Biology subjects

Wilcox, K. S.

Publications and source records attributed to Wilcox, K. S..

14 recordsLinked to original sources

bioRxiv2025

ASSESSMENT OF CELL-TYPE-SPECIFIC EXCITATORY SYNAPTIC STRENGTH IN THE DORSOLATERAL STRIATUM OF GOAL-DIRECTED AND HABITUAL COCAINE-SEEKING BEHAVIOR

With repeated exposure to addictive drugs, there is a shift from drug abuse to drug addiction that is mediated by the transition from goal-directed to habitual control. It is well known that the development of habitual control over behavior relies upon cell-type-specific synaptic changes in both D1 and D2 medium spiny neurons (MSNs) in dorsal striatum. Specifically, habitual behavior is mediated by increased synaptic strength in D2 MSNs in dorsolateral striatum (DLS), suggesting similar cell-type-specific synaptic changes may underlie the development of habitual cocaine-seeking behavior. However, cell-type-specific synaptic changes have not been evaluated in DLS in this context. Therefore, we trained rats to self-administer cocaine in a cocaine self-administration paradigm that allows for differentiation of goal-directed vs. habitual cocaine-seeking behavior. Moreover, we used a viral vector under a D2-specific promoter to fluorescently label D2 MSNs with eYFP in DLS. Evoked excitatory postsynaptic currents (EPSCs) were used to determine AMPA:NMDA receptor ratio and the rectification index. Surprisingly, we did not observe any significant differences in these measures in DLS of cocaine-seeking rats, regardless of whether cocaine seeking was under habitual control. Interestingly, preliminary observations revealed significant changes in the paired pulse ratio (PPR), suggesting that presynaptic mechanisms may be involved in the development of habitual control over cocaine seeking. Overall, however, these results suggest there are no changes in postsynaptic strength of D2 MSNs in the DLS of rats with an extended history of cocaine self-administration and regardless of whether the cocaine seeking is under goal-directed or habitual control. Significance StatementThe study of drug abuse and drug addiction represents a critical area of research with significant public health implications. Importantly, the underlying neurobiology of the transition between drug abuse and drug addiction is not well understood and insights to this transition may aid in the development of novel treatment options. Behaviorally, the shift from goal-directed to habitual control is thought to underly this transition. Much is known about the neurobiology of goal-directed and habitual behavior, however the transition in the context of drug-seeking is not well defined. We observed no significant differences in measures of synaptic strength, suggesting such postsynaptic neuroplasticity in the dorsolateral striatum is not involved in this transition.

neuroscience↗

bioRxiv2025

Investigating the role of cortical microglia in a mouse model of viral infection-induced seizures

Microglia, resident immune sentinels in the brain, are crucial in responding to tissue damage, infection, damage signals like purines (ATP/ ADP), and clearing cellular debris. It is currently unknown how microglial reactivity progresses and contributes to seizure development following Theilers Murine Encephalomyelitis Virus (TMEV) infection. Previously, our group has demonstrated that purinergic signaling in microglia is disrupted in the hippocampus of TMEV-infected mice. However, whether reactive cortical microglia also exhibit changes in purinergic signaling, cytokine levels, and purinergic receptors are unknown. Thus, we seek to evaluate region-based differences in microglial reactivity in the TMEV model. We employed a custom triple transgenic mouse line expressing tdTomato and GCaMP6f under a CX3CR1 Cre promoter and exogenously applied ATP/ADP to acute brain slice preparations from TMEV-infected mice and controls. Interestingly and in contrast to what is observed in hippocampus, we found that despite microglial reactivity in the cortex, microglia can respond to purinergic damage signals and engage calcium signaling pathways, comparable to PBS controls. Using a cytokine panel, we also found that pro-inflammatory cytokine levels (TNF-, IL-1 and IFN-{gamma}) are brain-region dependent in mice infected with TMEV. Using RNAScope-FISH, we observed increases in expression of purinergic receptors responsible for microglial motility (P2Y12R) and inflammation (P2X7R) in the cortex. Collectively our results suggest that following TMEV infection, microglial response to novel damage signals, as well as the production of proinflammatory cytokines, varies as a function of brain region.

neuroscience↗

bioRxiv2025

Seizure Circuit Activity in the Theilers Murine Encephalomyelitis Virus Model of Infection-induced Epilepsy Using Transient Recombination in Active Populations.

Epilepsy affects one in twenty-six individuals. A major cause of epilepsy worldwide is viral encephalitis. Central nervous system infections can provoke seizures in the short term and increase the risk of spontaneous, recurrent seizures post-infection. However, the neural mechanisms underlying seizures during acute infection are unknown. These neuronal changes can be studied in C57BL6/J mice infected with Theilers murine encephalomyelitis virus (TMEV). TMEV-infected mice experience seizures 3-8 days post-injection (DPI), clear the virus by DPI 14, and may develop chronic, acquired temporal lobe epilepsy. TMEV may incite seizures during the acute infection period through inflammation, reactive gliosis, and cell death in hippocampal area CA1. Here, we explore the neuronal circuits underlying acute seizures in TMEV-injected mice using c-Fos driven TRAP (targeted recombination in active populations). TRAP mice (c-Fos- CreERT2 x CAG-tdTomato) were injected with PBS or TMEV and gently handled on DPI 5 to induce seizures. 4-OHT was administered to mice either 1.5 or 3 hr after seizures to tag the active cells expressing c-Fos with tdTomato. After 1 week, the mice were sacrificed and whole mouse brains were sectioned and immunostained for tdTomato expression. Percent area of fluorescence was quantified, and comparisons were made between TMEV-injected mice and PBS controls, sites ipsilateral vs contralateral to TMEV injection site, and between sexes. TdTomato expression was elevated in the TMEV-injected mice in the ipsilateral and contralateral hippocampus, thalamus, lateral septal nucleus, basal ganglia, triangular septal nucleus, fornix, and corpus callosum. Critically, the expression pattern suggests that seizures induced on DPI 5 arise from the hilus, dentate gyrus, and CA3 hippocampal subregions. Generalized seizures during acute TMEV infection may have propagated to the contralateral hemisphere via CA3 and the hippocampal commissure. TRAP has not been previously utilized in the TMEV mouse model and these experiments address crucial questions regarding seizure spread during TMEV infection. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/655185v1_ufig1.gif" ALT="Figure 1000"> View larger version (20K): org.highwire.dtl.DTLVardef@bbcd75org.highwire.dtl.DTLVardef@1add030org.highwire.dtl.DTLVardef@3f3aa5org.highwire.dtl.DTLVardef@1233312_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

DynamoSort: Using machine learning approaches for the automatic classification of seizure dynamotypes

ObjectiveEpilepsy is characterised by unprovoked and recurring seizures, which can be electrically measured using electroencephalograms (EEG). To better understand the underlying mechanisms of seizures, researchers are exploring their temporal dynamics through the lens of dynamical systems modelling. Seizure initiation and termination patterns of spiking amplitude and frequency can be sorted into "dynamotypes", which may be able to serve as biomarkers for intervention. However, manual classification of these dynamotypes requires trained raters and is prone to variability. To address this, we developed DynamoSort, a machine-learning algorithm for automatic seizure onset and offset classification. MethodsWe used approximately 2100 seizures from an intra-amygdala kainic acid (IAK) mouse model of mesial temporal lobe epilepsy, categorized by five trained raters. MATLABs classification learner application was used to create an ensemble model to score and label dynamotypes of individual seizures based on spiking and frequency features. ResultsDynamotype classification of real EEG data lacks a definitive ground truth, with mean inter-rater agreement at 73.4% for onset and 64.2% for offset types. Despite this, DynamoSort achieved a mean area under the curve (AUC) of 0.81 for onset and a mean AUC of 0.75 for offset types. Machine-human agreement was not significantly different from human-to-human agreement. To address the lack of ground truth in ratings, DynamoSort assigns probabilistic scores (-20 to 20), to indicate similarity to each seizure dynamotype based on spiking features, allowing for a characterization of seizure dynamics on a spectrum rather than the traditional qualitative taxonomy. SignificanceAutomating the classification of dynamotypes is a critical step for their inclusion as a biomarker in clinical and research applications. DynamoSort is a straightforward, open-access tool that uses automatic labelling and probabilistic scoring to quantify subtle changes in seizure onset and offset dynamics. Key PointsO_LIDynamotypes are a promising seizure categorization system, but is prone to interrater variability and lacks a ground truth. C_LIO_LIMachine learning can be used to automatically classify seizure onsets and offsets into appropriate dynamotypes based on spike features. C_LIO_LIAgreement between DynamoSort and human raters rivals typical agreement rates in trained human raters. C_LIO_LIDynamoSort uses probabilistic scoring to quantify subtle changes in seizure onset and offset, allowing for a quantitative characterisation. C_LI

neuroscience↗

bioRxiv2024

Development of a preclinical screening platform for clinically relevant therapy of Dravet syndrome

BackgroundPatients with drug-resistant epilepsy, including Dravet syndrome (DS), are frequently prescribed multiple antiseizure medications (ASMs). Nevertheless, people with DS often have inadequate seizure control, and there is an ongoing unmet clinical need to identify novel therapeutics. As a proof-of-principle study to further validate and characterize the Scn1aA1783V/WT mouse model and identify a drug screening paradigm with face, construct, and predictive value, we assessed the efficacy of subchronic administration of stiripentol add-on to clobazam and valproic acid at clinically relevant doses using the Scn1aA1783V/WT mouse model. MethodsWe evaluated the efficacy of STP add-on to CLB and VPA using hyperthermia-induced and video-EEG monitoring of spontaneous seizure tests following a 14-day treatment. VPA was delivered via osmotic minipump, while STP and CLB were administered via food pellets delivered through automatic feeders. Bioanalytical assays were performed to evaluate drug concentrations in plasma and brain using liquid chromatography-tandem mass spectrometry. ResultsSTP, CLB, N-desmethylclobazam, and VPA all yielded plasma concentrations within the human therapeutic plasma concentrations range. STP added to CLB and VPA significantly elevated the seizing temperatures in the hyperthermia-induced seizure assay. CLB, VPA, and STP coadministration significantly reduced spontaneous seizure frequency compared to CLB and VPA combined. SignificanceThis research lays the groundwork for exploring effective add-on compounds to CLB and VPA in treating DS. The study further highlights the utility of the Scn1aA1783V/WT mice in discovering therapies for DS-associated pharmacoresistant seizures. Key pointsO_LIIntegrating pharmacokinetic studies to guide the selection of doses in preclinical studies to achieve target concentrations comparable to the human therapeutic range is crucial in successfully translating animal drug development studies to clinical use. C_LIO_LISTP add-on to CLB and VPA significantly reduced spontaneous seizure frequency in Scn1aA1783V/WT mice. C_LIO_LIA triple-drug polytherapy approach that mimics the clinical treatment paradigm will be an essential preclinical drug screening strategy for identifying novel investigational compounds for Dravet syndrome. C_LI

pharmacology and toxicology↗

bioRxiv2024

A method for focused ultrasound (FUS) neuromodulation with simultaneous electroencephalogram recordings in awake, head-fixed mice with temporal lobe epilepsy

Transcranial focused ultrasound (FUS) may be a promising neuromodulation technology for treating people with epilepsy whose seizures are drug resistant. Prior studies have shown seizure suppression in animal studies using FUS. However, most of these studies were performed in evoked seizure models and not in animal models of epilepsy. Evoked seizure models do not exhibit the pathophysiology of epilepsy and do not exhibit spontaneous recurrent seizures, which define epilepsy. For translation to humans, there is a critical need to determine the specific FUS stimulation parameters that reduce spontaneous recurrent seizures in a chronic disease model of epilepsy. To achieve this goal, we developed and optimized an approach to determine the effects of ultrasonic stimulation on metrics of seizure-like events (SLEs) in awake, head-fixed mice within the intrahippocampal kainate (IHK) mouse model of temporal lobe epilepsy (TLE). A proof-of-principle study demonstrated that two target (bilateral and contralateral to the kainic acid injection site) stimulation conditions and two FUS parameter sets (low and high pressure) could be combined with the ability to simultaneously record hippocampal electroencephalograms. We also provide a method for analysis of the effects of FUS stimulation on the metrics of SLEs (interevent duration, SLE duration, and spike frequency).

bioengineering↗

bioRxiv2024

Reactive microglia fail to respond to environmental damage signals in a viral-induced mouse model of temporal lobe epilepsy

Microglia are highly adaptable innate immune cells that rapidly respond to damage signals in the brain through adoption of a reactive phenotype and production of defensive inflammatory cytokines. Microglia express a distinct transcriptome, encoding receptors that allow them to dynamically respond to pathogens, damage signals, and cellular debris. Expression of one such receptor, the microglia-specific purinergic receptor P2ry12, is known to be downregulated in reactive microglia. Here, we explore the microglial response to purinergic damage signals in reactive microglia in the TMEV mouse model of viral brain infection and temporal lobe epilepsy. Using two-photon calcium imaging in acute hippocampal brain slices, we found that the ability of microglia to detect damage signals, engage calcium signaling pathways, and chemoattract towards laser-induced tissue damage was dramatically reduced during the peak period of seizures, cytokine production, and infection. Using combined RNAscope in situ hybridization and immunohistochemistry, we found that during this same stage of heightened infection and seizures, microglial P2ry12 expression was reduced, while the pro-inflammatory cytokine TNF-a expression was upregulated in microglia, suggesting that the depressed ability of microglia to respond to new damage signals via P2ry12 occurs during the time when local elevated cytokine production contributes to seizure generation following infection. Therefore, changes in microglial purinergic receptors during infection likely limit the ability of reactive microglia to respond to new threats in the CNS and locally contain the scale of the innate immune response in the brain.

neuroscience↗

bioRxiv2023

Development of an MR-guided focused ultrasound (MRgFUS) lesioning approach for small and deep structures in the rat brain

ObjectiveHigh-intensity magnetic resonance-guided focused ultrasound (MRgFUS) is a noninvasive therapy to lesion brain tissue, used clinically in patients and preclinically in several animal models. Challenges with focused ablation in rodent brains can include skull and near-field heating and accurately targeting small and deep brain structures. We overcame these challenges by creating a novel method consisting of a craniectomy skull preparation, a high-frequency transducer (3 MHz) with a small ultrasound focal spot, a transducer positioning system with an added manual adjustment of [~]0.1 mm targeting accuracy, and MR acoustic radiation force imaging for confirmation of focal spot placement. MethodsThe study consisted of two main parts. First, two skull preparation approaches were compared. A skull thinning approach (n=7 lesions) was compared to a craniectomy approach (n=22 lesions), which confirmed a craniectomy was necessary to decrease skull and near-field heating. Second, the two transducer positioning systems were compared with the fornix chosen as a subcortical ablation target. We evaluated the accuracy of targeting using a high-frequency transducer with a small ultrasound focal spot and MR acoustic radiation force imaging. ResultsComparing a motorized adjustment system ([~]1 mm precision, n=17 lesions) to the motorized system with an added micromanipulator ([~]0.1 mm precision, n=14 lesions), we saw an increase in the accuracy of targeting the fornix by 133%. The described work allows for repeatable and accurate targeting of small and deep structures in the rodent brain, such as the fornix, enabling the investigation of neurological disorders in chronic disease models.

bioengineering↗

bioRxiv2023

Utilizing an acute hyperthermia-induced seizure test and pharmacokinetic studies to establish optimal dosing regimens in a mouse model of Dravet syndrome

ObjectiveThe current standard of care for Dravet Syndrome includes polytherapy after inadequate seizure control with one or more monotherapy approaches. Treatment guidelines are often based on expert opinions, and finding an optimal balance between seizure control and adverse drug effects can be challenging. This study utilizes efficacy and pharmacokinetic analysis of a second-line treatment regimen that combines clobazam and sodium valproate with an add-on drug as a proof-of-principle approach to establish an effective therapeutic regimen in a preclinical mouse model of Dravet Syndrome. MethodWe evaluated the efficacy of add-on therapies stiripentol, cannabidiol, lorcaserin, or fenfluramine to clobazam and sodium valproate against hyperthermia-induced seizures in Scn1aA1783V/WT mice. Clobazam, N-desmethyl clobazam (an active metabolite of clobazam), sodium valproate, stiripentol, and cannabidiol concentrations were quantified in plasma and brain using liquid chromatography-tandem mass spectrometry for the combinations deemed effective against hyperthermia-induced seizures. The concentration data were used to calculate pharmacokinetic parameters via non-compartmental analysis in Phoenix WinNonLin. ResultsHigher doses of stiripentol or cannabidiol, in combination with clobazam and sodium valproate, were effective against hyperthermia-induced seizures in Scn1aA1783V/WT mice. In Scn1aWT/WT mice, brain clobazam and N-desmethyl clobazam concentrations were higher in the triple-drug combinations than in the clobazam monotherapy. Stiripentol and cannabidiol brain concentrations were greater in the triple-drug therapy than when given alone. InterpretationA polypharmacy strategy may be a practical preclinical approach to identifying efficacious compounds for Dravet Syndrome. The drug-drug interactions between compounds used in this study may explain the potentiated efficacy of some combination therapies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/560653v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@70d9a7org.highwire.dtl.DTLVardef@e18a26org.highwire.dtl.DTLVardef@134c74aorg.highwire.dtl.DTLVardef@8065d_HPS_FORMAT_FIGEXP M_FIG C_FIG Key findingsThe hyperthermia-induced seizure assay in Scn1aA1783V/WT mice can identify efficacious antiseizure medications. A triple-drug administration paradigm was designed that mimics clinical standards for add-on therapies in DS. Stiripentol and cannabidiol were effective against hyperthermia-induced seizures when co-administered with clobazam and sodium valproate. Potential drug-drug interactions between compounds may explain the potentiated antiseizure effect in triple-drug therapies. The triple-drug "add-on" therapy approach may be a valuable preclinical strategy for screening investigational compounds for DS, an assay offered at the ETSP.

pharmacology and toxicology↗

bioRxiv2022

Evaluating the efficacy of prototype antiseizure drugs using a preclinical pharmacokinetic approach

ObjectivePharmacokinetics (PK) of a drug drive its exposure, efficacy, and tolerability. A thorough preclinical PK assessment of antiseizure medications (ASMs) is therefore essential to evaluate the clinical potential. We tested protection against evoked seizures of prototype ASMs in conjunction with analysis of plasma and brain PK as a proof-of-principle study to enhance our understanding of drug efficacy and duration of action using rodent seizure models. MethodsIn vivo seizure protection assays were performed in adult male CF-1 mice and Sprague-Dawley rats. Clobazam (CLB), N-desmethylclobzam (NCLB), carbamazepine (CBZ), carbamazepine-10,11-epoxide (CBZE), valproic acid (VPA), and levetiracetam (LEV) concentrations were quantified in plasma and brain using liquid chromatography-tandem mass spectrometry. Mean concentrations of each analyte were calculated and used to determine PK parameters via non-compartmental analysis in Phoenix WinNonLin. ResultsNCLB concentrations were approximately 10-fold greater than CLB in mice. The antiseizure profile of CLB was partially sustained by NCLB in mice. CLB concentrations were lower in rats than in mice. CBZE plasma exposures were approximately 70% of CBZ in both mice and rats, likely contributing to the antiseizure effect of CBZ. VPA showed a relatively short half-life in both mice and rats, which correlated with a sharp decline in efficacy. LEV had a prolonged brain and plasma half-life, associated with a prolonged duration of action in mice. SignificanceThe study demonstrates the utility of PK analyses for understanding the seizure protection time-course in mice and rats. The data indicate that distinct PK profiles of ASMs between mice and rats likely drive differences in drug efficacy between rodent models. Key PointsO_LIThere exist potential contributions of active metabolites to the efficacy of some ASMs. C_LIO_LIThe utility of preclinical PK assessment of ASM is critical to guide our insight into a drug efficacy profile and provide a framework for subchronic dosing strategies. C_LIO_LISpecies-specific variations in PK profiles of ASMs in rodent models of epilepsy may underpin the differences in antiseizure effect in these models. C_LIO_LIPre-clinical drug screening of ASMs should include a (sub)chronic dosing paradigm to better mimic the dosing regimen in the clinic. C_LI

neuroscience↗

bioRxiv2021

Evaluation of spontaneous seizure activity, sex-dependent differences, behavioral comorbidities, and alterations in CA1 neuron firing properties in a mouse model of Dravet Syndrome

Dravet syndrome (DS) is a rare childhood epilepsy disorder resulting in spontaneous, recurrent seizures (SRS) and behavioral co-morbidities. To facilitate the discovery and development of anti-seizure drugs for DS, the contract site of the NINDS Epilepsy Therapy Screening Program (ETSP) has continued to evaluate a mouse model of DS. Scn1aA1783V/WT mice exhibited increased hyperactivity, thigmotaxis, and deficits in nest-building behavior. Ex-vivo brain slice electrophysiology experiments revealed increased excitability of hippocampal CA1 neurons specifically due to increased action potential firing frequency in response to brief depolarizations and decreased frequency of spontaneous GABAergic synaptic events. A video-EEG study revealed mice had on average, 1 seizure per day, with males seizing significantly more frequently than females. Increased proportion of seizure activity occurred during the dark phase of the light/dark cycle in both sexes. While clobazam, a drug commonly prescribed to patients with DS, had no effect on SRS activity at the tested doses, the seizure history and frequency observed in this study aids in determining the sample sizes and experimental timeline needed for adequately powered preclinical drug studies. Overall, this study provides a broad description of the Scn1aA1783V/WT mouse and highlights the utility of this model in therapy discovery.

pharmacology and toxicology↗

bioRxiv2020

Development of an Antiepileptogenesis Drug Screening Platform: Effects of Everolimus and Phenobarbital

ObjectiveThe kainic acid (KA)-induced status epilepticus (SE) model in rats is an etiologically-relevant animal model of epileptogenesis. Just as in patients, who develop temporal lobe epilepsy (TLE) following SE, this rat model of KA-induced SE very closely recapitulates many of the clinical and pathological characteristics of human TLE that arise following SE or another neurological insult. Spontaneous recurrent seizures (SRS) in TLE can present after a latent period following a neurological insult (TBI, SE event, viral infection, etc.). Moreover, this rat model of TLE is ideally suited for preclinical studies to evaluate the long-term process of epileptogenesis and screen putative disease-modifying/antiepileptogenic agents. This report details the pharmacological characterization and methodological refinement of a moderate-throughput drug screening program using the post KA-induced SE model of epileptogenesis in male Sprague Dawley rats to identify potential agents that may prevent or modify the onset or severity of SRS. Specifically, we sought to demonstrate whether our protocol could prevent the development of SRS, or lead to a reduced frequency/severity of SRS. MethodsRats were administered everolimus (2-3 mg/kg, P.O. commencing at 1, 2, or 24-hrs after SE onset) or phenobarbital (60 mg/kg, beginning 1 hr after SE onset). The rats in all studies (n=12/treatment dose/study) were then followed intermittently by video-EEG monitoring; i.e., 2-weeks on/2-weeks off, 2-weeks on epochs to determine latency to onset of SRS, and disease burden following SRS onset. ResultsWhile there were no adverse side effects observed in any of our studies, no treatment conferred a significant disease modifying effect, nor did any agent prevent the presentation of SRS by 6 weeks post-SE onset. ConclusionsWhile neither phenobarbital nor everolimus administered at several time points post-SE onset prevented the development of SRS, we herein demonstrate a moderate-throughput screen for potential antiepileptogenic agents in an etiologically-relevant rodent model of TLE. Key PointsO_LIDisease-modifying therapies are needed to prevent or attenuate the burden of epilepsy in at-risk individuals. C_LIO_LIWe report a moderate-throughput screening protocol to identify disease-modifying agents in a rat post-kainic acid status epilepticus model. C_LIO_LIEverolimus was administered at multiple time points post-status epilepticus with no effect on spontaneous seizures up to 6 weeks later. C_LIO_LIRepeated administration of phenobarbital also did not prevent the development of spontaneous recurrent seizures up to 6 weeks post SE. C_LIO_LIWhile we did not identify any effect of either agent, our approach provides a moderate-throughput screen for antiepileptogenesis. C_LI

neuroscience↗

bioRxiv2020

Spontaneous recurrent seizures in an intra-amygdala kainate microinjection model of temporal lobe epilepsy are differentially sensitive to antiseizure drugs

The discovery and development of novel antiseizure drugs (ASDs) that are effective in controlling pharmacoresistant spontaneous recurrent seizures (SRSs) continues to represent a significant unmet clinical need. The Epilepsy Therapy Screening Program (ETSP) has undertaken efforts to address this need by adopting animal models that represent the salient features of human pharmacoresistant epilepsy and employing these models for preclinical testing of investigational ASDs. One such model that has garnered increased interest in recent years is the mouse variant of the Intra-Amygdala Kainate (IAK) microinjection model of mesial temporal lobe epilepsy (MTLE). In establishing a version of this model, several methodological variables were evaluated for their effect(s) on pertinent quantitative endpoints. Although administration of a benzodiazepine 40 minutes after kainate (KA) induced status epilepticus (SE) is commonly used to improve survival, data presented here demonstrates similar outcomes (mortality, hippocampal damage, latency periods, and 90-day SRS natural history) between mice given midazolam and those that were not. Using a version of this model that did not interrupt SE with a benzodiazepine, a 90-day natural history study was performed and survival, latency periods, SRS frequencies and durations, and SRS clustering data were quantified. Finally, an important step towards model adoption is to assess the sensitivities or resistances of SRSs to a panel of approved and clinically used ASDs. Accordingly, the following ASDs were evaluated for their effects on SRSs in these mice: phenytoin (20 mg/kg, b.i.d.), carbamazepine (30 mg/kg, t.i.d.), valproate (240 mg/kg, t.i.d.), diazepam (4 mg/kg, b.i.d.), and phenobarbital (25 and 50 mg/kg, b.i.d.). Valproate, diazepam, and phenobarbital significantly attenuated SRS frequency relative to vehicle controls at doses devoid of observable adverse behavioral effects. Only diazepam significantly increased seizure freedom. Neither phenytoin nor carbamazepine significantly altered SRS frequency or freedom under these experimental conditions. These data demonstrate that SRSs in this IAK model of MTLE are pharmacoresistant to two representative sodium channel-inhibiting ASDs (phenytoin and carbamazepine) but not to GABA receptor modulating ASDs (diazepam and phenobarbital) or a mixed-mechanism ASD (valproate). Accordingly, this model is being incorporated into the NINDS-funded ETSP testing platform for treatment resistant epilepsy. HighlightsO_LIAn intra-amygdala kainate model of TLE was evaluated for pharmacoresistant seizures C_LIO_LIAdministration of midazolam during status epilepticus did not affect mortality C_LIO_LIModel characteristics were evaluated over a 90-day natural history study C_LIO_LISpontaneous seizures were resistant to phenytoin and carbamazepine C_LIO_LISpontaneous seizures were sensitive to valproic acid, diazepam, and phenobarbital C_LI

neuroscience↗

bioRxiv2020

Development of an Antiseizure Drug Screening Platform for Dravet Syndrome at the NINDS contract site for the Epilepsy Therapy Screening Program

ObjectiveDravet syndrome (DS) is a rare, but catastrophic genetic epilepsy, with 80% of patients with carrying a mutation in the SCN1A gene. Currently, no anti-seizure drug (ASD) exists that adequately controls seizures. Patients with DS often present clinically with a febrile seizure and generalized tonic-clonic seizures that continue throughout life. To facilitate the development of ASDs for DS, the contract site of the NINDS Epilepsy Therapy Screening Program (ETSP) has evaluated a mouse model of DS using the conditional knock-in Scn1aA1783V/WT mouse. MethodsSurvival rates and temperature thresholds for Scn1aA1783V/WT were determined. Prototype ASDs were administered via intraperitoneal injections at the time-to-peak effect, which was previously determined, prior to the induction of hyperthermia-induced seizures. Protection was determined if ASDs significantly increased the temperature at which Scn1aA1783V/WT mice seized. ResultsApproximately 50% of Scn1aA1783V/WT survive to adulthood and all have hyperthermia-induce seizures. The results suggest that hyperthermia-induced seizures in this model of DS are highly refractory to a battery of ASDs. Exceptions were clobazam, tiagabine, and the combination of clobazam and valproic acid with add-on stiripentol, which elevated seizure thresholds SignificanceOverall, the data demonstrate the proposed model for DS is suitable for screening novel compounds for the ability to block hyperthermia-induced seizures and heterozygous mice can be evaluated repeatedly over the course of several weeks, allowing for higher throughput screening. Key Points O_LIScn1aA1783V/WT mice have a 50% survival rate and all have hyperthermia-induced seizures. C_LIO_LICommon DS treatments such as CLB and combinatorial therapy of CLB, VPA, and STP increase temperature thresholds in Scn1aA1783V/WT mice. C_LIO_LISodium channel blockers, such as CBZ and LTG, decrease temperature thresholds of Scn1aA1783V/WT mice as predicted. C_LIO_LIScn1aA1783V/WT mice are highly pharmacoresitant to common ASDs C_LIO_LIThe Scn1aA1783V/WT may be a useful preclinical drug screening platform for the treatment of DS. C_LI

pharmacology and toxicology↗