Enhanced cGAS-STING-dependent interferon signaling associated with mutations in ATAD3A.

Mitochondrial DNA (mtDNA) has been suggested to drive immune system activation, but the induction of interferon signaling by mtDNA has not been demonstrated in a Mendelian mitochondrial disease. We initially ascertained two patients, one with a purely neurological phenotype and one with features suggestive of systemic sclerosis in a syndromic context, and found them both to demonstrate enhanced interferon-stimulated gene (ISG) expression in blood. We determined each to harbor a previously described de novo dominant-negative heterozygous mutation in ATAD3A, encoding ATPase family AAA domain-containing protein 3A (ATAD3A). We identified five further patients with mutations in ATAD3A and recorded up-regulated ISG expression and interferon α protein in four of them. Knockdown of ATAD3A in THP-1 cells resulted in increased interferon signaling, mediated by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). Enhanced interferon signaling was abrogated in THP-1 cells and patient fibroblasts depleted of mtDNA. Thus, mutations in the mitochondrial membrane protein ATAD3A define a novel type I interferonopathy.

Perampanel, a potent AMPA receptor antagonist, protects against tetramethylenedisulfotetramine-induced seizures and lethality in mice: comparison with diazepam.

Tetramethylenedisulfotetramine (TETS), a noncompetitive GABAA receptor antagonist, is a potent, highly lethal convulsant that is considered to be a chemical threat agent. Here, we assessed the ability of the AMPA receptor antagonist perampanel to protect against TETS-induced seizures and lethality in mice when administered before or after treatment with the toxicant. For comparison, we conducted parallel testing with diazepam, which is a first-line treatment for chemically induced seizures in humans. Pre-treatment of mice with either perampanel (1-4 mg/kg, i.p.) or diazepam (1-5 mg/kg, i.p.) conferred protection in a dose-dependent fashion against tonic seizures and lethality following a dose of TETS (0.2 mg/kg, i.p.) that rapidly induces seizures and death. The ED50 values for protection against mortality were 1.6 mg/kg for perampanel and 2.1 mg/kg for diazepam. Clonic seizures were unaffected by perampanel and only prevented in a minority of animals by high-dose diazepam. Neither treatment prevented myoclonic body twitches. Perampanel and diazepam also conferred protection against tonic seizures and lethality when administered 15 min following a 0.14 mg/kg, i.p., dose of TETS and 5 min following a 0.2 mg/kg, i.p., dose of TETS. Both posttreatments were highly potent at reducing tonic seizures and lethality in animals exposed to the lower dose of TETS whereas greater doses of both treatments were required in animals exposed to the larger dose of TETS. Neither treatment was as effective suppressing clonic seizures. In an experiment where 0.4 mg/kg TETS was administered by oral gavage and the treatment drugs were administered 5 min later, perampanel only partially protected against lethality whereas diazepam produced nearly complete protection. We conclude that perampanel and diazepam protect against TETS-induced tonic seizures and lethality but have less impact on clonic seizures. Both drugs could have utility in the treatment of TETS intoxication but neither eliminates all seizure activity.

cGAS-mediated induction of type I interferon due to inborn errors of histone pre-mRNA processing.

Inappropriate stimulation or defective negative regulation of the type I interferon response can lead to autoinflammation. In genetically uncharacterized cases of the type I interferonopathy Aicardi-Goutières syndrome, we identified biallelic mutations in LSM11 and RNU7-1, which encode components of the replication-dependent histone pre-mRNA-processing complex. Mutations were associated with the misprocessing of canonical histone transcripts and a disturbance of linker histone stoichiometry. Additionally, we observed an altered distribution of nuclear cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) and enhanced interferon signaling mediated by the cGAS-stimulator of interferon genes (STING) pathway in patient-derived fibroblasts. Finally, we established that chromatin without linker histone stimulates cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) production in vitro more efficiently. We conclude that nuclear histones, as key constituents of chromatin, are essential in suppressing the immunogenicity of self-DNA.

Allopregnanolone and perampanel as adjuncts to midazolam for treating diisopropylfluorophosphate-induced status epilepticus in rats.

Combinations of midazolam, allopregnanolone, and perampanel were assessed for antiseizure activity in a rat diisopropylfluorophosphate (DFP) status epilepticus model. Animals receiving DFP followed by atropine and pralidoxime exhibited continuous high-amplitude rhythmical electroencephalography (EEG) spike activity and behavioral seizures for more than 5 hours. Treatments were administered intramuscularly 40 min after DFP. Seizures persisted following midazolam (1.8 mg/kg). The combination of midazolam with either allopregnanolone (6 mg/kg) or perampanel (2 mg/kg) terminated EEG and behavioral status epilepticus, but the onset of the perampanel effect was slow. The combination of midazolam, allopregnanolone, and perampanel caused rapid and complete suppression of EEG and behavioral seizures. In the absence of DFP, animals treated with the three-drug combination were sedated but not anesthetized. Animals that received midazolam alone exhibited spontaneous recurrent EEG seizures, whereas those that received the three-drug combination did not, demonstrating antiepileptogenic activity. All combination treatments reduced neurodegeneration as assessed with Fluoro-Jade C staining to a greater extent than midazolam alone, and most reduced astrogliosis as assessed by GFAP immunoreactivity but had mixed effects on markers of microglial activation. We conclude that allopregnanolone, a positive modulator of the GABAA receptor, and perampanel, an AMPA receptor antagonist, are potential adjuncts to midazolam in the treatment of benzodiazepine-refractory organophosphate nerve agent-induced status epilepticus.

The chemical convulsant diisopropylfluorophosphate (DFP) causes persistent neuropathology in adult male rats independent of seizure activity.

Organophosphate (OP) threat agents can trigger seizures that progress to status epilepticus, resulting in persistent neuropathology and cognitive deficits in humans and preclinical models. However, it remains unclear whether patients who do not show overt seizure behavior develop neurological consequences. Therefore, this study compared two subpopulations of rats with a low versus high seizure response to diisopropylfluorophosphate (DFP) to evaluate whether acute OP intoxication causes persistent neuropathology in non-seizing individuals. Adult male Sprague Dawley rats administered DFP (4 mg/kg, sc), atropine sulfate (2 mg/kg, im), and pralidoxime (25 mg/kg, im) were monitored for seizure activity for 4 h post-exposure. Animals were separated into groups with low versus high seizure response based on behavioral criteria and electroencephalogram (EEG) recordings. Cholinesterase activity was evaluated by Ellman assay, and neuropathology was evaluated at 1, 2, 4, and 60 days post-exposure by Fluoro-Jade C (FJC) staining and micro-CT imaging. DFP significantly inhibited cholinesterase activity in the cortex, hippocampus, and amygdala to the same extent in low and high responders. FJC staining revealed significant neurodegeneration in DFP low responders albeit this response was delayed, less persistent, and decreased in magnitude compared to DFP high responders. Micro-CT scans at 60 days revealed extensive mineralization that was not significantly different between low versus high DFP responders. These findings highlight the importance of considering non-seizing patients for medical care in the event of acute OP intoxication. They also suggest that OP intoxication may induce neurological damage via seizure-independent mechanisms, which if identified, might provide insight into novel therapeutic targets.

Natural polyphenols in preclinical models of epilepsy.

Natural polyphenols are being tested both in preclinical and clinical settings for the treatment of different neurological disorders. The article describes the outcome of three polyphenols, resveratrol, epigallocatechin gallate, and quercetin, in preclinical animal models of epilepsy (both acute and chronic) and epileptogenesis. In theory, the antioxidant and neuroprotective properties of these natural polyphenols might be valuable in the management of acute seizures and the prevention of epileptogenesis. It is fascinating to observe that these polyphenols have a capacity to alter various signaling processes involved in the pathogenesis of epilepsy. The antiepileptic or antiseizure potential with these molecules delivers a mixed outcome. Some studies have demonstrated the usefulness of these molecules in preclinical models of epilepsy; however, contrary to the findings also exist. These molecules have poor bioavailability that may remain as the limiting factor in their clinical effects. The use of nanotechnology and other techniques have been tested to enhance bioavailability and brain penetration. There are no randomized double-blinded clinical studies establishing their antiepileptic effects in humans. It is concluded that more preclinical mechanism-based studies are needed to deliver a more certain picture regarding the use of natural polyphenols in the treatment of epilepsy.

Persistent behavior deficits, neuroinflammation, and oxidative stress in a rat model of acute organophosphate intoxication.

Current medical countermeasures for organophosphate (OP)-induced status epilepticus (SE) are not effective in preventing long-term morbidity and there is an urgent need for improved therapies. Rat models of acute intoxication with the OP, diisopropylfluorophosphate (DFP), are increasingly being used to evaluate therapeutic candidates for efficacy in mitigating the long-term neurologic effects associated with OP-induced SE. Many of these therapeutic candidates target neuroinflammation and oxidative stress because of their implication in the pathogenesis of persistent neurologic deficits associated with OP-induced SE. Critical to these efforts is the rigorous characterization of the rat DFP model with respect to outcomes associated with acute OP intoxication in humans, which include long-term electroencephalographic, neurobehavioral, and neuropathologic effects, and their temporal relationship to neuroinflammation and oxidative stress. To address these needs, we examined a range of outcomes at later times post-exposure than have previously been reported for this model. Adult male Sprague-Dawley rats were given pyridostigmine bromide (0.1 mg/kg, im) 30 min prior to administration of DFP (4 mg/kg, sc), which was immediately followed by atropine sulfate (2 mg/kg, im) and pralidoxime (25 mg/kg, im). This exposure paradigm triggered robust electroencephalographic and behavioral seizures that rapidly progressed to SE lasting several hours in 90% of exposed animals. Animals that survived DFP-induced SE (~70%) exhibited spontaneous recurrent seizures and hyperreactive responses to tactile stimuli over the first 2 months post-exposure. Performance in the elevated plus maze, open field, and Pavlovian fear conditioning tests indicated that acute DFP intoxication reduced anxiety-like behavior and impaired learning and memory at 1 and 2 months post-exposure in the absence of effects on general locomotor behavior. Immunohistochemical analyses revealed significantly increased expression of biomarkers of reactive astrogliosis, microglial activation and oxidative stress in multiple brain regions at 1 and 2 months post-DFP, although there was significant spatiotemporal heterogeneity across these endpoints. Collectively, these data largely support the relevance of the rat model of acute DFP intoxication as a model for acute OP intoxication in the human, and support the hypothesis that neuroinflammation and/or oxidative stress represent potential therapeutic targets for mitigating the long-term neurologic sequelae of acute OP intoxication.

Defects of mitochondrial RNA turnover lead to the accumulation of double-stranded RNA in vivo.

The RNA helicase SUV3 and the polynucleotide phosphorylase PNPase are involved in the degradation of mitochondrial mRNAs but their roles in vivo are not fully understood. Additionally, upstream processes, such as transcript maturation, have been linked to some of these factors, suggesting either dual roles or tightly interconnected mechanisms of mitochondrial RNA metabolism. To get a better understanding of the turn-over of mitochondrial RNAs in vivo, we manipulated the mitochondrial mRNA degrading complex in Drosophila melanogaster models and studied the molecular consequences. Additionally, we investigated if and how these factors interact with the mitochondrial poly(A) polymerase, MTPAP, as well as with the mitochondrial mRNA stabilising factor, LRPPRC. Our results demonstrate a tight interdependency of mitochondrial mRNA stability, polyadenylation and the removal of antisense RNA. Furthermore, disruption of degradation, as well as polyadenylation, leads to the accumulation of double-stranded RNAs, and their escape out into the cytoplasm is associated with an altered immune-response in flies. Together our results suggest a highly organised and inter-dependable regulation of mitochondrial RNA metabolism with far reaching consequences on cellular physiology.

An update of cyclooxygenase (COX)-inhibitors in epilepsy disorders.

INTRODUCTION: Neuroinflammation has a critical role in brain disorders. Cyclooxygenase (COX) is one of the principal drug targets for the reduction of neuroinflammation; however, studies have yielded mixed results for COX-inhibitors in the treatment of diverse acute and chronic models of epilepsy. AREAS COVERED: The article covers the effects of COX-inhibitors in epilepsy disorders. A considerable emphasis has been placed on the antiepileptic and 'disease-modifying' properties of COX-1 and COX-2 inhibitors in various preclinical epilepsy models. EXPERT OPINION: The effect of COX-inhibitors on epilepsy is inconclusive. Studies have indicated beneficial effects in preclinical models; however, proconvulsant or no effects have also been observed. These molecules may have a bidirectional role with early neuroprotective and delayed neurotoxic effects. Further systematic preclinical studies to establish the use of COX-inhibitors in epilepsy are necessary.

Deregulated Expression of Mammalian lncRNA through Loss of SPT6 Induces R-Loop Formation, Replication Stress, and Cellular Senescence.

Extensive tracts of the mammalian genome that lack protein-coding function are still transcribed into long noncoding RNA. While these lncRNAs are generally short lived, length restricted, and non-polyadenylated, how their expression is distinguished from protein-coding genes remains enigmatic. Surprisingly, depletion of the ubiquitous Pol-II-associated transcription elongation factor SPT6 promotes a redistribution of H3K36me3 histone marks from active protein coding to lncRNA genes, which correlates with increased lncRNA transcription. SPT6 knockdown also impairs the recruitment of the Integrator complex to chromatin, which results in a transcriptional termination defect for lncRNA genes. This leads to the formation of extended, polyadenylated lncRNAs that are both chromatin restricted and form increased levels of RNA:DNA hybrid (R-loops) that are associated with DNA damage. Additionally, these deregulated lncRNAs overlap with DNA replication origins leading to localized DNA replication stress and a cellular senescence phenotype. Overall, our results underline the importance of restricting lncRNA expression.

Mitochondrial double-stranded RNA triggers antiviral signalling in humans.

Mitochondria are descendants of endosymbiotic bacteria and retain essential prokaryotic features such as a compact circular genome. Consequently, in mammals, mitochondrial DNA is subjected to bidirectional transcription that generates overlapping transcripts, which are capable of forming long double-stranded RNA structures1,2. However, to our knowledge, mitochondrial double-stranded RNA has not been previously characterized in vivo. Here we describe the presence of a highly unstable native mitochondrial double-stranded RNA species at single-cell level and identify key roles for the degradosome components mitochondrial RNA helicase SUV3 and polynucleotide phosphorylase PNPase in restricting the levels of mitochondrial double-stranded RNA. Loss of either enzyme results in massive accumulation of mitochondrial double-stranded RNA that escapes into the cytoplasm in a PNPase-dependent manner. This process engages an MDA5-driven antiviral signalling pathway that triggers a type I interferon response. Consistent with these data, patients carrying hypomorphic mutations in the gene PNPT1, which encodes PNPase, display mitochondrial double-stranded RNA accumulation coupled with upregulation of interferon-stimulated genes and other markers of immune activation. The localization of PNPase to the mitochondrial inter-membrane space and matrix suggests that it has a dual role in preventing the formation and release of mitochondrial double-stranded RNA into the cytoplasm. This in turn prevents the activation of potent innate immune defence mechanisms that have evolved to protect vertebrates against microbial and viral attack.

Curcumin in epilepsy disorders.

Curcumin, a principal curcuminoid present in turmeric, has an antioxidant, anti-inflammatory and neuroprotective properties. Preclinical studies have indicated its beneficial effect for the treatment of epilepsy disorders. The molecule has an anti-seizure potential in preclinical studies, including chemical and electrical models of acute and chronic epilepsy. Curcumin also possesses an anti-epileptogenic activity as it reduces spontaneous recurrent seizures severity in a kainate model of temporal lobe epilepsy. The antioxidant and anti-inflammatory nature of curcumin might be responsible for its observed anti-seizure effects; nevertheless, the exact mechanism is not yet clear. The poor availability of curcumin to the brain limits its use in clinics. The application of nanoliposome and liposome technologies has been tested to enhance its brain availability and penetrability. Unfortunately, there are no randomized, double-blinded controlled clinical trials validating the use of curcumin in epilepsy. The present article analyzes different preclinical evidence illustrating the effect of curcumin in seizure models. The review encourages carrying out clinical trials in this important area of research. In conclusion, curcumin might be beneficial in patients with epilepsy disorders, if its bioavailability issues are resolved.

RNA Helicase DDX1 Converts RNA G-Quadruplex Structures into R-Loops to Promote IgH Class Switch Recombination.

Class switch recombination (CSR) at the immunoglobulin heavy-chain (IgH) locus is associated with the formation of R-loop structures over switch (S) regions. While these often occur co-transcriptionally between nascent RNA and template DNA, we now show that they also form as part of a post-transcriptional mechanism targeting AID to IgH S-regions. This depends on the RNA helicase DDX1 that is also required for CSR in vivo. DDX1 binds to G-quadruplex (G4) structures present in intronic switch transcripts and converts them into S-region R-loops. This in turn targets the cytidine deaminase enzyme AID to S-regions so promoting CSR. Notably R-loop levels over S-regions are diminished by chemical stabilization of G4 RNA or by the expression of a DDX1 ATPase-deficient mutant that acts as a dominant-negative protein to reduce CSR efficiency. In effect, we provide evidence for how S-region transcripts interconvert between G4 and R-loop structures to promote CSR in the IgH locus.

Determination of minimal steady-state plasma level of diazepam causing seizure threshold elevation in rats.

OBJECTIVE: Diazepam, administered by the intravenous, oral, or rectal routes, is widely used for the management of acute seizures. Dosage forms for delivery of diazepam by other routes of administration, including intranasal, intramuscular, and transbuccal, are under investigation. In predicting what dosages are necessary to terminate seizures, the minimal exposure required to confer seizure protection must be known. Here we administered diazepam by continuous intravenous infusion to obtain near-steady-state levels, which allowed an assessment of the minimal levels that elevate seizure threshold. METHODS: The thresholds for various behavioral seizure signs (myoclonic jerk, clonus, and tonus) were determined with the timed intravenous pentylenetetrazol seizure threshold test in rats. Diazepam was administered to freely moving animals by continuous intravenous infusion via an indwelling jugular vein cannula. Blood samples for assay of plasma levels of diazepam and metabolites were recovered via an indwelling cannula in the contralateral jugular vein. RESULTS: The pharmacokinetic parameters of diazepam following a single 80-µg/kg intravenous bolus injection were determined using a noncompartmental pharmacokinetic approach. The derived parameters Vd , CL, t1/2α (distribution half-life) and t1/2ß (terminal half-life) for diazepam were, respectively, 608 mL, 22.1 mL/min, 13.7 minutes, and 76.8 minutes, respectively. Various doses of diazepam were continuously infused without or with an initial loading dose. At the end of the infusions, the thresholds for various behavioral seizure signs were determined. The minimal plasma diazepam concentration associated with threshold elevations was estimated at approximately 70 ng/mL. The active metabolites nordiazepam, oxazepam, and temazepam achieved levels that are expected to make only minor contributions to the threshold elevations. SIGNIFICANCE: Diazepam elevates seizure threshold at steady-state plasma concentrations lower than previously recognized. The minimally effective plasma concentration provides a reference that may be considered when estimating the diazepam exposure required for acute seizure treatment.

Distinctive Patterns of Transcription and RNA Processing for Human lincRNAs.

Numerous long intervening noncoding RNAs (lincRNAs) are generated from the mammalian genome by RNA polymerase II (Pol II) transcription. Although multiple functions have been ascribed to lincRNAs, their synthesis and turnover remain poorly characterized. Here, we define systematic differences in transcription and RNA processing between protein-coding and lincRNA genes in human HeLa cells. This is based on a range of nascent transcriptomic approaches applied to different nuclear fractions, including mammalian native elongating transcript sequencing (mNET-seq). Notably, mNET-seq patterns specific for different Pol II CTD phosphorylation states reveal weak co-transcriptional splicing and poly(A) signal-independent Pol II termination of lincRNAs as compared to pre-mRNAs. In addition, lincRNAs are mostly restricted to chromatin, since they are rapidly degraded by the RNA exosome. We also show that a lincRNA-specific co-transcriptional RNA cleavage mechanism acts to induce premature termination. In effect, functional lincRNAs must escape from this targeted nuclear surveillance process.

Investigational drugs for treating major depressive disorder.

INTRODUCTION: Treatment of patients suffering from major depression could be highly challenging for psychiatrists. Intractability as well as relapse is commonly seen among these patients, leading to functional impairment and poor quality of life. The present review discusses some of the novel investigational drugs that are under pre-clinical or clinical phases in the treatment of major depression. Areas covered: Molecules belonging to different classes such as triple reuptake inhibitors, opioid receptors, ionotropic and metabotropic glutamate receptors, and neurotrophin in the treatment of major depression are covered in this article. Expert opinion: Although the historical discovery of earlier antidepressant molecules (iproniazid and imipramine) is through serendipitous discovery, the present research focuses on discovering novel molecules based on our current pathophysiological knowledge of the disease condition. The fast-acting antidepressant property of N-methyl-d-aspartate (NMDA) receptor molecules, including ketamine is an exciting area of research. Other drug molecules such as amitifadine (triple reuptake inhibitor), ALKS-5461 (kappa receptor antagonist and mu opioidergic receptor agonist), rapastinel (NMDA glutamatergic receptor modulator) are under Phase-III clinical trials and could be approved in the near future for the treatment of major depression.

Propofol in the treatment of refractory migraine headaches.

INTRODUCTION: Refractory/intractable migraine headaches are associated with chronic pain that does not respond to standard care of treatment. Propofol(2,6-diisopropylphenol) in sub-anesthetic doses has been reported to be beneficial in such patients. The present article describes the complete drug profile of propofol in the management of these super-refractory migraine headaches. AREAS COVERED: The article covers different preclinical and clinical studies available in the literature. Expert commentary: Propofol is useful as an off-label drug molecule in an emergency situation of refractory migraines where it has been found to reduce the pain intensity. The molecule with a narrow therapeutic index and high abuse potential is prescribed only when conventional drugs fail to deliver any relief. There are not adequate double-blind crossover studies that substantiate the effectiveness of propofol in the treatment of migraine headaches. Furthermore, long-term outcomes for the use of propofol in migraine headaches requires an extensive investigation.

Pre- and post-exposure talampanel (GYKI 53773) against kainic acid seizures in neonatal rats.

BACKGROUND: AMPA receptors play an important role in the neurobiology of neonatal epilepsy. The present study evaluated the effect of talampanel, a potent and selective non-competitive antagonist of AMPA receptors, against kainic acid-induced continuous seizures (status epilepticus) and other behavioral abnormalities in neonatal rats. METHODS: Kainic acid was administered at doses of 2 or 4mg/kg, ip to induce seizures and status epilepticus in postnatal 7 days old rat neonates in pre- and post-exposure studies, respectively. RESULTS: Intraperitoneal administration of kainic acid (2 or 4mg/kg) resulted in forelimb/hind-limb scratching defined as automatism, continuous generalized tonic-clonic seizures with loss of righting reflex suggesting status epilepticus and tonic extension. Pre-exposure of talampanel (2.5-10mg/kg, ip) 30min before kainic acid did not affect the onset of kainic acid convulsions. Talampanel at 20mg/kg, ip delayed the commencement of tonic extension, but not status-induced by kainic acid. In contrast, talampanel (5 and 10mg/kg, ip) when administered 5min after kainic acid (4mg/kg, ip) postponed the onset of status epilepticus and tonic extension compared to vehicle treated group. Furthermore, talampanel (10mg/kg, ip) but not GYKI 52466 (20 or 50mg/kg, ip; a non-competitive AMPA/kainate receptor antagonist) stopped the ongoing status epilepticus when administered 10min after the administration of kainic acid. However, seizures re-occurred after 35.98±2.36min. CONCLUSION: The present results suggested that talampanel is protective in kainic acid-induced neonatal status epilepticus model; however, the time of administration is a crucial factor in determining its effectiveness.

On the anticonvulsant effect of allopregnanolone (a neurosteroid) in neonatal rats.

AIMS: Allopregnanolone has shown potent anticonvulsant activity in the adult brain. However, none of the studies have shown its effect in neonatal animal models of seizures. The current study explored the effect of allopregnanolone in animal models of neonatal status epilepticus. MAIN METHODS: Allopregnanolone was administered 10min before administration of kainic acid or 4-aminopyridine in postnatal 9 (PN9) day old rats. Various phases of convulsions such as latency to myoclonic jerks, continuous clonic movements with loss of righting reflex (status epilepticus) and mortality were measured; the effect was compared with its effect in pentylenetetrazol (PTZ) -induced generalized tonic-clonic convulsions. KEY FINDINGS: Exogenous administration of kainic acid (2mg/kg., i.p.) or 4-aminopyridine (5mg/kg., i.p.) in rat pups (PN9) resulted in continuous clonic movements with loss of righting reflex (status epilepticus). Pre-treatment with allopregnanolone at doses of 5 and 10mg/kg., i.p. dose-dependently delayed the onset of status epilepticus, but not myoclonic jerks. Allopregnanolone did not prevent kainic acid-induced mortality at theses doses. In the kainic acid model, pretreatment of bumetanide before allopregnanolone delayed various phases of convulsions; the effect was significantly higher compared to per se groups. Allopregnanolone only at the higher dose extended the latency of 4-aminopyridine-induced seizures. In contrast, allopregnanolone at a low dose markedly shielded neonatal rats against PTZ convulsions. SIGNIFICANCE: Allopregnanolone is protective in animal models of neonatal status epilepticus and generalized tonic-clonic convulsions and further clinical studies are required to establish its use in therapeutics.