Role of NMDA receptors in the pathophysiology and treatment of status epilepticus

Pyrroloquinoline quinone: a potential neuroprotective compound for neurodegenerative diseases targeting metabolism

Pyrroloquinoline quinone is a quinone described as a cofactor for many bacterial dehydrogenases and is reported to exert an effect on metabolism in mammalian cells/tissues. Pyrroloquinoline quinone is present in the diet being available in foodstuffs, conferring the potential of this compound to be supplemented by dietary administration. Pyrroloquinoline quinone's nutritional role in mammalian health is supported by the extensive deficits in reproduction, growth, and immunity resulting from the dietary absence of pyrroloquinoline quinone, and as such, pyrroloquinoline quinone has been considered as a "new vitamin." Although the classification of pyrroloquinoline quinone as a vitamin needs to be properly established, the wide range of benefits for health provided has been reported in many studies. In this respect, pyrroloquinoline quinone seems to be particularly involved in regulating cell signaling pathways that promote metabolic and mitochondrial processes in many experimental contexts, thus dictating the rationale to consider pyrroloquinoline quinone as a vital compound for mammalian life. Through the regulation of different metabolic mechanisms, pyrroloquinoline quinone may improve clinical deficits where dysfunctional metabolism and mitochondrial activity contribute to induce cell damage and death. Pyrroloquinoline quinone has been demonstrated to have neuroprotective properties in different experimental models of neurodegeneration, although the link between pyrroloquinoline quinone-promoted metabolism and improved neuronal viability in some of such contexts is still to be fully elucidated. Here, we review the general properties of pyrroloquinoline quinone and its capacity to modulate metabolic and mitochondrial mechanisms in physiological contexts. In addition, we analyze the neuroprotective properties of pyrroloquinoline quinone in different neurodegenerative conditions and consider future perspectives for pyrroloquinoline quinone's potential in health and disease.

Brain connectivity analysis in preictal phases of seizure induced by pentylenetetrazol in rats

Abnormal patterns of brain connectivity characterize epilepsy. However, little is known about these patterns during the stages preceding a seizure induced by pentylenetetrazol (PTZ). To investigate brain connectivity in male Wistar rats during the preictal phase of PTZ-induced seizures (60 mg/kg), we recorded local field potentials in the primary motor (M1) cortex, the ventral anterior (VA) nucleus of the thalamus, the hippocampal CA1 area, and the dentate gyrus (DG) during the baseline period and after PTZ administration. While there were no changes in power density between the baseline and preictal periods, we observed an increase in directional functional connectivity in theta from the hippocampal formation to M1 and VA, as well as in middle gamma from DG to CA1 and from CA1 to M1, and also in slow gamma from M1 to CA1. These findings are supported by increased phase coherence between DG-M1 in theta and CA1-M1 in middle gamma, as well as enhanced phase-amplitude coupling of delta-middle gamma in M1 and delta-fast gamma in CA1. Interestingly, we also noted a slight decrease in phase synchrony between CA1 and VA in slow gamma. Together, these results demonstrate increased functional connectivity between brain regions during the PTZ-induced preictal period, with this increase being particularly driven by the hippocampal formation.

The efficacy and safety of ketamine in the treatment of super-refractory status epilepticus: a systematic review

BACKGROUND

Ketamine, as an anesthetic, has been considered for terminating status epilepticus (SE); however, due to the urgency and severity of the condition, there are currently no randomized controlled trials internationally assessing the efficacy of ketamine for treating super-refractory status epilepticus. Similarly, there appears to be a lack of systematic reviews addressing this topic in the literature. Therefore, this systematic review aims to explore the effectiveness and safety of ketamine for terminating super-refractory status epilepticus.

METHODS

We conducted a systematic search on PubMed, EMBASE, and Web of Science databases. Manuscripts unrelated to the research on super-refractory status epilepticus were excluded, as were manuscripts published in non-English languages. The quality assessment and risk of bias were evaluated using the MINORS criteria. Data extraction was limited to qualitative synthesis due to the unsuitability of the data for meta-analysis.

RESULTS

Out of 782 studies retrieved from electronic databases, 11 met the inclusion criteria. Among them, 10 studies were retrospective, and 1 study was prospective. Patient data for inclusion were sourced from the case registries of the researchers' respective hospitals. Across all included studies, the administration of ketamine significantly reduced the duration of status epilepticus and demonstrated higher safety compared to patients not receiving ketamine treatment for super-refractory status epilepticus. Additionally, early administration of ketamine correlated with improved treatment outcomes. The risk of bias across all studies was deemed low.

CONCLUSION

This systematic review suggests that ketamine may be a feasible treatment option for super-refractory status epilepticus. However, given the critical nature of super-refractory status epilepticus, clinicians should prioritize its termination over evaluating the efficacy of specific medications, ensuring patient safety remains paramount. If feasible in real-world medical settings, future research should focus on designing randomized controlled trials to observe the specific efficacy and mechanisms of ketamine. Careful validation is necessary before considering ketamine as a first-line treatment for super-refractory status epilepticus.

Prophylactic treatment with the c-Abl inhibitor, neurotinib, diminishes neuronal damage and the convulsive state in pilocarpine-induced mice

The molecular mechanisms underlying seizure generation remain elusive, yet they are crucial for developing effective treatments for epilepsy. The current study shows that inhibiting c-Abl tyrosine kinase prevents apoptosis, reduces dendritic spine loss, and maintains N-methyl-d-aspartate (NMDA) receptor subunit 2B (NR2B) phosphorylated in in vitro models of excitotoxicity. Pilocarpine-induced status epilepticus (SE) in mice promotes c-Abl phosphorylation, and disrupting c-Abl activity leads to fewer seizures, increases latency toward SE, and improved animal survival. Currently, clinically used c-Abl inhibitors are non-selective and have poor brain penetration. The allosteric c-Abl inhibitor, neurotinib, used here has favorable potency, selectivity, pharmacokinetics, and vastly improved brain penetration. Neurotinib-administered mice have fewer seizures and improved survival following pilocarpine-SE induction. Our findings reveal c-Abl kinase activation as a key factor in ictogenesis and highlight the impact of its inhibition in preventing the insurgence of epileptic-like seizures in rodents and humans.

Animal Venoms as Potential Source of Anticonvulsants

Epilepsy affects millions of people worldwide, and there is an urgent need to develop safe and effective therapeutic agents. Animal venoms contain diverse bioactive compounds like proteins, peptides, and small molecules, which may possess medicinal properties against epilepsy. In recent years, research has shown that venoms from various organisms such as spiders, ants, bees, wasps, and conus snails have anticonvulsant and antiepileptic effects by targeting specific receptors and ion channels. This review underscores the significance of purified proteins and toxins from these sources as potential therapeutic agents for epilepsy. In conclusion, this review emphasizes the valuable role of animal venoms as a natural resource for further exploration in epilepsy treatment research.

The Relationship between Muscarinic and Cannabinoid Receptors in Neuronal Excitability and Epilepsy: A Review

Background

Of the seventy million people who suffer from epilepsy, 40 percent of them become resistant to more than one antiepileptic medication and have a higher chance of death. While the classical definition of epilepsy was due to the imbalance between excitatory glutamatergic and inhibitory γ-aminobutyric acid (GABA)-ergic signalling, substantial evidence implicates muscarinic receptors in the regulation of neural excitability.

Summary

Cannabinoids have shown to reduce seizure activity and neuronal excitability in several epileptic models through the activation of muscarinic receptors with drugs which modulate their activity. Cannabinoids also have been effective in reducing antiepileptic activity in pharmaco-resistant individuals; however, the mechanism of its effects in temporal lobe epilepsy is not clear.

Key Messages

This review seeks to elucidate the relationship between muscarinic and cannabinoid receptors in epilepsy and neural excitability.

Effect of single intravenous injection of esketamine on quality of recovery during early period after modified radical mastectomy for breast cancer: A retrospective study

Objective

To assess the impact of a single esketamine intravenous (IV) injection on the quality of recovery during early period after modified radical mastectomy for breast cancer.

Methods

This retrospective study included 80 patients who underwent modified radical mastectomy under general anesthesia in Huzhou Maternity & Child Health Care Hospital from March to October 2022. All patients were between 35 to 55 years, weighting between 45 and 70 kg and Grade-I or II according to the American Society of Anesthesiologists (ASA). Patients were grouped based on the type of pain management used. Patients (n=40) who were given 0.25 mg/kg esketamine single IV injection prior to completion of the surgery were assigned to Group-E, and patients (n=40) who were not treated with esketamine, comprised the control Group-C. Patients' data, such as education years, operation time, blood loss, the 9-item Quality of Recovery (QoR-9) scores before the anesthesia induction (T0), one (T1) and two hours after the extubation (T2), the 40-item Quality of Recovery (QoR-40) scores one (D1) and two days after the surgery (D2), and the rate of adverse reactions were assessed in both groups.

Results

Compared with T0, the QoR-9 scores at T1 and T2 were markedly lower in all patients. Compared to Group-C, the QoR-9 scores at T1 and T2 in Group-E were considerably increased (P<0.05). Similarly, the QoR-40 scores on D1 and D2 in Group-E were significantly higher compared to Group-C (P

Conclusion

Single intravenous injection of esketamine can improve the quality of the recovery of breast cancer patients during the early period after the modified radical mastectomy.

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Key Words

• Esketamine
• Modified Radical Mastectomy for Breast Cancer
• Quality of Recovery Score

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Affiliation(s)

Guofang Fei Guofang Fei, Department of Anesthesiology, Huzhou Maternity & Child, Health Care Hospital, Huzhou 313000, Zhejiang Province, P.R. China
Wei Yan Wei Yan, Department of Anesthesiology, Huzhou Maternity & Child, Health Care Hospital, Huzhou 313000, Zhejiang Province, P.R. China
Huaqi Yao Huaqi Yao, Department of Anesthesiology, Huzhou Maternity & Child, Health Care Hospital, Huzhou 313000, Zhejiang Province, P.R. China

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The role of molecular chaperones in the mechanisms of epileptogenesis

Epilepsy is a group of neurological diseases which requires significant economic costs for the treatment and care of patients. The central point of epileptogenesis stems from the failure of synaptic signal transmission mechanisms, leading to excessive synchronous excitation of neurons and characteristic epileptic electroencephalogram activity, in typical cases being manifested as seizures and loss of consciousness. The causes of epilepsy are extremely diverse, which is one of the reasons for the complexity of selecting a treatment regimen for each individual case and the high frequency of pharmacoresistant cases. Therefore, the search for new drugs and methods of epilepsy treatment requires an advanced study of the molecular mechanisms of epileptogenesis. In this regard, the investigation of molecular chaperones as potential mediators of epileptogenesis seems promising because the chaperones are involved in the processing and regulation of the activity of many key proteins directly responsible for the generation of abnormal neuronal excitation in epilepsy. In this review, we try to systematize current data on the role of molecular chaperones in epileptogenesis and discuss the prospects for the use of chemical modulators of various chaperone groups' activity as promising antiepileptic drugs.

Why ketamine

We present the rationale for testing ketamine as an add-on therapy for treating benzodiazepine refractory (established) status epilepticus. In animal studies, ketamine terminates benzodiazepine refractory status epilepticus by interfering with the pathophysiological mechanisms and is a neuroprotectant. Ketamine does not suppress respiration when used for sedation and anesthesia. A Series of reports suggest that ketamine can help terminate refractory and super refractory status epilepticus. We propose to use 1 or 3 mg/Kg ketamine intravenously based on animal-to-human conversion and pharmacokinetic studies. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

The value of serum albumin concentration in predicting functional outcome of status epilepticus: An observational study

OBJECTIVE

Status epilepticus (SE) is a common neurological emergency with unsatisfying prognoses, and accurate prediction of functional outcome is beneficial in clinical decision-making. The relationship between serum albumin concentration and outcome of SE patients has yet to be unveiled.

METHODS

Clinical profiles of SE patients admitted to Xiangya Hospital, Central South University, from April 2017 to November 2020, were analyzed retrospectively. Outcomes of SE patients at discharge were divided into two groups based on the modified Rankin Scale (mRS): favorable outcome (mRS: 0-3) and unfavorable outcome (mRS: 4-6).

RESULTS

Fifty-one patients were enrolled. Unfavorable functional outcome at discharge was reported in 60.8% (31/51). Serum albumin concentration at admission and the Encephalitis-NCSE-Diazepam resistance-Image abnormalities-Tracheal intubation (END-IT) score remained independent predictors for functional outcome of SE patients. A lower albumin concentration at admission and higher END-IT score indicated a higher chance of unfavorable outcome for SE patients. The cut-off value of serum albumin to predict unfavorable outcome was 35.2 g/L, with a sensitivity of 67.7% and specificity of 85.0%, and an area under the receiver operating characteristic curve (ROC) of .738 (95% CI: .600-.876, p = .004). The preferable END-IT score with optimal sensitivity (74.2%) and specificity (60%) was 2 and the area under the ROC was .742, with 95% CI of .608-.876 (p = .004).

SIGNIFICANCE

Serum albumin concentration at admission and the END-IT score are two independent predictive factors for short-term outcome of SE patients, moreover, the serum albumin concentration is not inferior to the END-IT score in indicating functional outcome at discharge.

Detect, predict, and prevent acute seizures and status epilepticus

Status epilepticus is one of the most frequent pediatric neurological emergencies. While etiology is often influencing the outcome, more easily modifiable risk factors of outcome include detection of prolonged convulsive seizures and status epilepticus and appropriately dosed and timely applied medication treatment. Unpredictability and delayed or incomplete treatment may at times lead to longer seizures, thereby affecting outcomes. Barriers in the care of acute seizures and status epilepticus include the identification of patients at greatest risk of convulsive status epilepticus, potential stigma, distrust, and uncertainties in acute seizure care, including caregivers, physicians, and patients. Furthermore, unpredictability, detection capability, and identification of acute seizures and status epilepticus, limitations in access to obtaining and maintaining appropriate treatment, and rescue treatment options pose challenges. Additionally, timing and dosing of treatment and related acute management algorithms, potential variations in care due to healthcare and physician culture and preference, and factors related to access, equity, diversity, and inclusion of care. We outline strategies for the identification of patients at risk of acute seizures and status epilepticus, improved status epilepticus detection and prediction, and acute closed-loop treatment and status epilepticus prevention. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

The Roles of Glutamate Receptors and Their Antagonists in Status Epilepticus, Refractory Status Epilepticus, and Super-Refractory Status Epilepticus

Status epilepticus (SE) is a neurological emergency with a high mortality rate. When compared to chronic epilepsy, it is distinguished by the durability of seizures and frequent resistance to benzodiazepine (BZD). The Receptor Trafficking Hypothesis, which suggests that the downregulation of γ-Aminobutyric acid type A (GABAA) receptors, and upregulation of N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors play major roles in the establishment of SE is the most widely accepted hypothesis underlying BZD resistance. NMDA and AMPA are ionotropic glutamate receptor families that have important excitatory roles in the central nervous system (CNS). They are both essential in maintaining the normal function of the brain and are involved in a variety of neuropsychiatric diseases, including epilepsy. Based on animal and human studies, antagonists of NMDA and AMPA receptors have a significant impact in ending SE; albeit most of them are not yet approved to be in clinically therapeutic guidelines, due to their psychomimetic adverse effects. Although there is still a dearth of randomized, prospective research, NMDA antagonists such as ketamine, magnesium sulfate, and the AMPA antagonist, perampanel, are regarded to be reasonable optional adjuvant therapies in controlling SE, refractory SE (RSE) or super-refractory SE (SRSE), though there are still a lack of randomized, prospective studies. This review seeks to summarize and update knowledge on the SE development hypothesis, as well as clinical trials using NMDA and AMPA antagonists in animal and human studies of SE investigations.

Anticonvulsant and antioxidant effects of lamotrigine on pilocarpine-induced status epilepticus in mice

OBJECTIVES

The anticonvulsant and antioxidant effects of lamotrigine on status epilepticus (SE) are incompletely understood. We assessed these effects of lamotrigine on pilocarpine (Pilo)-induced SE in mice.

METHODS

Male C57BL/J6 mice were assigned to three groups: the control group, Pilo (400 mg/kg, s.c.)-induced SE (Pilo group) and lamotrigine (20 mg/kg, i.p.) treated (Pilo/lamotrigine group). The latency to SE of Racine's stage 3 or higher, the mortality rate within 2 h of Pilo administration, and the duration of SE until sacrifice were examined. Nitric oxide (NO), malondialdehyde and glutathione of oxidative stress biomarkers were detected in the hippocampus of the sacrificed animals in the above groups. NO was also detected in the cultured rat hippocampal neurons treated with 4 μM Pilo, Pilo+100 μM lamotrigine (Pilo/lamotrigine) and Pilo/lamotrigine+ N-methyl-D-aspartic acid (NMDA) receptor antagonist (10 μM MK-801, 3 μM ifenprodil) to examine the antioxidant effects of lamotrigine via non-NMDA-related pathways.

RESULTS

lamotrigine prolonged the latency to SE, the SE duration until sacrifice, and decreased the mortality rate in mice with Pilo-induced SE. Lamotrigine also decreased hippocampal concentrations of NO and malondialdehyde and increased the concentrations of glutathione in the SE model. Furthermore, there were significant differences in NO concentrations between groups of cultured rat hippocampal neurons treated with Pilo and Pilo/lamotrigine, and with Pilo/lamotrigine and Pilo/lamotrigine+MK-801.

CONCLUSION

Our findings suggest that lamotrigine exerts anticonvulsant and antioxidant effects on SE, but its antioxidant activity may not be fully exerted via NMDA-related pathways.

Rodent Models of Audiogenic Epilepsy: Genetic Aspects, Advantages, Current Problems and Perspectives

Animal models of epilepsy are of great importance in epileptology. They are used to study the mechanisms of epileptogenesis, and search for new genes and regulatory pathways involved in the development of epilepsy as well as screening new antiepileptic drugs. Today, many methods of modeling epilepsy in animals are used, including electroconvulsive, pharmacological in intact animals, and genetic, with the predisposition for spontaneous or refractory epileptic seizures. Due to the simplicity of manipulation and universality, genetic models of audiogenic epilepsy in rodents stand out among this diversity. We tried to combine data on the genetics of audiogenic epilepsy in rodents, the relevance of various models of audiogenic epilepsy to certain epileptic syndromes in humans, and the advantages of using of rodent strains predisposed to audiogenic epilepsy in current epileptology.

The adverse events of ibogaine in humans: an updated systematic review of the literature (2015-2020)

CONTEXT

Ibogaine is the main alkaloid of the African shrub Tabernanthe iboga. It produces hallucinogenic and psychostimulant effects, but it is currently known for the anti-addictive properties. Despite the potential therapeutic effects, several cases of fatalities and serious adverse events related to ibogaine/noribogaine use can be found in the literature. Most studies consist in case reports or were conducted under non-controlled settings, so causation cannot be clearly established.

OBJECTIVES

To update (2015-2020) the literature on the adverse events and fatalities associated with ibogaine/noribogaine administration.

METHODS

Systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

Eighteen studies were included in the final selection. Highly heterogeneous results were found in terms of kind of product used or the known dosages. The adverse events were classified in acute effects (< 24 h), mainly cardiac (the most common was QTc prolongation), gastrointestinal, neurological, and clinical alterations, and long-lasting effects (> 24 h), mainly persistent cardiac alterations, psychiatric, and neurological signs.

CONCLUSIONS

There is a high need of phase I clinical trials that can describe the safety of different dosages of ibogaine with standardized products. Further research should perform clinical profiling of vulnerable populations, and design effective screening methods and clinical procedures.

Why won't it stop? The dynamics of benzodiazepine resistance in status epilepticus

Status epilepticus is a life-threatening neurological emergency that affects both adults and children. Approximately 36% of episodes of status epilepticus do not respond to the current preferred first-line treatment, benzodiazepines. The proportion of episodes that are refractory to benzodiazepines is higher in low-income and middle-income countries (LMICs) than in high-income countries (HICs). Evidence suggests that longer episodes of status epilepticus alter brain physiology, thereby contributing to the emergence of benzodiazepine resistance. Such changes include alterations in GABA_A receptor function and in the transmembrane gradient for chloride, both of which erode the ability of benzodiazepines to enhance inhibitory synaptic signalling. Often, current management guidelines for status epilepticus do not account for these duration-related changes in pathophysiology, which might differentially impact individuals in LMICs, where the average time taken to reach medical attention is longer than in HICs. In this Perspective article, we aim to combine clinical insights and the latest evidence from basic science to inspire a new, context-specific approach to efficiently managing status epilepticus.

Mice lacking full length Adgrb1 (Bai1) exhibit social deficits, increased seizure susceptibility, and altered brain development

The adhesion G protein-coupled receptor BAI1/ADGRB1 plays an important role in suppressing angiogenesis, mediating phagocytosis, and acting as a brain tumor suppressor. BAI1 is also a critical regulator of dendritic spine and excitatory synapse development and interacts with several autism-relevant proteins. However, little is known about the relationship between altered BAI1 function and clinically relevant phenotypes. Therefore, we studied the effect of reduced expression of full length Bai1 on behavior, seizure susceptibility, and brain morphology in Adgrb1 mutant mice. We compared homozygous (Adgrb1-/-), heterozygous (Adgrb1+/-), and wild-type (WT) littermates using a battery of tests to assess social behavior, anxiety, repetitive behavior, locomotor function, and seizure susceptibility. We found that Adgrb1-/- mice showed significant social behavior deficits and increased vulnerability to seizures. Adgrb1-/- mice also showed delayed growth and reduced brain weight. Furthermore, reduced neuron density and increased apoptosis during brain development were observed in the hippocampus of Adgrb1-/- mice, while levels of astrogliosis and microgliosis were comparable to WT littermates. These results show that reduced levels of full length Bai1 is associated with a broader range of clinically relevant phenotypes than previously reported.

The role of ketamine-induced beta activity in the treatment of refractory status epilepticus. Is the EEG useful to determine responder's rate? A retrospective study

INTRODUCTION

Multiple investigations have been done to evaluate the possible effect of ketamine in the treatment of status epilepticus (SE).

OBJECTIVES

To evaluate the electrographic effect of ketamine on EEG, and its clinical utility following-up refractory and super refractory status epilepticus (SRSE).

METHODS

Retrospective review of 24 patients with SE. Clinical record and Video-electroencephalogram (video-EEG) of all included patients were reviewed. The patients' EEGs were then monitored for any immediate changes after administration of the first dose of ketamine as well as at the time patients would be predicted to have peak serum concentration of ketamine. Patients with cessation of electrographic seizures and no SE recurrence within the same admissions were categorized as "Responders". Statistical differences between qualitative variables were analyzed using chi square test. Differences between median were analyzed by Mann-Whitney U test. Difference between groups were considered significant when p < 0.05.

RESULTS

We identified 24 patients with SE. Twelve out of 24 (50%) had SRSE and 12 out of 24 (50%) had refractory status epilepticus (RSE). The appearance of superimposed beta activity after ketamine was initiated was associated with a higher responder rate (100% versus 33.3% in the responder group versus the non-responder group respectively). Notably, the presence of a burst suppression pattern had no significant association with one group compared to the other (41.6% versus 33.3%, in the responder group vs the non-responder group respectively).

CONCLUSIONS

Background superimposed beta activity induced by ketamine is an early and reliable EEG finding associated with status epilepticus termination.

The Neuroactive Steroid Pregnanolone Glutamate: Anticonvulsant Effect, Metabolites and Its Effect on Neurosteroid Levels in Developing Rat Brains

Pregnanolone glutamate (PA-G) is a neuroactive steroid that has been previously demonstrated to be a potent neuroprotective compound in several biological models in vivo. Our in vitro experiments identified PA-G as an inhibitor of N-methyl-D-aspartate receptors and a potentiator of γ-aminobutyric acid receptors (GABA_ARs). In this study, we addressed the hypothesis that combined GABA_AR potentiation and NMDAR antagonism could afford a potent anticonvulsant effect. Our results demonstrated the strong age-related anticonvulsive effect of PA-G in a model of pentylenetetrazol-induced seizures. PA-G significantly decreased seizure severity in 12-day-old animals, but only after the highest dose in 25-day-old animals. Interestingly, the anticonvulsant effect of PA-G differed both qualitatively and quantitatively from that of zuranolone, an investigational neurosteroid acting as a potent positive allosteric modulator of GABA_ARs. Next, we identified 17-hydroxy-pregnanolone (17-OH-PA) as a major metabolite of PA-G in 12-day-old animals. Finally, the administration of PA-G demonstrated direct modulation of unexpected neurosteroid levels, namely pregnenolone and dehydroepiandrosterone sulfate. These results suggest that compound PA-G might be a pro-drug of 17-OH-PA, a neurosteroid with a promising neuroprotective effect with an unknown mechanism of action that may represent an attractive target for studying perinatal neural diseases.

Transcriptome of the Krushinsky-Molodkina Audiogenic Rat Strain and Identification of Possible Audiogenic Epilepsy-Associated Genes

Audiogenic epilepsy (AE), inherent to several rodent strains is widely studied as a model of generalized convulsive epilepsy. The molecular mechanisms that determine the manifestation of AE are not well understood. In the present work, we compared transcriptomes from the corpora quadrigemina in the midbrain zone, which are crucial for AE development, to identify genes associated with the AE phenotype. Three rat strains without sound exposure were compared: Krushinsky-Molodkina (KM) strain (100% AE-prone); Wistar outbred rat strain (non-AE prone) and “0” strain (partially AE-prone), selected from F2 KM × Wistar hybrids for their lack of AE. The findings showed that the KM strain gene expression profile exhibited a number of characteristics that differed from those of the Wistar and “0” strain profiles. In particular, the KM rats showed increased expression of a number of genes involved in the positive regulation of the MAPK signaling cascade and genes involved in the positive regulation of apoptotic processes. Another characteristic of the KM strain which differed from that of the Wistar and “0” rats was a multi-fold increase in the expression level of the Ttr gene and a significant decrease in the expression of the Msh3 gene. Decreased expression of a number of oxidative phosphorylation-related genes and a few other genes was also identified in the KM strain. Our data confirm the complex multigenic nature of AE inheritance in rodents. A comparison with data obtained from other independently selected AE-prone rodent strains suggests some common causes for the formation of the audiogenic phenotype.

Electrical stimulation in animal models of epilepsy: A review on cellular and electrophysiological aspects

Epilepsy is a debilitating condition, primarily refractory individuals, leading to the search for new efficient therapies. Electrical stimulation is an important method used for years to treat several neurological disorders. Currently, electrical stimulation is used to reduce epileptic crisis in patients and shows promising results. Even though the use of electricity to treat neurological disorders has grown worldwide, there are still many caveats that must be clarified, such as action mechanisms and more efficient stimulation treatment parameters. Thus, this review aimed to explore the comprehension of the main stimulation methods in animal models of epilepsy using rodents to develop new experimental protocols and therapeutic approaches.

Efficacy and Safety of Ketamine in Refractory/Super-refractory Nonconvulsive Status Epilepticus: Single-Center Experience

Refractory/super-refractory nonconvulsive status epilepticus (r/srNCSE) is an acute life-threatening neurocritical entity with significant morbidity. Failure to control SE in its earlier stages leads to multiple molecular alterations in the brain such as downregulation of GABA-A and upregulation of NMDA receptors. Recently ketamine, an NMDA receptor antagonist, has gained increased attention as a therapeutic choice in controlling refractory/super-refractory SE. We aimed to analyze the efficacy and safety profile of ketamine in our center. We retrospectively identified all the patients with nonconvulsive SE who received ketamine during their follow-up in our neurological intensive care unit between 2009 and 2019. Information about demographic, clinical, and laboratory findings; concurrent antiseizure and anesthetic medications; time of initiation, dose and duration of ketamine infusion; any adverse effects and finally prognosis were collected. The effect of day of ketamine initiation and duration of infusion on ketamine efficacy were analyzed statistically. Seven patients (4 males, 3 females; age: 44-86 years) were included in the study. Encephalitis was the most common etiology. Concurrent antiseizure medications varied between 2 and 5. Six patients received midazolam before/during ketamine infusion. Ketamine was initiated 2 to 7 days after the onset of EEG monitoring and lasted 3 to 24 days with a maximum infusion dose ranging between 1 to 5 mg/kg/h. It was definitely effective in 4 patients, and possibly effective in an additional patient. Earlier initiation was correlated with higher efficacy (P = .047). There was a trend toward higher efficacy with longer duration of infusion (P = .285). Overall prognosis was poor with 29% mortality rate. Temporary hepatic failure occurred in 1 patient. Ketamine appears to be a promising drug in r/srNCSE. Earlier and prolonged infusion, as well as combination with benzodiazepines may increase its efficacy. Adverse events are rarely observed.

Neuroprotection by delayed triple therapy following sarin nerve agent insult in the rat

The development of refractory status epilepticus (SE) induced by sarin intoxication presents a therapeutic challenge. In our current research we evaluate the efficacy of a delayed combined triple treatment in ending the abnormal epileptiform seizure activity (ESA) and the ensuing of long-term neuronal insult. SE was induced in male Sprague-Dawley rats by exposure to 1.2LD50 sarin insufficiently treated by atropine and TMB4 (TA) 1 min later. Triple treatment of ketamine, midazolam and valproic acid was administered 30 min or 1 h post exposure and was compared to a delayed single treatment with midazolam alone. Toxicity and electrocorticogram activity were monitored during the first week and behavioral evaluation performed 3 weeks post exposure followed by brain biochemical and immunohistopathological analyses. The addition of both single and triple treatments reduced mortality and enhanced weight recovery compared to the TA-only treated group. The triple treatment also significantly minimized the duration of the ESA, reduced the sarin-induced increase in the neuroinflammatory marker PGE2, the brain damage marker TSPO, decreased the gliosis, astrocytosis and neuronal damage compared to the TA+ midazolam or only TA treated groups. Finally, the triple treatment eliminated the sarin exposed increased open field activity, as well as impairing recognition memory as seen in the other experimental groups. The delayed triple treatment may serve as an efficient therapy, which prevents brain insult propagation following sarin-induced refractory SE, even if treatment is postponed for up to 1 h.

Status Epilepticus-Work-Up and Management in Children

Status epilepticus (SE) is one of the most common neurological emergencies in children and has a mortality of 2 to 4%. Admissions for SE are very resource-consuming, especially in refractory and super-refractory SE. An increasing understanding of the pathophysiology of SE leaves room for improving SE treatment protocols, including medication choice and timing. Selecting the most efficacious medications and giving them in a timely manner may improve outcomes. Benzodiazepines are commonly used as first line and they can be used in the prehospital setting, where most SE episodes begin. The diagnostic work-up should start simultaneously to initial treatment, or as soon as possible, to detect potentially treatable causes of SE. Although most etiologies are recognized after the first evaluation, the detection of more unusual causes may become challenging in selected cases. SE is a life-threatening medical emergency in which prompt and efficacious treatment may improve outcomes. We provide a summary of existing evidence to guide clinical decisions regarding the work-up and treatment of SE in pediatric patients.

Neurologic Toxicities Associated with Tumor Necrosis Factor Inhibitors and Calcineurin Inhibitors

The calcineurin inhibitors cyclosporine and tacrolimus are used for their immunosuppressive effects. Neurotoxic side effects include tremor, paresthesia, and headache. Rarer neurotoxicities include seizure, posterior reversible encephalopathy syndrome, and encephalopathy. Tacrolimus tends to be more neurotoxic than cyclosporine. Management of toxicities associated with calcineurin inhibitors includes dose reduction, switching between calcineurin inhibitors, or switching to a calcineurin-free regimen. Tumor necrosis factor (TNF) inhibitors are used in autoimmune diseases. Management of demyelinating conditions among patients treated with anti-TNF should follow standard of care and withdrawal of the anti-TNF. This drug class should be avoided in patients with a history of demyelinating conditions.

Molecular insights into the role of AMPA receptors in the synaptic plasticity, pathogenesis and treatment of epilepsy: therapeutic potentials of perampanel and antisense oligonucleotide (ASO) technology

Glutamate is considered as the predominant excitatory neurotransmitter in the mammalian central nervous systems (CNS). Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are the main glutamate-gated ionotropic channels that mediate the majority of fast synaptic excitation in the brain. AMPARs are highly dynamic that constitutively move into and out of the postsynaptic membrane. Changes in the postsynaptic number of AMPARs play a key role in controlling synaptic plasticity and also brain functions such as memory formation and forgetting development. Impairments in the regulation of AMPAR function, trafficking, and signaling pathway may also contribute to neuronal hyperexcitability and epileptogenesis process, which offers AMPAR as a potential target for epilepsy therapy. Over the last decade, various types of AMPAR antagonists such as perampanel and talampanel have been developed to treat epilepsy, but they usually show limited efficacy at low doses and produce unwanted cognitive and motor side effects when administered at higher doses. In the present article, the latest findings in the field of molecular mechanisms controlling AMPAR biology, as well as the role of these mechanism dysfunctions in generating epilepsy will be reviewed. Also, a comprehensive summary of recent findings from clinical trials with perampanel, in treating epilepsy, glioma-associated epilepsy and Parkinson's disease is provided. Finally, antisense oligonucleotide therapy as an alternative strategy for the efficient treatment of epilepsy is discussed.

Posible involvement of nitric oxide in anticonvulsant effects of citicoline on pentylenetetrazole and electroshock induced seizures in mice

Cerebroneurovascular trauma is recognized as an important risk factor in the development of seizure and epilepsy. Administration of citicoline in these situations is a conventional therapeutic strategy, which combines neurovascular protection and repair effects. The aim of the present study is clarifying the effect of acute and sub-chronic citicoline administration on pentylenetetrazole (PTZ) and electroshock induced seizures in mice. Besides we examined the probable role of NO and its interaction with citicoline in seizure experiments.

Male mice were received acute and sub-chronic regimens of different doses of citicoline (62.5, 125, 250 and 500 mg/kg) before the intravenous or intraperitoneal PTZ-induced seizures or electroshock. To clarify the probable role of NO, 7-nitroindazole (7-NI) (60 mg/kg) or aminoguanidine (AG) (100 mg/kg) were injected 5 min before citicoline in separate groups.

The results revealed that neither acute nor sub-chronic treatment with citicoline could affect the seizures induced by intravenous or intraperitoneal PTZ, but in electroshock model, citicoline showed anti-epileptic properties. Co-administration of citicoline and selective nitric oxide synthase (NOS) inhibitors amplified the anticonvulsant effect of citicoline.

The current results indicated that citicoline has anticonvulsant effects probably through the inhibition of NO.

Action of antiepileptic drugs on neurons

The recent development of various new antiepileptic drugs (AEDs) has provided a wide range of therapeutic strategies for epilepsy. Information regarding the mechanisms of the action of AEDs is valuable when selecting drugs for individual epilepsy patients. AEDs can be categorized as those acting at the excitatory synapse, at the inhibitory synapse, on the extrasynaptic neuronal membrane, or with multiple or miscellaneous mechanisms of action. We herein briefly summarize and illustrate the action of AEDs on neurons and related findings that are pertinent to the clinical aspect of epileptology.

Pharmacotherapy for Pediatric Convulsive Status Epilepticus

Convulsive status epilepticus (CSE) is one of the most common pediatric neurological emergencies. Ongoing seizure activity is a dynamic process and may be associated with progressive impairment of gamma-aminobutyric acid (GABA)-mediated inhibition due to rapid internalization of GABA_A receptors. Further hyperexcitability may be caused by AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-D-aspartic acid) receptors moving from subsynaptic sites to the synaptic membrane. Receptor trafficking during prolonged seizures may contribute to difficulties treating seizures of longer duration and may provide some of the pathophysiological underpinnings of established and refractory SE (RSE). Simultaneously, a practice change toward more rapid initiation of first-line benzodiazepine (BZD) treatment and faster escalation to second-line non-BZD treatment for established SE is in progress. Early administration of the recommended BZD dose is suggested. For second-line treatment, non-BZD anti-seizure medications (ASMs) include valproate, fosphenytoin, or levetiracetam, among others, and at this point there is no clear evidence that any one of these options is better than the others. If seizures continue after second-line ASMs, RSE is manifested. RSE treatment consists of bolus doses and titration of continuous infusions under continuous electro-encephalography (EEG) guidance until electrographic seizure cessation or burst-suppression. Ultimately, etiological workup and related treatment of CSE, including broad spectrum immunotherapies as clinically indicated, is crucial. A potential therapeutic approach for future studies may entail consideration of interventions that may accelerate diagnosis and treatment of SE, as well as rational and early polytherapy based on synergism between ASMs by utilizing medications targeting different mechanisms of epileptogenesis and epileptogenicity.

Pharmacokinetics and Safety of Esketamine in Chinese Patients Undergoing Painless Gastroscopy in Comparison with Ketamine: A Randomized, Open-Label Clinical Study

Purpose

To assess the pharmacokinetics and safety of pure S-ketamine (esketamine) in Chinese patients undergoing painless gastroscopy and evaluate the potential advantage of esketamine in clinical treatment compared with racemate ketamine hydrochloride injection.

Patients and methods

A randomized, open-label, parallel-controlled, Phase I study was performed with 32 patients undergoing painless gastroscopy. Patients received a single dose of esketamine (0.5 mg/kg) or racemic ketamine (1 mg/kg, esketamine:R-ketamine=1:1), injected in 10 s. Blood samples were collected for pharmacokinetic analysis. The concentrations of esketamine, R-ketamine, S-norketamine, and R-norketamine were measured with a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) method.

Results

After administering a single dose of esketamine and racemate ketamine, the pharmacokinetics parameters of esketamine and S-norketamine are both similar in treatment groups. The clearance of esketamine in two groups was 18.1±3.2 and 18.4±3.4 mL/min•kg, respectively. However, in the ketamine group, esketamine has a larger clearance than R-ketamine (18.4±3.4 mL/min·kg vs 15.8±3.1 mL/min·kg, P<0.001). Further analysis showed that gender did not affect the pharmacokinetics of esketamine and racemate ketamine. Regarding the safety of esketamine and racemate ketamine, no serious adverse events were observed during treatment, and the incidences of adverse events were 75.0% (esketamine) and 87.5% (racemate ketamine). The main adverse reactions were dizziness, agitation, nausea, vomiting, headache, and fatigue. However, compared with racemic ketamine, esketamine offers a shorter recovery time (9 mins vs. 13 mins, P<0.05) and orientation recovery time (11.5 mins vs. 17 mins, P<0.05) after short anesthesia.

Conclusion

Esketamine administration as a single dose of 0.5 mg/kg was generally safe and tolerated in patients undergoing painless gastroscopy. In terms of anesthesia, a relatively small dose of esketamine can be used instead of racemate ketamine for routine treatment without consideration of gender differences.

Succinate accumulation induces mitochondrial reactive oxygen species generation and promotes status epilepticus in the kainic acid rat model

Though succinate accumulation is associated with reactive oxygen species (ROS) production and neuronal injury, which play critical roles in epilepsy, it is unclear whether succinate accumulation contributes to the onset of epilepsy or seizures. We sought to investigate changes in succinate, oxidative stress, and mito-SOX levels, as well as mitophagy and neuronal change, in different status epilepticus (SE) rat models. Our results demonstrate that KA-induced SE was accompanied by increased levels of succinate, oxidative stress, and mito-SOX, as well as mitophagy and neuronal degeneration. The similarly increased levels of succinate, oxidative stress, and mito-SOX were also found in pilocarpine-induced SE. Moreover, the reduction of succinate accumulation by the inhibition of succinate dehydrogenase (SDH), malate/aspartate shuttle (MAS), or purine nucleotide cycle (PNC) served to reduce succinate, oxidative stress, and mito-SOX levels, thereby preventing oxidative stress-related neuronal damage and lessening seizure severity. Interestingly, simulating succinate accumulation with succinic acid dimethyl ester may induce succinate accumulation and increased oxidative stress and mito-SOX levels, as well as behavior and seizures in electroencephalograms similar to those observed in rats exposed to KA. Our results indicate that succinate accumulation may contribute to the increased oxidative stress/mitochondrial ROS levels, neuronal degeneration, and SE induced by KA administration. Furthermore, we found that succinate accumulation was mainly due to the inverse catalysis of SDH from fumarate, which was supplemented by the MAS and PNC pathways. These results reveal new insights into the mechanisms underlying SE and that reducing succinate accumulation may be a clinically useful therapeutic target in SE.

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KA- or pilocarpine-induced SE was accompanied by succinate accumulation.

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Succinate accumulation caused elevated ROS/mito-ROS levels and neuronal injury.

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Inverse catalysis of SDH from fumarate mainly caused succinate accumulation.

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Inhibiting succinate accumulation relieved oxidative stress level, neuronal injury, and seizure.

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Simulating succinate accumulation induced elevated oxidative stress level and seizure.