heavy drinkers: moderation by a GRIK1 polymorphism

OBJECTIVE

Topiramate has been shown to reduce drinking and heavy drinking in individuals with alcohol dependence whose goal was to stop drinking. The authors evaluated the efficacy and tolerability of topiramate in heavy drinkers whose treatment goal was to reduce drinking to safe levels.

METHOD

A total of 138 individuals (62.3% men) were randomly assigned to receive 12 weeks of treatment with topiramate (N=67), at a maximal daily dose of 200 mg, or matching placebo (N=71). Both groups received brief counseling to reduce drinking and increase abstinent days. It was hypothesized that topiramate-treated patients would be better able to achieve these goals, and it was predicted that based on prior research, the effects would be moderated by a single nucleotide polymorphism (rs2832407) in GRIK1, encoding the kainate GluK1 receptor subunit.

RESULTS

The rate of treatment completion was 84.9% and equal by treatment group. Topiramate treatment significantly reduced heavy drinking days and increased abstinent days relative to placebo. Patients receiving topiramate also had lower concentrations of the liver enzyme γ-glutamyl transpeptidase and lower scores on a measure of alcohol-related problems than the placebo group. In a European American subsample (N=122), topiramate's effect on heavy drinking days was significantly greater than that for placebo only in rs2832407 C-allele homozygotes.

CONCLUSIONS

These findings support the use of topiramate at a daily dose of 200 mg to reduce heavy drinking in problem drinkers. The moderator effect of rs2832407, if validated, would facilitate the identification of heavy drinkers who are likely to respond well to topiramate treatment and provide an important personalized treatment option. The pharmacogenetic findings also implicate the kainate receptor in the mechanism of topiramate's effects on heavy drinking.

Newly emerging therapies for neonatal seizures

The treatment of neonatal seizures has not changed significantly over the last 50 years despite advances in antiepileptic drug (AED) development for older children and adults. Recently new drugs have emerged some of which address age-specific challenges or mechanisms and will be discussed in this review. The loop diuretic bumetanide blocks the neuronal NKCC1 co-transporter and is thought specifically to supress seizures in the immature brain. Levetiracetam has been used in children and infants with good efficacy, an excellent safety profile, and near-ideal pharmacokinetic characteristics. Randomised controlled trials are now underway to test the efficacy of some newer AEDs for neonatal seizures. Topiramate has been shown to have neuroprotective properties in addition to its antiepileptic action and trials in babies with hypoxic-ischaemic encephalopathy are now planned. There is an urgent need to develop age-specific AEDs for preterm and term babies. These drugs must be evaluated with multicentre, collaborative trials using innovative methods and high ethical standards to overcome age-specific challenges with the ultimate aim of improving the outcome for neonates with seizures.

Managing abnormal eating behaviours in frontotemporal lobar degeneration patients with topiramate

Abnormal eating behaviours are specific to frontotemporal lobar degeneration and increase caregiver burden. Topiramate, an anticonvulsant, suppresses cravings for alcohol and other substances and is a potential treatment for binge eating. However, there are few reports on topiramate efficacy for abnormal eating behaviours in frontotemporal lobar degeneration patients. We present three Japanese frontotemporal lobar degeneration patients with abnormal eating behaviours. Topiramate was effective, especially for compulsive eating, in cases with distinct lobar atrophy, but not for all abnormal eating behaviours.

The mTOR inhibitor rapamycin has limited acute anticonvulsant effects in mice

Objective

The mammalian target of rapamycin (mTOR) pathway integrates signals from different nutrient sources, including amino acids and glucose. Compounds that inhibit mTOR kinase activity such as rapamycin and everolimus can suppress seizures in some chronic animal models and in patients with tuberous sclerosis. However, it is not known whether mTOR inhibitors exert acute anticonvulsant effects in addition to their longer term antiepileptogenic effects. To gain insights into how rapamycin suppresses seizures, we investigated the anticonvulsant activity of rapamycin using acute seizure tests in mice.

Methods

Following intraperitoneal injection of rapamycin, normal four-week-old male NIH Swiss mice were evaluated for susceptibility to a battery of acute seizure tests similar to those currently used to screen potential therapeutics by the US NIH Anticonvulsant Screening Program. To assess the short term effects of rapamycin, mice were seizure tested in ≤6 hours of a single dose of rapamycin, and for longer term effects of rapamycin, mice were tested after 3 or more daily doses of rapamycin.

Results

The only seizure test where short-term rapamycin treatment protected mice was against tonic hindlimb extension in the MES threshold test, though this protection waned with longer rapamycin treatment. Longer term rapamycin treatment protected against kainic acid-induced seizure activity, but only at late times after seizure onset. Rapamycin was not protective in the 6 Hz or PTZ seizure tests after short or longer rapamycin treatment times. In contrast to other metabolism-based therapies that protect in acute seizure tests, rapamycin has limited acute anticonvulsant effects in normal mice.

Significance

The efficacy of rapamycin as an acute anticonvulsant agent may be limited. Furthermore, the combined pattern of acute seizure test results places rapamycin in a third category distinct from both fasting and the ketogenic diet, and which is more similar to drugs acting on sodium channels.

Safety and efficacy of topiramate in neonates with hypoxic ischemic encephalopathy treated with hypothermia (NeoNATI)

BACKGROUND

Despite progresses in neonatal care, the mortality and the incidence of neuro-motor disability after perinatal asphyxia have failed to show substantial improvements. In countries with a high level of perinatal care, the incidence of asphyxia responsible for moderate or severe encephalopathy is still 2-3 per 1000 term newborns. Recent trials have demonstrated that moderate hypothermia, started within 6 hours after birth and protracted for 72 hours, can significantly improve survival and reduce neurologic impairment in neonates with hypoxic-ischemic encephalopathy. It is not currently known whether neuroprotective drugs can further improve the beneficial effects of hypothermia. Topiramate has been proven to reduce brain injury in animal models of neonatal hypoxic ischemic encephalopathy. However, the association of mild hypothermia and topiramate treatment has never been studied in human newborns. The objective of this research project is to evaluate, through a multicenter randomized controlled trial, whether the efficacy of moderate hypothermia can be increased by concomitant topiramate treatment.

METHODS/DESIGN

Term newborns (gestational age ≥ 36 weeks and birth weight ≥ 1800 g) with precocious metabolic, clinical and electroencephalographic (EEG) signs of hypoxic-ischemic encephalopathy will be randomized, according to their EEG pattern, to receive topiramate added to standard treatment with moderate hypothermia or standard treatment alone. Topiramate will be administered at 10 mg/kg once a day for the first 3 days of life. Topiramate concentrations will be measured on serial dried blood spots. 64 participants will be recruited in the study. To evaluate the safety of topiramate administration, cardiac and respiratory parameters will be continuously monitored. Blood samplings will be performed to check renal, liver and metabolic balance. To evaluate the efficacy of topiramate, the neurologic outcome of enrolled newborns will be evaluated by serial neurologic and neuroradiologic examinations. Visual function will be evaluated by means of behavioural standardized tests.

DISCUSSION

This pilot study will explore the possible therapeutic role of topiramate in combination with moderate hypothermia. Any favourable results of this research might open new perspectives about the reduction of cerebral damage in asphyxiated newborns.

Presynaptic facilitation of glutamate release in the basolateral amygdala: a mechanism for the anxiogenic and seizurogenic function of GluK1 receptors

Kainate receptors containing the GluK1 subunit (GluK1Rs; previously known as GluR5 kainate receptors) are concentrated in certain brain regions, where they play a prominent role in the regulation of neuronal excitability, by modulating GABAergic and/or glutamatergic synaptic transmission. In the basolateral nucleus of the amygdala (BLA), which plays a central role in anxiety as well as in seizure generation, GluK1Rs modulate GABAergic inhibition via postsynaptic and presynaptic mechanisms. However, the role of these receptors in the regulation of glutamate release, and the net effect of their activation on the excitability of the BLA network are not well understood. Here, we show that in amygdala slices from 35- to 50-day-old rats, the GluK1 agonist (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA) (300 nM) increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) and miniature EPSCs (mEPSCs) recorded from BLA principal neurons, and decreased the rate of failures of evoked EPSCs. The GluK1 antagonist (S)-1-(2-amino-2-carboxyethyl)-3-(2-carboxybenzyl) pyrimidine-2,4-dione (UBP302) (25 or 30 μM) decreased the frequency of mEPSCs, reduced evoked field potentials, and increased the "paired-pulse ratio" of the field potential amplitudes. Taken together, these results suggest that GluK1Rs in the rat BLA are present on presynaptic terminals of principal neurons, where they mediate facilitation of glutamate release. In vivo bilateral microinjections of ATPA (250 pmol) into the rat BLA increased anxiety-like behavior in the open field test, while 2 nmol ATPA induced seizures. Similar intra-BLA injections of UBP302 (20 nmol) had anxiolytic effects in the open field and the acoustic startle response tests, without affecting pre-pulse inhibition. These results suggest that although GluK1Rs in the rat BLA facilitate both GABA and glutamate release, the facilitation of glutamate release prevails, and these receptors can have an anxiogenic and seizurogenic net function. Presynaptic facilitation of glutamate release may, in part, underlie the hyperexcitability-promoting effects of GluK1R activation in the rat BLA.

Topiramate in the treatment of migraine: A kainate (glutamate) receptor antagonist within the trigeminothalamic pathway

Background: The development of new agents for the preventive treatment of migraine is the greatest unmet need in the therapeutics of primary headaches. Topiramate, an anticonvulsant drug, is an effective anti-migraine preventive whose mechanism of action is not fully elucidated. Since glutamate plays a major role in migraine pathophysiology, the potential action of topiramate through glutamatergic mechanisms is of considerable interest.

Methods: Recordings of neurons in the trigeminocervical complex (TCC) and the ventroposteromedial thalamic nucleus (VPM) of anesthetized rats were made using electrophysiological techniques. The effects of intravenous or microiontophorezed topiramate on trigeminovascular activation of second- and third-order neurons in the trigeminothalamic pathway were characterized. The potential interactions of topiramate with the ionotropic glutamate receptors were studied using microiontophoresis.

Results: Both intravenous and microiontophorized topiramate significantly inhibited trigeminovascular activity in the TCC and VPM. In both nuclei microiontophoretic application of topiramate significantly attenuated kainate receptor-evoked firing but had no effect on N-methyl-d-aspartic acid or α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor activation.

Conclusion: The data demonstrate for the first time that topiramate modulates trigeminovascular transmission within the trigeminothalamic pathway with the kainate receptor being a potential target. Understanding the mechanism of action of topiramate may help in the design of new medications for migraine prevention, with the data pointing to glutamate-kainate receptors as a fruitful target to pursue.

Role of kainate receptors in network activity during development

Distinct populations of kainate-type ionotropic glutamate receptors (KARs), located at various cell types and subcellular compartments and utilizing diverse downstream signaling mechanisms, represent an intricate system with large capacity for modulatory effects ranging from synapse-specific changes to alterations in the excitability of large neuronal ensembles. However, the way the diverse functions ascribed for KARs are utilized under different physiological and pathological conditions to regulate activity at the level of neuronal networks is still largely unclear. Here, we address the data regarding functions of KARs in the regulation of network activity in the hippocampus, with a main focus on their roles during early postnatal development. We further discuss the evidence suggesting that KAR mediated signaling during the immature type network activity is involved in the formation and maturation of glutamatergic synapses.

Clinical pharmacology of topiramate in migraine prevention

INTRODUCTION

Migraine is a widespread disorder. Migraine patients experience worse health-related quality of life than the general population. The availability of effective and tolerable treatments for this disorder is an important medical need. This narrative review focuses on the clinical pharmacology of topiramate, an antiepileptic drug that was approved for the prophylaxis of migraine where it should act as a neuromodulator.

AREAS COVERED

A PubMed database search (from 2000 to 24 January 2011) and a review of the human studies published on topiramate and migraine was conducted.

EXPERT OPINION

Topiramate is an important option for the prophylaxis of migraine and is of proven efficacy and tolerability. It has also been studied in chronic migraine with encouraging results, even in patients with medication overuse. However, in migraine prevention its efficacy is comparable to the other first-line drugs and there are no published trials with a superiority design which can establish topiramate's role in the available therapeutic armamentarium.

Glutamatergic medications for the treatment of drug and behavioral addictions

Historically, most pharmacological approaches to the treatment of addictive disorders have utilized either substitution-based methods (i.e., nicotine replacement or opioid maintenance) or have targeted monoaminergic or endogenous opioidergic neurotransmitter systems. However, substantial evidence has accumulated indicating that ligands acting on glutamatergic transmission are also of potential utility in the treatment of drug addiction, as well as various behavioral addictions such as pathological gambling. The purpose of this review is to summarize the pharmacological mechanisms of action and general clinical efficacy of glutamatergic medications that are currently approved or are being investigated for approval for the treatment of addictive disorders. Medications with effects on glutamatergic transmission that will be discussed include acamprosate, N-acetylcysteine, d-cycloserine, gabapentin, lamotrigine, memantine, modafinil, and topiramate. We conclude that manipulation of glutamatergic neurotransmission is a relatively young but promising avenue for the development of improved therapeutic agents for the treatment of drug and behavioral addictions.

Effects of rasagiline, its metabolite aminoindan and selegiline on glutamate receptor mediated signalling in the rat hippocampus slice in vitro

BACKGROUND

Rasagiline, a new drug developed to treat Parkinson's disease, is known to inhibit monoamine oxidase B. However, its metabolite R-(-)-aminoindan does not show this kind of activity. The present series of in vitro experiments using the rat hippocampal slice preparation deals with effects of both compounds on the pyramidal cell response after electric stimulation of the Schaffer Collaterals in comparison to selegiline, another MAO B inhibitor.

METHOD

Stimulation of the Schaffer Collaterals by single stimuli (SS) or theta burst stimulation (TBS) resulted in stable responses of pyramidal cells measured as population spike amplitude (about 1 mV under control SS conditions or about 2 mV after TBS).

RESULTS

During the first series, this response was attenuated in the presence of rasagiline and aminoindan-to a lesser degree of selegiline-in a concentration dependent manner (5-50 μM) after single stimuli as well as under TBS. During oxygen/glucose deprivation for 10 min the amplitude of the population spike breaks down by 75%. The presence of rasagiline and aminoindan, but rarely the presence of selegiline, prevented this break down. Following glutamate receptor mediated enhancements of neuronal transmission in a second series of experiments very clear differences could be observed in comparison to the action of selegiline: NMDA receptor, AMPA receptor as well as metabotropic glutamate receptor mediated increases of transmission were concentration dependently (0,3 - 2 μM) antagonized by rasagiline and aminoindan, but not by selegiline. On the opposite, only selegiline attenuated kainate receptor mediated increases of excitability. Thus, both monoamino oxidase (MAO) B inhibitors show attenuation of glutamatergic transmission in the hippocampus but interfere with different receptor mediated excitatory modulations at low concentrations.

CONCLUSIONS

Since aminoindan does not induce MAO B inhibition, these effects must be regarded as being independent from MAO B inhibition. The results provide strong evidence for a neuroprotective activity of rasagiline and aminoindan in concert with an extended clinical indication into the direction of other diseases like Alzheimer's disease or stroke.

The GluK1 (GluR5) Kainate/{alpha}-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist LY293558 reduces soman-induced seizures and neuropathology

The possibility of mass exposure to nerve agents by a terrorist attack necessitates the availability of antidotes that can be effective against nerve agent toxicity even when administered at a relatively long latency after exposure, because medical assistance may not be immediately available. Nerve agents induce status epilepticus (SE), which can cause brain damage or death. Antagonists of kainate receptors that contain the GluK1 (formerly known as GluR5) subunit (GluK1Rs) are emerging as a new potential treatment for SE and epilepsy from animal research, whereas clinical trials to treat pain have shown that the GluK1/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist LY293558 [(3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl]decahydroisoquinoline-3-carboxylic acid] is safe and well tolerated. Therefore, we tested whether LY293558 is effective against soman-induced seizures and neuropathology, when administered 1 h after soman exposure, in rats. LY293558 stopped seizures induced by soman and reduced the total duration of SE, monitored by electroencephalographic recordings within a 24 h-period after exposure. In addition, LY293558 prevented neuronal loss in the basolateral amygdala (BLA) and the CA1 hippocampal area on both days 1 and 7 after soman exposure and reduced neuronal degeneration in the CA1, CA3, and hilar hippocampal regions, entorhinal cortex, amygdala, and neocortex on day 1 after exposure and in the CA1, CA3, amygdala, and neocortex on day 7 after exposure. It also prevented the delayed loss of glutamic acid decarboxylase-67 immuno-stained BLA interneurons on day 7 after exposure. LY293558 is a potential new emergency treatment for nerve agent exposure that can be expected to be effective against seizures and brain damage even with late administration.

Oral topiramate in neonates with hypoxic ischemic encephalopathy treated with hypothermia: a safety study

OBJECTIVE

To investigate whether topiramate associated with mild or deep hypothermia in asphyxiated term infants is safe in relation to the short-term outcome.

STUDY DESIGN

We report on 27 consecutive asphyxiated newborns who were treated with whole body hypothermia and 27 additional consecutive newborns with hypothermia who were co-treated with oral topiramate, once a day for 3 consecutive days, at 2 different doses.

RESULTS

Newborns were divided in 6 groups according to the depth of hypothermia and the association with higher or lower topiramate dosage. A statistical comparison of the groups identified some differences in biochemical and hemodynamic variables, but no adverse effects attributable to topiramate were detected. There were no statistically significant differences in the groups in short-term outcomes, survival rate at discharge, or incidence of pathologic brain magnetic resonance imaging.

CONCLUSION

Although the number of newborns in this study was limited, the short-term outcome and the safety data appear to support the evaluation of topiramate in clinical trials to explore its possible additive neuroprotective action.