Early onset epilepsy and sudden unexpected death in epilepsy with cardiac arrhythmia in mice carrying the early infantile epileptic encephalopathy 47 gain-of-function FHF1(FGF12) missense mutation.

OBJECTIVE: Fibroblast growth factor homologous factors (FHFs) are brain and cardiac sodium channel-binding proteins that modulate channel density and inactivation gating. A recurrent de novo gain-of-function missense mutation in the FHF1(FGF12) gene (p.Arg52His) is associated with early infantile epileptic encephalopathy 47 (EIEE47; Online Mendelian Inheritance in Man database 617166). To determine whether the FHF1 missense mutation is sufficient to cause EIEE and to establish an animal model for EIEE47, we sought to engineer this mutation into mice. METHODS: The Arg52His mutation was introduced into fertilized eggs by CRISPR (clustered regularly interspaced short palindromic repeats) editing to generate Fhf1R52H/F+ mice. Spontaneous epileptiform events in Fhf1R52H/+ mice were assessed by cortical electroencephalography (EEG) and video monitoring. Basal heart rhythm and seizure-induced arrhythmia were recorded by electrocardiography. Modulation of cardiac sodium channel inactivation by FHF1BR52H protein was assayed by voltage-clamp recordings of FHF-deficient mouse cardiomyocytes infected with adenoviruses expressing wild-type FHF1B or FHF1BR52H protein. RESULTS: All Fhf1R52H/+ mice experienced seizure or seizurelike episodes with lethal ending between 12 and 26 days of age. EEG recordings in 19-20-day-old mice confirmed sudden unexpected death in epilepsy (SUDEP) as severe tonic seizures immediately preceding loss of brain activity and death. Within 2-53 s after lethal seizure onset, heart rate abruptly declined from 572 ± 16 bpm to 108 ± 15 bpm, suggesting a parasympathetic surge accompanying seizures that may have contributed to SUDEP. Although ectopic overexpression of FHF1BR52H in cardiomyocytes induced a 15-mV depolarizing shift in voltage of steady-state sodium channel inactivation and slowed the rate of channel inactivation, heart rhythm was normal in Fhf1R52H/+ mice prior to seizure. SIGNIFICANCE: The Fhf1 missense mutation p.Arg52His induces epileptic encephalopathy with full penetrance in mice. Both Fhf1 (p.Arg52His) and Scn8a (p.Asn1768Asp) missense mutations enhance sodium channel Nav 1.6 currents and induce SUDEP with bradycardia in mice, suggesting an FHF1/Nav 1.6 functional axis underlying altered brain sodium channel gating in epileptic encephalopathy.

Tetramethylenedisulfotetramine neurotoxicity: What have we learned in the past 70 years?

Tetramethylenedisulfotetramine (tetramine, TETS, TMDT) is a seizure-producing neurotoxic chemical formed by the condensation of sulfamide and formaldehyde. Serendipitously discovered through an occupational exposure in 1949, it was promoted as a rodenticide but later banned worldwide due to its danger to human health. However, exceptional activity of the agent against rodent pests resulted in its clandestine manufacture with large numbers of inadvertent, intentional, and mass poisonings, which continue to this day. Facile synthesis, extreme potency, persistence, lack of odor, color, and taste identify it as an effective food adulterant and potential chemical agent of terror. No known antidote or targeted treatment is currently available. In this review we examine the origins of tetramethylenedisulfotetramine, from its identification as a neurotoxicant 70 years ago, through early research, to the most recent findings including the risk it poses in the post-911 world. Included is the information known regarding its in vitro pharmacology as a GABAA receptor channel antagonist, the toxic syndrome it produces in vivo, and its effect upon vulnerable populations. We also summarize the available information about potential therapeutic countermeasures and treatment strategies as well as the contribution of clinical development of TMDT poisoning to our understanding of epileptogenesis. Finally we identify gaps in our knowledge and suggest potentially fruitful directions for continued research on this dangerous, yet intriguing compound.

Developmental decrease in parvalbumin-positive neurons precedes increase in flurothyl-induced seizure susceptibility in the Brd2+/- mouse model of juvenile myoclonic epilepsy.

OBJECTIVE: BRD2 is a human gene repeatedly linked to and associated with juvenile myoclonic epilepsy (JME). Here, we define the developmental stage when increased seizure susceptibility first manifests in heterozygous Brd2+/- mice, an animal model of JME. We wanted to determine (1) whether seizure susceptibility correlates with the proven decrease of γ-aminobutyric acidergic (GABAergic) neuron numbers and (2) whether the seizure phenotype can be affected by sex hormones. METHODS: Heterozygous (Brd2+/-) and wild-type (wt) mice of both sexes were tested for flurothyl-induced seizure susceptibility at postnatal day 15 (P15; wt, n = 13; Brd2+/-, n = 20), at P30 (wt, n = 20; Brd2+/-, n = 20), and in adulthood (5-6 months of age; wt, n = 10; Brd2+/-, n = 12). We measured latency to clonic and tonic-clonic seizure onset (flurothyl threshold). We also compared relative density of parvalbumin-positive (PVA+) and GAD67+ GABA neurons in the striatum and primary motor (M1) neocortex of P15 (n = 6-13 mice per subgroup) and P30 (n = 7-10 mice per subgroup) mice. Additional neonatal Brd2+/- mice were injected with testosterone propionate (females) or formestane (males) and challenged with flurothyl at P30. RESULTS: P15 Brd2+/- mice showed no difference in seizure susceptibility compared to P15 wt mice. However, even at this early age, Brd2+/- mice showed fewer PVA+ neurons in the striatum and M1 neocortex. Compared to wt, the striatum in Brd2+/- mice showed an increased proportion of immature PVA+ neurons, with smaller cell bodies and limited dendritic arborization. P30 Brd2+/- mice displayed increased susceptibility to flurothyl-induced clonic seizures compared to wt. Both genotype and sex strongly influenced the density of PVA+ neurons in the striatum. Susceptibility to clonic seizures remained increased in adult Brd2+/- mice, and additionally there was increased susceptibility to tonic-clonic seizures. In P30 females, neonatal testosterone reduced the number of flurothyl-induced clonic seizures. SIGNIFICANCE: A decrease in striatal PVA+ GABAergic neurons developmentally precedes the onset of increased seizure susceptibility and likely contributes to the expression of the syndrome.

ACTON PROLONGATUM® suppresses spasms head to head with Acthar® Gel in the model of infantile spasms.

Epileptic spasms during infancy (infantile spasms, IS) are a rare epilepsy syndrome with dire prognosis. Current treatments, effective in about 55% of cases, include hormonal therapy (adrenocorticotropic hormone [ACTH] = adrenocorticotropin or corticosteroids) or vigabatrin (also in combination with hormones). In addition to their limited efficacy, these treatments may also carry serious adverse effects. Thus, the search for new effective drugs to treat this rare disease is desirable. In this study, we determined the efficacy of ACTON PROLONGATUM® (AP; Ferring Pharmaceuticals) in comparison with Acthar® Gel (Mallinckrodt) and full 39 amino-acid rat ACTH molecule (Genscript) in the rodent model of IS consisting of prenatal priming with betamethasone and repeated postnatal trigger of spasms with N-methyl-d-aspartate. Treatment with these ACTH varieties was given on postnatal days (P)12, P13, and P14 in a prospective test (treatment onset on P12 AFTER induction of spasms). Two independent arms were investigated: subcutaneous (SC) and intramuscular (IM) deliveries that were evaluated separately. In the SC arm, there was a significant suppression of the number of spasms after both Acthar® Gel and AP on P13 and P15 compared with gelatin control. In the IM arm, a significant suppression of the number of spasms was achieved only after AP on both P13 and P15 indicating that after IM delivery, Acthar® Gel was not as effective as AP. In this study, we confirmed the efficacy of two ACTH formulations (gelatin-based Acthar® Gel and carboxymethyl cellulose-based AP) in the model of IS. ACTON PROLONGATUM® may become a valuable therapy for IS. In our animal model, AP was at least as efficient as the standard of care, Acthar® Gel.

Reduced Hippocampal Dendrite Branching, Spine Density and Neurocognitive Function in Premature Rabbits, and Reversal with Estrogen or TrkB Agonist Treatment.

Preterm-born children suffer from neurological and behavioral disorders. Herein, we hypothesized that premature birth and non-maternal care of preterm newborns might disrupt neurobehavioral function, hippocampal dendritic arborization, and dendritic spine density. Additionally, we assessed whether 17ß-estradiol (E2) replacement or the TrkB receptor agonist, 7,8-dihydroxyflavone (DHF), would reverse compromised dendritic development and cognitive function in preterm newborns. These hypotheses were tested by comparing preterm (E28.5) rabbit kits cared and gavage-fed by laboratory personnel and term-kits reared and breast-fed by their mother doe at an equivalent postconceptional age. Neurobehavioral tests showed that both premature-birth and formula-feeding with non-maternal care led to increased anxiety behavior, poor social interaction, and lack of novelty preference compared with term-kits. Dendritic branching and number of total or mushroom dendritic spines were reduced in the CA1 field of preterm-kits compared with term controls. While CDC42 and Rac1/2/3 expression levels were lower, RhoA-activity was higher in preterm-kits compared with term controls. Both E2 and DHF treatment reversed prematurity-induced reduction in spine density, reduced total RhoA-GTPase levels, and enhanced cognitive function. Hence, prematurity and non-maternal care result in cognitive deficits, and reduced dendritic arbors and spines in CA1. E2 replacement or DHF treatment might reverse changes in dendritic spines and improve neurodevelopment in premature infants.

Estradiol does not affect spasms in the betamethasone-NMDA rat model of infantile spasms.

OBJECTIVE: This study attempted to validate the effects of neonatal estradiol in ameliorating the spasms in the prenatally betamethasone-primed N-methyl-d-aspartate (NMDA) model of infantile spasms in rats as shown previously in a mouse Arx gene knock-in expansion model of infantile spasms. METHODS: Neonatal rats prenatally exposed to betamethasone (on day 15 of pregnancy) were treated with subcutaneous 40 ng/g estradiol benzoate (EB) between postnatal days (P)3-P10 or P0-P5. A synthetic estrogen analogue, diethylstilbestrol, was used between P0 and P5 (2 µg per rat, s.c.). On P12, P13, and P15, the rats were subjected to NMDA-triggered spasms, and latency to onset and number of spasms were evaluated. Rats with EB on P3-P10 were tested after spasms in the open field, novel object recognition, and elevated plus maze to determine effects of treatment on behavior. Additional rats with P3-P10 or P0-P5 EB were investigated for γ-aminobutyric acid (GABA)ergic neurons (glutamate decarboxylase [GAD]67 expression) in the neocortex. As a positive control, a group of rats received either subcutaneous adrenocorticotropic hormone (ACTH) (2 × 0.3 mg/kg on P12 and 3 × 0.3 mg/kg on P13 and P14) or vehicle after the first episode of spasms on P12. RESULTS: Neither EB treatment nor diethylstilbestrol consistently affected expression of spasms in this model, although we found a significant increase in GAD67-immunopositive cells in the neocortex after P3-P10 and P0-P5 EB treatment, consistent with a study in mice. Behavioral tests showed increase in lateralization in male rats treated with P3-P10 EB, a behavioral trait usually associated with female sex. Diethylstilbestrol treatment in male rats resulted in arrested pubertal descent of testes. ACTH had robust effects in suppressing spasms. SIGNIFICANCE: Treatment of infantile spasms (IS) using neonatal EB may be justified in those cases of IS that present with detectable deficits in GABAergic neurons. In other types of IS, the efficacy of neonatal EB and its analogues is not supported.

Sex and hormonal influences on seizures and epilepsy.

Epilepsy is the third most common chronic neurological disorder. Clinical and experimental evidence supports the role of sex and influence of sex hormones on seizures and epilepsy as well as alterations of the endocrine system and levels of sex hormones by epileptiform activity. Conversely, seizures are sensitive to changes in sex hormone levels, which in turn may affect the seizure-induced neuronal damage. The effects of reproductive hormones on neuronal excitability and seizure-induced damage are complex to contradictory and depend on different mechanisms, which have to be accounted for in data interpretation. Both estradiol and progesterone/allopregnanolone may have beneficial effects for patients with epilepsy. Individualized hormonal therapy should be considered as adjunctive treatment in patients with epilepsy to improve seizure control as well as quality of life.

Altered neurotransmitter release, vesicle recycling and presynaptic structure in the pilocarpine model of temporal lobe epilepsy.

In searching for persistent seizure-induced alterations in brain function that might be causally related to epilepsy, presynaptic transmitter release has relatively been neglected. To measure directly the long-term effects of pilocarpine-induced status epilepticus on vesicular release and recycling in hippocampal mossy fibre presynaptic boutons, we used (i) two-photon imaging of FM1-43 vesicular release in rat hippocampal slices; and (ii) transgenic mice expressing the genetically encoded pH-sensitive fluorescent reporter synaptopHluorin preferentially at glutamatergic synapses. In this study we found that, 1-2 months after pilocarpine-induced status epilepticus, there were significant increases in mossy fibre bouton size, faster rates of action potential-driven vesicular release and endocytosis. We also analysed the ultrastructure of rat mossy fibre boutons using transmission electron microscopy. Pilocarpine-induced status epilepticus led to a significant increase in the number of release sites, active zone length, postsynaptic density area and number of vesicles in the readily releasable and recycling pools, all correlated with increased release probability. Our data show that presynaptic release machinery is persistently altered in structure and function by status epilepticus, which could contribute to the development of the chronic epileptic state and may represent a potential new target for antiepileptic therapies.

Epileptic spasms in infancy: Transferring rat prenatal betamethasone-postnatal NMDA model to mice.

Epileptic spasms during infancy represent a devastating and refractory epilepsy syndrome. To advance studies on mechanisms and treatment using available mouse mutant models, we transferred our validated rat model of epileptic spasms to mice. Initially, we determined sensitivity of C57BL/6J mice to various doses (12-20 mg/kg) of NMDA on postnatal day 11 (P11) and P15. We primed mice with different doses of betamethasone (0.4-2.0 mg/kg) prenatally on gestational day (G)14 or G12 and tested spasms on P11. We also tested 2 different ACTH treatment paradigms (0.3 or 1.0 mg/kg) in prenatally primed as well as naïve mice. Data show that spasms in P11 mice, can be induced with the highest yield after 12 mg/kg dose of NMDA. Prenatal priming on G14 did not modify response to NMDA or sensitize spasms to ACTH. The betamethasone priming on G12 resulted in an increase in the number of NMDA-triggered spasms. Data indicate that the model transfer from rats to mice is non-linear and differences in prenatal brain development, metabolic rates, as well as sensitivity to convulsant drugs have to be considered.

Astrocyte and neuronal Panx1 support long-term reference memory in mice.

Pannexin 1 (Panx1) are ubiquitously expressed proteins that form plasma membrane channels permeable to anions and moderate sized signaling molecules (e.g., ATP, glutamate). In the nervous system, activation of Panx1 channels have been extensively shown to contribute to distinct neurological disorders (epilepsy, chronic pain, migraine, neuroAIDS, etc.) but knowledge of extent to which these channels have a physiological role remains restricted to three studies supporting their involvement in hippocampus dependent learning. Given that Panx1 channels may provide an important mechanism for activity-dependent neuron-glia interaction, we used Panx1 transgenic mice with global and cell-type specific deletions of Panx1 to interrogate their participation in working and reference memory. Using the 8-arm radial maze, we show that long-term spatial reference memory, but not spatial working memory, is deficient in Panx1-null mice and that both astrocyte and neuronal Panx1 contribute to the consolidation of long-term spatial memory. Field potential recordings in hippocampal slices of Panx1-null mice revealed an attenuation of both long-term potentiation (LTP) of synaptic strength and long-term depression (LTD) at Schaffer collateral - CA1 synapses without alterations basal synaptic transmission or pre-synaptic paired-pulse facilitation. Our results implicate both neuronal and astrocyte Panx1 channels as critical players for the development and maintenance of long-term spatial reference memory in mice.

Novel neurosteroid pregnanolone pyroglutamate suppresses neurotoxicity syndrome induced by tetramethylenedisulfotetramine but is ineffective in a rodent model of infantile spasms.

BACKGROUND: Neurosteroids are investigated as effective antidotes for the poisoning induced by tetramethylenedisulfotetramine (TMDT) as well as treatments for epileptic spasms during infancy. Both these conditions are quite resistant to pharmacotherapy; thus, a search for new treatments is warranted. METHODS: In this study, we determined the efficacy of two novel neurosteroids, pregnanolone glutamate (PAG) and pregnanolone pyroglutamate (PPG), and tested these drugs in doses of 1-10 mg/kg (ip) against the TMDT syndrome and in our rodent model of infantile spasms. RESULTS: Only PPG in doses 5 and 10 mg/kg suppressed the severity of the TMDT syndrome and TMDT-induced lethality, while the 1 mg/kg dose was without an effect. Interestingly, the 1 mg/kg dose of PPG in combination with 1 mg/kg of diazepam was also effective against TMDT poisoning. Neither PAG nor PPG were effective against experimental spasms in the N-methyl-D-aspartate (NMDA)-triggered model of infantile spasms. CONCLUSIONS: While evidence suggests that PAG can act through multiple actions which include allosteric inhibition of NMDA-induced and glycine receptor-evoked currents as well as augmentation of É£-aminobutyric acid subtype A (GABAA) receptor-induced currents, the agent appears to neither have the appropriate mechanistic signature for activity in the infantile spasm model, nor the adequate potency, relative to PPG, for ameliorating the TMDT syndrome. The full mechanisms of action of PPG, which may become a potent TMDT antidote either alone or in combination with diazepam are yet unknown and thus require further investigation.

Astrocyte and Neuronal Panx1 Support Long-Term Reference Memory in Mice.

Pannexin 1 (Panx1) is an ubiquitously expressed protein that forms plasma membrane channels permeable to anions and moderate-sized signaling molecules (e.g., ATP, glutamate). In the nervous system, activation of Panx1 channels has been extensively shown to contribute to distinct neurological disorders (epilepsy, chronic pain, migraine, neuroAIDS, etc.), but knowledge of the extent to which these channels have a physiological role remains restricted to three studies supporting their involvement in hippocampus dependent learning. Given that Panx1 channels may provide an important mechanism for activity-dependent neuron-glia interaction, we used Panx1 transgenic mice with global and cell-type specific deletions of Panx1 to interrogate their participation in working and reference memory. Using the eight-arm radial maze, we show that long-term spatial reference memory, but not spatial working memory, is deficient in Panx1-null mice and that both astrocyte and neuronal Panx1 contribute to the consolidation of long-term spatial memory. Field potential recordings in hippocampal slices of Panx1-null mice revealed an attenuation of both long-term potentiation (LTP) of synaptic strength and long-term depression (LTD) at Schaffer collateral-CA1 synapses without alterations of basal synaptic transmission or pre-synaptic paired-pulse facilitation. Our results implicate both neuronal and astrocyte Panx1 channels as critical players for the development and maintenance of long-term spatial reference memory in mice.

Human cortical interneurons optimized for grafting specifically integrate, abort seizures, and display prolonged efficacy without over-inhibition.

Previously, we demonstrated the efficacy of human pluripotent stem cell (hPSC)-derived GABAergic cortical interneuron (cIN) grafts in ameliorating seizures. However, a safe and reliable clinical translation requires a mechanistic understanding of graft function, as well as the assurance of long-term efficacy and safety. By employing hPSC-derived chemically matured migratory cINs in two models of epilepsy, we demonstrate lasting efficacy in treating seizures and comorbid deficits, as well as safety without uncontrolled growth. Host inhibition does not increase with increasing grafted cIN densities, assuring their safety without the risk of over-inhibition. Furthermore, their closed-loop optogenetic activation aborted seizure activity, revealing mechanisms of graft-mediated seizure control and allowing graft modulation for optimal translation. Monosynaptic tracing shows their extensive and specific synaptic connections with host neurons, resembling developmental connection specificity. These results offer confidence in stem cell-based therapy for epilepsy as a safe and reliable treatment for patients suffering from intractable epilepsy.

Differential antagonism of tetramethylenedisulfotetramine-induced seizures by agents acting at NMDA and GABA(A) receptors.

Tetramethylenedisulfotetramine (TMDT) is a highly lethal neuroactive rodenticide responsible for many accidental and intentional poisonings in mainland China. Ease of synthesis, water solubility, potency, and difficulty to treat make TMDT a potential weapon for terrorist activity. We characterized TMDT-induced convulsions and mortality in male C57BL/6 mice. TMDT (ip) produced a continuum of twitches, clonic, and tonic-clonic seizures decreasing in onset latency and increasing in severity with increasing dose; 0.4mg/kg was 100% lethal. The NMDA antagonist, ketamine (35mg/kg) injected ip immediately after the first TMDT-induced seizure, did not change number of tonic-clonic seizures or lethality, but increased the number of clonic seizures. Doubling the ketamine dose decreased tonic-clonic seizures and eliminated lethality through a 60min observation period. Treating mice with another NMDA antagonist, MK-801, 0.5 or 1mg/kg ip, showed similar effects as low and high doses of ketamine, respectively, and prevented lethality, converting status epilepticus EEG activity to isolated interictal discharges. Treatment with these agents 15min prior to TMDT administration did not increase their effectiveness. Post-treatment with the GABA(A) receptor allosteric enhancer diazepam (5mg/kg) greatly reduced seizure manifestations and prevented lethality 60min post-TMDT, but ictal events were evident in EEG recordings and, hours post-treatment, mice experienced status epilepticus and died. Thus, TMDT is a highly potent and lethal convulsant for which single-dose benzodiazepine treatment is inadequate in managing electrographic seizures or lethality. Repeated benzodiazepine dosing or combined application of benzodiazepines and NMDA receptor antagonists is more likely to be effective in treating TMDT poisoning.

Prenatal stress promotes development of spasms in infant rats.

We have developed a new model of cryptogenic infantile spasms with prenatal betamethasone brain priming to increase susceptibility to development-specific spasms triggered by N-methyl-d-aspartate (NMDA). A recent clinical study linked severe prenatal stress to increased risk for development of infantile spasms. Here, we determined whether prenatal restraint stress (2 × 45 min) in rats on gestational day 15 would increase susceptibility to develop spasms on postnatal day 15. Prenatal stress significantly accelerated onset and increased number of NMDA-triggered spasms compared to handled controls. A single adrenocorticotropic hormone (ACTH or corticotropin) dose delivered acutely had no effects, whereas long-term (3 day) ACTH pretreatment significantly increased latency to onset and decreased number of spasms (an effect similar to that in the human condition). Our data support the notion that extra care should be provided during pregnancy to minimize stress.

Rapamycin has age-, treatment paradigm-, and model-specific anticonvulsant effects and modulates neuropeptide Y expression in rats.

PURPOSE: Rapamycin (RAP) has certain antiepileptogenic features. However, it is unclear whether these effects can be explained by the anticonvulsant action of RAP, which has not been studied. To address this question, we tested potential anticonvulsant effects of RAP in immature and adult rats using different seizure models and treatment paradigms. In addition, we studied changes in the expression of neuropeptide Y (NPY) induced by RAP, which may serve as an indirect target of the RAP action. METHODS: A complex approach was adopted to evaluate the anticonvulsant potential of RAP: We used flurothyl-, pentylenetetrazole (PTZ)-, N-methyl-D-aspartate (NMDA)-, and kainic acid (KA)-induced seizures to test the effects of RAP using different pretreatment protocols in immature and adult rats. We also evaluated expression of NPY within the primary motor cortex, hippocampal CA1, and dentate gyrus (DG) after different pretreatments with RAP in immature rats. KEY FINDINGS: We found the following: (1) RAP administered with short-term pretreatment paradigms has a weak anticonvulsant potential in the seizure models with compromised inhibition. (2) Lack of RAP efficacy correlates with decreased NPY expression in the cortex, CA1, and DG. Specifically in immature rats, a single dose of RAP (3 mg/kg) 4 or 24 h before seizure testing had anticonvulsant effects against PTZ-induced seizures. In the flurothyl seizure model only the 4-h pretreatment with RAP was anticonvulsant in the both age groups. Short-term pretreatments with RAP had no effects against NMDA- and KA-induced seizures tested in immature rats. Long-term pretreatments with RAP over 8 days did not show beneficial effect in all tested seizure models in developing rats. Moreover, the long-term pretreatment with RAP had a slight proconvulsant effect on KA-induced seizures. In immature rats, any lack of anticonvulsant effect (including proconvulsant effect of multiple doses of RAP) was associated with downregulation of NPY expression in the cortex and DG. In immature animals, after a single dose of RAP with 24 h delay, we found a decrease of NPY expression in DG, and CA1 as well. SIGNIFICANCE: Our data show weak age-, treatment paradigm-, and model-specific anticonvulsant effects of RAP as well as loss of those effects after long-term RAP pretreatment associated with downregulation of NPY expression. These findings suggest that RAP is a poor anticonvulsant and may have beneficial effects only against epileptogenesis. In addition, our data present new insights into mechanisms of RAP action on seizures indicating a possible connection between mammalian target of rapamycin (mTOR) signaling and NPY system.

Validation of the rat model of cryptogenic infantile spasms.

PURPOSE: To determine whether a new model of cryptogenic infantile spasms consisting of prenatal priming with betamethasone and postnatal trigger of spasms by N-methyl-D-aspartate (NMDA) responds to chronic adrenocorticotropic hormone (ACTH) treatment, and has electroencephalography (EEG) signature, efficacy of treatments, and behavioral impairments similar to those in human infantile spasms. METHODS: Rats prenatally primed with betamethasone on gestational day 15 were used. Spasms were triggered with NMDA between postnatal days (P) 10 and 15 in a single session or in multiple sessions in one subject. The expression of spasms was compared to prenatally saline-injected controls. Effects of relevant treatments (ACTH, vigabatrin, methylprednisolone, rapamycin) were determined in betamethasone-primed rats. In the rats after spasms, behavioral evaluation was performed in the open field and elevated plus maze on P20-22. KEY FINDINGS: NMDA at P10-15 (the rat "infant" period) triggers the spasms significantly earlier and in greater numbers in the prenatal betamethasone-exposed brain compared to controls. Similar to human condition, the spasms occur in clusters. Repeated trigger of spasms is associated with ictal EEG electrodecrements and interictal large-amplitude waves, a possible rat variant of hypsarrhythmia. Chronic ACTH treatment in a randomized experiment, and chronic pretreatment with methylprednisolone significantly suppress the number of spasms similar to the human condition. Pretreatment with vigabatrin, but not rapamycin, suppressed the spasms. Significant behavioral changes occurred following multiple bouts of spasms. SIGNIFICANCE: The model of infantile spasms has remarkable similarities with the human condition in semiology, EEG, pharmacologic response, and long-term outcome. Therefore, the model can be used to search for novel and more effective treatments for infantile spasms.

The Contribution of Astrocyte and Neuronal Panx1 to Seizures Is Model and Brain Region Dependent.

Pannexin1 (Panx1) is an ATP release channel expressed in neurons and astrocytes that plays important roles in CNS physiology and pathology. Evidence for the involvement of Panx1 in seizures includes the reduction of epileptiform activity and ictal discharges following Panx1 channel blockade or deletion. However, very little is known about the relative contribution of astrocyte and neuronal Panx1 channels to hyperexcitability. To this end, mice with global and cell type specific deletion of Panx1 were used in one in vivo and two in vitro seizure models. In the low-Mg2+in vitro model, global deletion but not cell-type specific deletion of Panx1 reduced the frequency of epileptiform discharges. This reduced frequency of discharges did not impact the overall power spectra obtained from local field potentials. In the in vitro KA model, in contrast, global or cell type specific deletion of Panx1 did not affect the frequency of discharges, but reduced the overall power spectra. EEG recordings following KA-injection in vivo revealed that although global deletion of Panx1 did not affect the onset of status epilepticus (SE), SE onset was delayed in mice lacking neuronal Panx1 and accelerated in mice lacking astrocyte Panx1. EEG power spectral analysis disclosed a Panx1-dependent cortical region effect; while in the occipital region, overall spectral power was reduced in all three Panx1 genotypes; in the frontal cortex, the overall power was not affected by deletion of Panx1. Together, our results show that the contribution of Panx1 to ictal activity is model, cell-type and brain region dependent.

Females, their estrogens, and seizures.

Estrogens are essential for normal brain functions. The effects of estrogens on seizures are contradictory. More studies are necessary to determine under which conditions the estrogens have proconvulsant effects and when the estrogens may have beneficial action in patients with epilepsy.