Seizure reduction in TSC2-mutant mouse model by an mTOR catalytic inhibitor.

OBJECTIVE: Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder caused by autosomal-dominant pathogenic variants in either the TSC1 or TSC2 gene, and it is characterized by hamartomas in multiple organs, such as skin, kidney, lung, and brain. These changes can result in epilepsy, learning disabilities, and behavioral complications, among others. The mechanistic link between TSC and the mechanistic target of the rapamycin (mTOR) pathway is well established, thus mTOR inhibitors can potentially be used to treat the clinical manifestations of the disorder, including epilepsy. METHODS: In this study, we tested the efficacy of a novel mTOR catalytic inhibitor (here named Tool Compound 1 or TC1) previously reported to be more brain-penetrant compared with other mTOR inhibitors. Using a well-characterized hypomorphic Tsc2 mouse model, which displays a translationally relevant seizure phenotype, we tested the efficacy of TC1. RESULTS: Our results show that chronic treatment with this novel mTOR catalytic inhibitor (TC1), which affects both the mTORC1 and mTORC2 signaling complexes, reduces seizure burden, and extends the survival of Tsc2 hypomorphic mice, restoring species typical weight gain over development. INTERPRETATION: Novel mTOR catalytic inhibitor TC1 exhibits a promising therapeutic option in the treatment of TSC.

Genomic Index of Sensitivity to Chemotherapy for Triple Negative Breast Cancer.

OBJECTIVE: Patients with triple-negative breast cancer (TNBC) frequently develop resistance to chemotherapy. Studies have shown that microRNAs (miRNAs) are often aberrantly expressed in TNBC and are associated with drug resistance. However, a prognostic strategy that correlates miRNAs with chemotherapy resistance remains largely unknown. METHODS: To identify breast cancer chemoresistance-associated miRNAs, the miRNA microarray dataset GSE71142 was downloaded from the Gene Expression Omnibus database. Differentially expressed miRNAs (DE-miRNAs) in chemoresistant groups were identified using the LIMMA package in R. Potential target genes were predicted using the miRTarBase 9. Functional and pathway enrichment analyses was done using WebGestalt. A protein-protein interaction network was visualized using Cytoscape software. The top six hub genes regulated by DE-miRNAs were identified using the random forest model. The chemotherapy resistance index (CRI) in TNBC was defined as sum of the median expression levels of the top six hub genes. The association of CRI with distant relapse risk was evaluated using point-biserial correlation coefficient in the validation cohorts of patients with TNBC. The correlation between CRI and cumulative hazard rate was estimated using the Cox model, and the predicted rate of distant relapse was obtained from the Breslow-type estimator of the survival function. All statistical computations were performed using Origin2019b. RESULTS: A total of 12 DE-miRNAs were screened, including six upregulated and six downregulated miRNAs in chemoresistant breast cancer tissues compared with chemosensitive tissues. Based on fold changes, miR-214-3p, miR-4758-3p, miR-200c-3p, miR-4254, miR-140-3p, and miR-24-3p were the top six most upregulated miRNAs, whereas miR-142-5p, miR-146-5p, miR-1268b, miR-1275, miR-4447, and miR-4472 were the top six most downregulated miRNAs. The top three hub genes for upregulated miRNAs were RAC1, MYC, and CCND1 and for downregulated miRNAs were IL-6, SOCS1, and PDGFRA. CRI was significantly associated with the risk of distant relapse. CONCLUSION: CRI predicted survival benefits with reduced hazard rate.

N-acetylcysteine treatment mitigates loss of cortical parvalbumin-positive interneuron and perineuronal net integrity resulting from persistent oxidative stress in a rat TBI model.

Traumatic brain injury (TBI) increases cerebral reactive oxygen species production, which leads to continuing secondary neuronal injury after the initial insult. Cortical parvalbumin-positive interneurons (PVIs; neurons responsible for maintaining cortical inhibitory tone) are particularly vulnerable to oxidative stress and are thus disproportionately affected by TBI. Systemic N-acetylcysteine (NAC) treatment may restore cerebral glutathione equilibrium, thus preventing post-traumatic cortical PVI loss. We therefore tested whether weeks-long post-traumatic NAC treatment mitigates cortical oxidative stress, and whether such treatment preserves PVI counts and related markers of PVI integrity and prevents pathologic electroencephalographic (EEG) changes, 3 and 6 weeks after fluid percussion injury in rats. We find that moderate TBI results in persistent oxidative stress for at least 6 weeks after injury and leads to the loss of PVIs and the perineuronal net (PNN) that surrounds them as well as of per-cell parvalbumin expression. Prolonged post-TBI NAC treatment normalizes the cortical redox state, mitigates PVI and PNN loss, and - in surviving PVIs - increases per-cell parvalbumin expression. NAC treatment also preserves normal spectral EEG measures after TBI. We cautiously conclude that weeks-long NAC treatment after TBI may be a practical and well-tolerated treatment strategy to preserve cortical inhibitory tone post-TBI.

Factors influencing the acute pentylenetetrazole-induced seizure paradigm and a literature review.

OBJECTIVE: To confirm the critical factors affecting seizure susceptibility in acute pentylenetetrazole (PTZ) mouse epilepsy models and evaluate the prior literature for these factors. METHODS: Serial cohorts of wild-type mice administered intraperitoneal (IP)-PTZ were aggregated and analyzed by multivariate logistic regression for the effect of sex, age, background strain, dose, and physiologic stress (i.e., EEG implantation and/or single-housing) on seizure response. We assessed the reporting of these factors in a comprehensive literature review over the last 10 years (2010-2020). RESULTS: We conducted aggregated analysis of pooled data of 307 mice (220 C57BL/6J mice and 87 mixed background mice; 202 males, 105 females) with median age of 10 weeks (range: 6-49 weeks) with acute PTZ injection (dose range 40-65 mg/kg). Significance in multivariate analysis was found between seizures and increased PTZ dose (odds ratio (OR) 1.149, 95% confidence interval (CI) 1.102-1.205), older age (OR 1.1, 95% CI 1.041-1.170), physiologic stress (OR 17.36, 95% CI 7.349-44.48), and mixed background strain (OR 0.4725, 95% CI 0.2315-0.9345). Literature review identified 97 papers using acute PTZ-seizure models. Age, housing, sex, and background were omitted by 61% (59/97), 51% (49/97), 18% (17/97), and 8% (8/97) papers, respectively. Only 17% of publications specified all four factors (16/97). INTERPRETATION: Our analysis and literature review demonstrate a critical gap in standardization of acute PTZ-induced seizure paradigm in mice. We recommend that future studies specify and control for age, background strain, sex, and housing conditions of experimental animals.

EEG markers predictive of epilepsy risk in pediatric cerebral malaria - A feasibility study.

OBJECTIVE: Cerebral malaria (CM) affects 500,000 million children annually, 10% whom develop epilepsy within two years. Acute identification of biomarkers for post-CM epilepsy would allow for follow-up of the highest risk populations in resource-limited regions. We investigated the utility of electroencephalogram (EEG) and clinical metrics obtained during acute CM infection for predicting epilepsy. METHODS: We analyzed 70 EEGs recorded within 24 h of admission for CM hospitalization obtained during the Blantyre Malaria Project Epilepsy Study (2005-2007), a prospective cohort study of pediatric CM survivors. While all studies underwent spectral analyses for comparisons of mean power band frequencies, a subset of EEGs from the 10 subjects who developed epilepsy and 10 age- and sex-matched controls underwent conventional visual analysis. Findings were tested for relationships to epilepsy outcomes. RESULTS: Ten of the 70 subjects developed epilepsy. There were no significant differences between groups that were analyzed via visual EEG review; however, spectral EEG analyses revealed a significantly higher gamma-delta power ratio in CM survivors who developed epilepsy (0.23 ±â€¯0.10) than in those who did not (0.16 ±â€¯0.06), p = 0.003. Excluding potential confounders, multivariable logistic-regression analyses found relative gamma power (p = 0.003) and maximum temperature during admission (p = 0.03) significant and independent predictors of post-CM epilepsy, with area under receiver operating characteristics (AUROC) curve of 0.854. CONCLUSIONS: We found that clinical and EEG metrics acquired during acute CM presentation confer risk of post-CM epilepsy. Further studies are required to investigate the utility of gamma activity as a potential biomarker of epileptogenesis and study this process over time. Additionally, resource limitations currently prevent follow-up of all CM cases to surveil for epilepsy, and identification of acute biomarkers in this population would offer the opportunity to allocate resources more efficiently.

Increase in Seizure Susceptibility After Repetitive Concussion Results from Oxidative Stress, Parvalbumin-Positive Interneuron Dysfunction and Biphasic Increases in Glutamate/GABA Ratio.

Chronic symptoms indicating excess cortical excitability follow mild traumatic brain injury, particularly repetitive mild traumatic brain injury (rmTBI). Yet mechanisms underlying post-traumatic excitation/inhibition (E/I) ratio abnormalities may differ between the early and late post-traumatic phases. We therefore measured seizure threshold and cortical gamma-aminobutyric acid (GABA) and glutamate (Glu) concentrations, 1 and 6 weeks after rmTBI in mice. We also analyzed the structure of parvalbumin-positive interneurons (PVIs), their perineuronal nets (PNNs), and their electroencephalography (EEG) signature (gamma frequency band power). For mechanistic insight, we measured cortical oxidative stress, reflected in the reduced/oxidized glutathione (GSH/GSSG) ratio. We found that seizure susceptibility increased both early and late after rmTBI. However, whereas increased Glu dominated the E/I 1 week after rmTBI, Glu concentration normalized and the E/I was instead characterized by depressed GABA, reduced per-PVI parvalbumin expression, and reduced gamma EEG power at the 6-week post-rmTBI time point. Oxidative stress was increased early after rmTBI, where transient PNN degradation was noted, and progressed throughout the monitoring period. We conclude that GSH depletion, perhaps triggered by early Glu-mediated excitotoxicity, leads to late post-rmTBI loss of PVI-dependent cortical inhibitory tone. We thus propose dampening of Glu signaling, maintenance of redox state, and preservation of PVI inhibitory capacity as therapeutic targets for post-rmTBI treatment.

Drug-Responsive Inhomogeneous Cortical Modulation by Direct Current Stimulation.

OBJECTIVE: Cathodal direct current stimulation (cDCS) induces long-term depression (LTD)-like reduction of cortical excitability (DCS-LTD), which has been tested in the treatment of epilepsy with modest effects. In part, this may be due to variable cortical neuron orientation relative to the electric field. We tested, in vivo and in vitro, whether DCS-LTD occurs throughout the cortical thickness, and if not, then whether drug-DCS pairing can enhance the uniformity of the cortical response and the cDCS antiepileptic effect. METHODS: cDCS-mediated changes in cortical excitability were measured in vitro in mouse motor cortex (M1) and in human postoperative neocortex, in vivo in mouse somatosensory cortex (S1), and in a mouse kainic acid (KA)-seizure model. Contributions of N-methyl-D-aspartate-type glutamate receptors (NMDARs) to cDCS-mediated plasticity were tested with application of NMDAR blockers (memantine/D-AP5). RESULTS: cDCS reliably induced DCS-LTD in superficial cortical layers, and a long-term potentiation (LTP)-like enhancement (DCS-LTP) was recorded in deep cortical layers. Immunostaining confirmed layer-specific increase of phospho-S6 ribosomal protein in mouse M1. Similar nonuniform cDCS aftereffects on cortical excitability were also found in human neocortex in vitro and in S1 of alert mice in vivo. Application of memantine/D-AP5 either produced a more uniform DCS-LTD throughout the cortical thickness or at least abolished DCS-LTP. Moreover, a combination of memantine and cDCS suppressed KA-induced seizures. INTERPRETATION: cDCS aftereffects are not uniform throughout cortical layers, which may explain the incomplete cDCS clinical efficacy. NMDAR antagonists may augment cDCS efficacy in epilepsy and other disorders where regional depression of cortical excitability is desirable. ANN NEUROL 2020;88:489-502.

Transcranial magnetic stimulation tracks subminute changes in cortical excitability during propofol anesthesia.

Automated anesthesia systems that continuously monitor cortical excitability (CE) changes to govern drug infusion rates, are desirable. Paired-pulse transcranial magnetic stimulation (ppTMS), with electromyography (EMG), provides noninvasive CE measures. We tested whether, and with what temporal resolution, ppTMS-EMG detects dose-dependent CE in rats anesthetized with continuous intravenous propofol. Motor-evoked potentials (MEPs) were recorded every 20 seconds as either propofol bolus or change in infusion rate was applied. ppTMS-derived measures varied in direct proportion to propofol dose with subminute temporal resolution. We conclude that ppTMS-EMG enables real-time markers of target engagement by anesthetics that may be incorporated into an automated device.

Regulation of lifespan by neural excitation and REST.

The mechanisms that extend lifespan in humans are poorly understood. Here we show that extended longevity in humans is associated with a distinct transcriptome signature in the cerebral cortex that is characterized by downregulation of genes related to neural excitation and synaptic function. In Caenorhabditis elegans, neural excitation increases with age and inhibition of excitation globally, or in glutamatergic or cholinergic neurons, increases longevity. Furthermore, longevity is dynamically regulated by the excitatory-inhibitory balance of neural circuits. The transcription factor REST is upregulated in humans with extended longevity and represses excitation-related genes. Notably, REST-deficient mice exhibit increased cortical activity and neuronal excitability during ageing. Similarly, loss-of-function mutations in the C. elegans REST orthologue genes spr-3 and spr-4 elevate neural excitation and reduce the lifespan of long-lived daf-2 mutants. In wild-type worms, overexpression of spr-4 suppresses excitation and extends lifespan. REST, SPR-3, SPR-4 and reduced excitation activate the longevity-associated transcription factors FOXO1 and DAF-16 in mammals and worms, respectively. These findings reveal a conserved mechanism of ageing that is mediated by neural circuit activity and regulated by REST.

Electrographic spikes are common in wildtype mice.

High-voltage rhythmic electroencephalographic (EEG) spikes have been recorded in wildtype (WT) rats during periods of light slow-wave sleep and passive wakefulness. The source of this activity is unclear but has been attributed to either an inherent form of absence epilepsy or a normal feature of rodent sleep EEG. In contrast, little is known about epileptiform spikes in WT mice. We thus characterize and quantify epileptiform discharges in WT mice for the first time. Thirty-six male WT C57 mice with 24-h wireless telemetry video-EEG recordings were manually scored by blinded reviewers to mark individual spikes and spike trains. Epileptiform spikes were detected in 100% of the recorded WT mice, and spike trains of at least three spikes were recorded in 90% of mice. The spikes were more frequent during the day than at night and were inversely correlated to each animal's locomotor activity. However, the discharges were not absent during active nighttime periods. These discharges may indicate a baseline tendency toward epileptic seizures or perhaps are benign variants of normal rodent background EEG. Nevertheless, a better understanding of baseline WT EEG activity will aid in differentiating pathological and normal EEG activity in mouse epilepsy models.

Succinic semialdehyde dehydrogenase deficiency, a disorder of GABA metabolism: an update on pharmacological and enzyme-replacement therapeutic strategies.

We present an update to the status of research on succinic semialdehyde dehydrogenase (SSADH) deficiency (SSADHD), a rare disorder of GABA metabolism. This is an unusual disorder featuring the accumulation of both GABA and its neuromodulatory analog, gamma-hydroxybutyric acid (GHB), and recent studies have advanced the potential clinical application of NCS-382, a putative GHB receptor antagonist. Animal studies have provided proof-of-concept that enzyme replacement therapy could represent a long-term therapeutic option. The characterization of neuronal stem cells (NSCs) derived from aldehyde dehydrogenase 5a1-/- (aldh5a1-/-) mice, the murine model of SSADHD, has highlighted NSC utility as an in vitro system in which to study therapeutics and associated toxicological properties. Gene expression analyses have revealed that transcripts encoding GABAA receptors are down-regulated and may remain largely immature in aldh5a1-/- brain, characterized by excitatory as opposed to inhibitory outputs, the latter being the expected action in the mature central nervous system. This indicates that agents altering chloride channel activity may be therapeutically relevant in SSADHD. The most recent therapeutic prospects include mTOR (mechanistic target of rapamycin) inhibitors, drugs that have received attention with the elucidation of the effects of elevated GABA on autophagy. The outlook for novel therapeutic trials in SSADHD continues to improve.

mGluR5 Modulation of Behavioral and Epileptic Phenotypes in a Mouse Model of Tuberous Sclerosis Complex.

Drugs targeting metabotropic glutamate receptor 5 (mGluR5) have therapeutic potential in autism spectrum disorders (ASD), including tuberous sclerosis complex (TSC). The question whether inhibition or potentiation of mGluR5 could be beneficial depends, among other factors, on the specific indication. To facilitate the development of mGluR5 treatment strategies, we tested the therapeutic utility of mGluR5 negative and positive allosteric modulators (an mGluR5 NAM and PAM) for TSC, using a mutant mouse model with neuronal loss of Tsc2 that demonstrates disease-related phenotypes, including behavioral symptoms of ASD and epilepsy. This model uniquely enables the in vivo characterization and rescue of the electrographic seizures associated with TSC. We demonstrate that inhibition of mGluR5 corrects hyperactivity, seizures, and elevated de novo synaptic protein synthesis. Conversely, positive allosteric modulation of mGluR5 results in the exacerbation of hyperactivity and epileptic phenotypes. The data suggest a meaningful therapeutic potential for mGluR5 NAMs in TSC, which warrants clinical exploration and the continued development of mGluR5 therapies.

A mouse model of DEPDC5-related epilepsy: Neuronal loss of Depdc5 causes dysplastic and ectopic neurons, increased mTOR signaling, and seizure susceptibility.

DEPDC5 is a newly identified epilepsy-related gene implicated in focal epilepsy, brain malformations, and Sudden Unexplained Death in Epilepsy (SUDEP). In vitro, DEPDC5 negatively regulates amino acid sensing by the mTOR complex 1 (mTORC1) pathway, but the role of DEPDC5 in neurodevelopment and epilepsy has not been described. No animal model of DEPDC5-related epilepsy has recapitulated the neurological phenotypes seen in patients, and germline knockout rodent models are embryonic lethal. Here, we establish a neuron-specific Depdc5 conditional knockout mouse by cre-recombination under the Synapsin1 promotor. Depdc5flox/flox-Syn1Cre (Depdc5cc+) mice survive to adulthood with a progressive neurologic phenotype that includes motor abnormalities (i.e., hind limb clasping) and reduced survival compared to littermate control mice. Depdc5cc+ mice have larger brains with increased cortical neuron size and dysplastic neurons throughout the cortex, comparable to the abnormal neurons seen in human focal cortical dysplasia specimens. Depdc5 results in constitutive mTORC1 hyperactivation exclusively in neurons as measured by the increased phosphorylation of the downstream ribosomal protein S6. Despite a lack of increased mTORC1 signaling within astrocytes, Depdc5cc+ brains show reactive astrogliosis. We observed two Depdc5cc+ mice to have spontaneous seizures, including a terminal seizure. We demonstrate that as a group Depdc5cc+ mice have lowered seizure thresholds, as evidenced by decreased latency to seizures after chemoconvulsant injection and increased mortality from pentylenetetrazole-induced seizures. In summary, our neuron-specific Depdc5 knockout mouse model recapitulates clinical, pathological, and biochemical features of human DEPDC5-related epilepsy and brain malformations. We thereby present an important model in which to study targeted therapeutic strategies for DEPDC5-related conditions.

Replicable in vivo physiological and behavioral phenotypes of the Shank3B null mutant mouse model of autism.

BACKGROUND: Autism spectrum disorder (ASD) is a clinically and biologically heterogeneous condition characterized by social, repetitive, and sensory behavioral abnormalities. No treatments are approved for the core diagnostic symptoms of ASD. To enable the earliest stages of therapeutic discovery and development for ASD, robust and reproducible behavioral phenotypes and biological markers are essential to establish in preclinical animal models. The goal of this study was to identify electroencephalographic (EEG) and behavioral phenotypes that are replicable between independent cohorts in a mouse model of ASD. The larger goal of our strategy is to empower the preclinical biomedical ASD research field by generating robust and reproducible behavioral and physiological phenotypes in animal models of ASD, for the characterization of mechanistic underpinnings of ASD-relevant phenotypes, and to ensure reliability for the discovery of novel therapeutics. Genetic disruption of the SHANK3 gene, a scaffolding protein involved in the stability of the postsynaptic density in excitatory synapses, is thought to be responsible for a relatively large number of cases of ASD. Therefore, we have thoroughly characterized the robustness of ASD-relevant behavioral phenotypes in two cohorts, and for the first time quantified translational EEG activity in Shank3B null mutant mice. METHODS: In vivo physiology and behavioral assays were conducted in two independently bred and tested full cohorts of Shank3B null mutant (Shank3B KO) and wildtype littermate control (WT) mice. EEG was recorded via wireless implanted telemeters for 7 days of baseline followed by 20 min of recording following pentylenetetrazol (PTZ) challenge. Behaviors relevant to the diagnostic and associated symptoms of ASD were tested on a battery of established behavioral tests. Assays were designed to reproduce and expand on the original behavioral characterization of Shank3B KO mice. Two or more corroborative tests were conducted within each behavioral domain, including social, repetitive, cognitive, anxiety-related, sensory, and motor categories of assays. RESULTS: Relative to WT mice, Shank3B KO mice displayed a dramatic resistance to PTZ seizure induction and an enhancement of gamma band oscillatory EEG activity indicative of enhanced inhibitory tone. These findings replicated in two separate cohorts. Behaviorally, Shank3B KO mice exhibited repetitive grooming, deficits in aspects of reciprocal social interactions and vocalizations, and reduced open field activity, as well as variable deficits in sensory responses, anxiety-related behaviors, learning and memory. CONCLUSIONS: Robust animal models and quantitative, replicable biomarkers of neural dysfunction are needed to decrease risk and enable successful drug discovery and development for ASD and other neurodevelopmental disorders. Complementary to the replicated behavioral phenotypes of the Shank3B mutant mouse is the new identification of a robust, translational in vivo neurophysiological phenotype. Our findings provide strong evidence for robustness and replicability of key translational phenotypes in Shank3B mutant mice and support the usefulness of this mouse model of ASD for therapeutic discovery.

Transcranial Magnetic and Direct Current Stimulation in Children.

Promising results in adult neurologic and psychiatric disorders are driving active research into transcranial brain stimulation techniques, particularly transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), in childhood and adolescent syndromes. TMS has realistic utility as an experimental tool tested in a range of pediatric neuropathologies such as perinatal stroke, depression, Tourette syndrome, and autism spectrum disorder (ASD). tDCS has also been tested as a treatment for a number of pediatric neurologic conditions, including ASD, attention-deficit/hyperactivity disorder, epilepsy, and cerebral palsy. Here, we complement recent reviews with an update of published TMS and tDCS results in children, and discuss developmental neuroscience considerations that should inform pediatric transcranial stimulation.

Correction: Microarray Noninvasive Neuronal Seizure Recordings from Intact Larval Zebrafish.

[This corrects the article DOI: 10.1371/journal.pone.0156498.].

Bursts of high-frequency repetitive transcranial magnetic stimulation (rTMS), together with lorazepam, suppress seizures in a rat kainate status epilepticus model.

BACKGROUND: Status epilepticus (SE) is a condition of prolonged or recurrent and often drug-resistant seizures where nonsedating SE therapy remains an important unmet need. Repetitive transcranial magnetic stimulation (rTMS) is emerging as a means to suppress seizures but has not been extensively studied in models. OBJECTIVES: We aimed to test the antiepileptic potential of high-frequency rTMS in SE. As a step toward eventual coupling of rTMS with antiepileptic pharmacotherapy, we also tested whether high-frequency rTMS in combination with a low (ineffective but less likely to cause a side effect) lorazepam dose is as effective as a full lorazepam dose in suppressing seizures in a rat SE model. METHODS: EEG was recorded to measure epileptic spike frequency in the rat kainate SE model. Epileptic spikes were counted before, during, and after either high-frequency rTMS treatment alone or high-frequency rTMS treatment in combination with lorazepam, a firstline SE treatment. RESULTS: We found that rTMS alone decreases epileptic spike frequency only acutely. However, combinatory treatment with half-dose lorazepam together with rTMS was as effective as a full lorazepam dose. CONCLUSION: We report that high-frequency rTMS has modest antiepileptic potential alone but acts in complement with lorazepam to suppress seizures.

Microarray Noninvasive Neuronal Seizure Recordings from Intact Larval Zebrafish.

Zebrafish epilepsy models are emerging tools in experimental epilepsy. Zebrafish larvae, in particular, are advantageous because they can be easily genetically altered and used for developmental and drug studies since agents applied to the bath penetrate the organism easily. Methods for electrophysiological recordings in zebrafish are new and evolving. We present a novel multi-electrode array method to non-invasively record electrical activity from up to 61 locations of an intact larval zebrafish head. This method enables transcranial noninvasive recording of extracellular field potentials (which include multi-unit activity and EEG) to identify epileptic seizures. To record from the brains of zebrafish larvae, the dorsum of the head of an intact larva was secured onto a multi-electrode array. We recorded from individual electrodes for at least three hours and quantified neuronal firing frequency, spike patterns (continuous or bursting), and synchrony of neuronal firing. Following 15 mM potassium chloride- or pentylenetetrazole-infusion into the bath, spike and burst rate increased significantly. Additionally, synchrony of neuronal firing across channels, a hallmark of epileptic seizures, also increased. Notably, the fish survived the experiment. This non-invasive method complements present invasive zebrafish neurophysiological techniques: it affords the advantages of high spatial and temporal resolution, a capacity to measure multiregional activity and neuronal synchrony in seizures, and fish survival for future experiments, such as studies of epileptogenesis and development.

Acute seizure suppression by transcranial direct current stimulation in rats.

OBJECTIVE: Cathodal transcranial direct current stimulation (tDCS) is a focal neuromodulation technique that suppresses cortical excitability by low-amplitude constant electrical current, and may have an antiepileptic effect. Yet, tDCS has not been tested in status epilepticus (SE). Furthermore, a combined tDCS and pharmacotherapy antiseizure approach is unexplored. We therefore examined in the rat pentylenetetrazol (PTZ) SE model whether cathodal tDCS (1) suppresses seizures, (2) augments lorazepam (LZP) efficacy, and (3) enhances GABAergic cortical inhibition. METHODS: Experiment 1 aimed to identify an effective cathodal tDCS intensity. Rats received intraperitoneal PTZ followed by tDCS (sham, cathodal 1 mA, or cathodal 0.1 mA; for 20 min), and then a second PTZ challenge. In Experiment 2, two additional animal groups received a subtherapeutic LZP dose after PTZ, and then verum or sham tDCS. Clinical and electroencephalography (EEG) epileptic activity were compared between all groups. In Experiment 3, we measured GABA-mediated paired-pulse inhibition of the motor evoked potential by paired-pulse transcranial magnetic stimulation (ppTMS) in rats that received PTZ or saline, and either verum or sham tDCS. RESULTS: Cathodal 1 mA tDCS (1) reduced EEG spike bursts, and suppressed clinical seizures after the second PTZ challenge, (2) in combination with LZP was more effective in seizure suppression and improved the clinical seizure outcomes compared to either tDCS or LZP alone, and (3) prevented the loss of ppTMS motor cortex inhibition that accompanied PTZ injection. INTERPRETATION: These results suggest that cathodal 1 mA tDCS alone and in combination with LZP can suppress seizures by augmenting GABAergic cortical inhibition.