RESUMO
Excessive and uncontrolled consumption of alcohol can cause alcohol use disorder (AUD), but its pharmacological mechanisms are not fully understood. Inhibiting the reverse mode activity of the sodium-calcium exchanger (NCX) can reduce the risk of alcohol withdrawal seizures, suggesting that NCX could play a role in controlling alcohol consumption. Here, we investigated how two potent inhibitors of NCX reverse mode activity, SN-6 (NCX1) and KB-R7943 (NCX3), affect voluntary alcohol consumption in adult male and female rats using the intermittent alcohol access two-bottle choice paradigm. Initially, animals were trained to drink 7.5% ethanol and water for four weeks before administering SN-6 and KB-R7934. Afterward, their alcohol intake, preference, and water intake were recorded 2 and 24 h after exposure to water and 7.5% ethanol. SN-6 significantly reduced alcohol consumption by 48% in male and 36% in female rats without affecting their water intake. Additionally, SN-6 significantly reduced alcohol preference in females by 27%. However, KB-R7943 reduced alcohol consumption by 42% in female rats and did not affect alcohol preference or water intake. These findings suggest that alcohol exposure increased NCX reverse activity, and targeting NCX1 could be an effective strategy for reducing alcohol consumption in subjects susceptible to withdrawal seizures.
Assuntos
Alcoolismo , Síndrome de Abstinência a Substâncias , Tioureia/análogos & derivados , Humanos , Adulto , Feminino , Masculino , Animais , Ratos , Trocador de Sódio e Cálcio , Consumo de Bebidas Alcoólicas , Etanol , ÁguaRESUMO
Three decades of studies have shown that inhibition of the substantia nigra pars reticulata (SNpr) attenuates seizures, yet the circuits mediating this effect remain obscure. SNpr projects to the deep and intermediate layers of the superior colliculus (DLSC) and the pedunculopontine nucleus (PPN), but the contributions of these projections are unknown. To address this gap, we optogenetically silenced cell bodies within SNpr, nigrotectal terminals within DLSC, and nigrotegmental terminals within PPN. Inhibition of cell bodies in SNpr suppressed generalized seizures evoked by pentylenetetrazole (PTZ), partial seizures evoked from the forebrain, absence seizures evoked by gamma-butyrolactone (GBL), and audiogenic seizures in genetically epilepsy-prone rats. Strikingly, these effects were fully recapitulated by silencing nigrotectal projections. By contrast, silencing nigrotegmental terminals reduced only absence seizures and exacerbated seizures evoked by PTZ. These data underscore the broad-spectrum anticonvulsant efficacy of this circuit, and demonstrate that specific efferent projection pathways differentially control different seizure types.
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Acoustically evoked seizures (e.g., audiogenic seizures or AGS) are common in models of inherited epilepsy and occur in a variety of species including rat, mouse, and hamster. Two models that have been particularly well studied are the genetically epilepsy prone rat (GEPR-3) and the Wistar Audiogenic Rat (WAR) strains. Acute and repeated AGS, as well as comorbid conditions, displays a close phenotypic overlap in these models. Whether these similarities arise from convergent or divergent structural changes in the brain remains unknown. Here, we examined the brain structure of Sprague Dawley (SD) and Wistar (WIS) rats, and quantified changes in the GEPR-3 and WAR, respectively. Brains from adult, male rats of each strain (n=8-10 per group) were collected, fixed, and embedded in agar and imaged using a 7 tesla Bruker MRI. Post-acquisition analysis included voxel-based morphometry (VBM), diffusion tensor imaging (DTI), and manual volumetric tracing. In the VBM analysis, GEPR-3 displayed volumetric changes in brainstem structures known to be engaged by AGS (e.g., superior and inferior colliculus, periaqueductal grey) and in forebrain structures (e.g., striatum, septum, nucleus accumbens). WAR displayed volumetric changes in superior colliculus, and a broader set of limbic regions (e.g., hippocampus, amygdala/piriform cortex). The only area of significant overlap in the two strains was the midline cerebellum: both GEPR-3 and WAR showed decreased volume compared to their control strains. In the DTI analysis, GEPR-3 displayed decreased fractional anisotropy (FA) in the corpus callosum, posterior commissure and commissure of the inferior colliculus (IC). WAR displayed increased FA only in the commissure of IC. These data provide a biological basis for further comparative and mechanistic studies in the GEPR-3 and WAR models, as well as provide additional insight into commonalities in the pathways underlying AGS susceptibility and behavioral comorbidity.
Assuntos
Encéfalo/diagnóstico por imagem , Epilepsia/diagnóstico por imagem , Imageamento por Ressonância Magnética , Ratos Sprague-Dawley , Ratos Wistar , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Epilepsia/patologia , Processamento de Imagem Assistida por Computador , Masculino , Tamanho do Órgão , Fenótipo , Especificidade da EspécieRESUMO
Voltage-sensitive Ca2+ (CaV) channels are the primary route of depolarization-induced Ca2+ entry in neurons and other excitable cells, leading to an increase in intracellular Ca2+ concentration ([Ca2+]i). The resulting increase in [Ca2+]i activates a wide range of Ca2+-dependent processes in neurons, including neurotransmitter release, gene transcription, activation of Ca2+-dependent enzymes, and activation of certain K+ channels and chloride channels. In addition to their key roles under physiological conditions, CaV channels are also an important target of alcohol, and alcohol-induced changes in Ca2+ signaling can disturb neuronal homeostasis, Ca2+-mediated gene transcription, and the function of neuronal circuits, leading to various neurological and/or neuropsychiatric symptoms and disorders, including alcohol withdrawal induced-seizures and alcoholism.
Assuntos
Intoxicação Alcoólica/fisiopatologia , Encéfalo/fisiopatologia , Canais de Cálcio/fisiologia , Sinalização do Cálcio , Síndrome de Abstinência a Substâncias/fisiopatologia , Cálcio , Etanol , Humanos , NeurôniosRESUMO
Because sites of seizure origin may be unknown or multifocal, identifying targets from which activation can suppress seizures originating in diverse networks is essential. We evaluated the ability of optogenetic activation of the deep/intermediate layers of the superior colliculus (DLSC) to fill this role. Optogenetic activation of DLSC suppressed behavioral and electrographic seizures in the pentylenetetrazole (forebrain+brainstem seizures) and Area Tempestas (forebrain/complex partial seizures) models; this effect was specific to activation of DLSC, and not neighboring structures. DLSC activation likewise attenuated seizures evoked by gamma butyrolactone (thalamocortical/absence seizures), or acoustic stimulation of genetically epilepsy prone rates (brainstem seizures). Anticonvulsant effects were seen with stimulation frequencies as low as 5 Hz. Unlike previous applications of optogenetics for the control of seizures, activation of DLSC exerted broad-spectrum anticonvulsant actions, attenuating seizures originating in diverse and distal brain networks. These data indicate that DLSC is a promising target for optogenetic control of epilepsy.
Assuntos
Epilepsia/fisiopatologia , Epilepsia/terapia , Neurônios/fisiologia , Optogenética/métodos , Colículos Superiores/fisiopatologia , 4-Butirolactona , Estimulação Acústica , Animais , Tronco Encefálico/fisiopatologia , Modelos Animais de Doenças , Eletrocorticografia , Masculino , Pentilenotetrazol , Prosencéfalo/fisiopatologia , Ratos Sprague-Dawley , Tálamo/fisiopatologiaRESUMO
BACKGROUND: Cyclic AMP-dependent protein kinase A (PKA) signaling is a key target for the action of alcohol and may therefore play a role in the pathophysiology of alcohol withdrawal seizures (AWSs). Here, we investigated the role of PKA activity with respect to increased seizure susceptibility in rats that were subjected to alcohol withdrawal. METHODS: Adult male Sprague Dawley rats received 3 daily doses of ethanol (EtOH) (or vehicle) for 4 consecutive days. Rats were then tested for susceptibility to acoustically evoked AWSs 3, 24, and 48 hours after the last alcohol dose. In separate experiments, the inferior colliculus (IC) was collected at these same time points from rats subjected to alcohol withdrawal and control rats following alcohol withdrawal. PKA activity, catalytic Cα (PKACα ) protein, regulatory RIIα (PKARIIα ) protein, and RIIß (PKARIIß ) protein were measured in the IC. Lastly, in situ pharmacological studies were performed to evaluate whether inhibiting PKA activity in the IC suppressed AWSs. RESULTS: In the EtOH-treated group, AWSs were observed at the 24-hour time point, but not at the 3-hour or 48-hour time points. In the IC, PKA activity was significantly higher both 3 hours (i.e., before AWS susceptibility) and 24 hours after the last alcohol dose (when AWS susceptibility peaked) than in control rats. Consistent with these findings, protein levels of the PKACα subunit were significantly increased in the IC both 3 and 24 hours after the last alcohol dose. Lastly, in situ inhibition of PKA activity within the IC suppressed AWSs. CONCLUSIONS: The increase in PKA activity and PKACα protein expression in the IC preceded the occurrence of AWSs, and inhibiting PKA activity within the IC suppressed acoustically evoked AWSs. Together, these findings suggest that altered PKA activity plays a key role in the pathogenesis of AWSs.
Assuntos
Convulsões por Abstinência de Álcool/enzimologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Colículos Inferiores/enzimologia , Convulsões por Abstinência de Álcool/sangue , Intoxicação Alcoólica/psicologia , Animais , Concentração Alcoólica no Sangue , Peso Corporal , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Masculino , Distribuição Aleatória , Ratos Sprague-DawleyRESUMO
BACKGROUND: We previously reported increased current density through L-type voltage-gated Ca(2+) (CaV1) channels in inferior colliculus (IC) neurons during alcohol withdrawal. However, the molecular correlate of this increased CaV1 current is currently unknown. METHODS: Rats received three daily doses of ethanol every 8 hours for 4 consecutive days; control rats received vehicle. The IC was dissected at various time intervals following alcohol withdrawal, and the mRNA and protein levels of the CaV1.3 and CaV1.2 α1 subunits were measured. In separate experiments, rats were tested for their susceptibility to alcohol withdrawal-induced seizures (AWS) 3, 24, and 48 hours after alcohol withdrawal. RESULTS: In the alcohol-treated group, AWS were observed 24 hours after withdrawal; no seizures were observed at 3 or 48 hours. No seizures were observed at any time in the control-treated rats. Compared to control-treated rats, the mRNA level of the CaV1.3 α1 subunit was increased 1.4-fold, 1.9-fold, and 1.3-fold at 3, 24, and 48 hours, respectively. In contrast, the mRNA level of the CaV1.2 α1 subunit increased 1.5-fold and 1.4-fold at 24 and 48 hours, respectively. At 24 hours, Western blot analyses revealed that the levels of the CaV1.3 and CaV1.2 α1 subunits increased by 52% and 32%, respectively, 24 hours after alcohol withdrawal. In contrast, the CaV1.2 and CaV1.3 α1 subunits were not altered at either 3 or 48 hours during alcohol withdrawal. CONCLUSIONS: Expression of the CaV1.3 α1 subunit increased in parallel with AWS development, suggesting that altered L-type CaV1.3 channel expression is an important feature of AWS pathogenesis.
Assuntos
Convulsões por Abstinência de Álcool/metabolismo , Canais de Cálcio Tipo L/genética , Etanol/toxicidade , Colículos Inferiores/citologia , Neurônios/metabolismo , Convulsões por Abstinência de Álcool/induzido quimicamente , Animais , Canais de Cálcio/genética , Canais de Cálcio Tipo L/classificação , Depressores do Sistema Nervoso Central/administração & dosagem , Depressores do Sistema Nervoso Central/toxicidade , Etanol/administração & dosagem , Colículos Inferiores/efeitos dos fármacos , Masculino , RNA Mensageiro/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Fatores de Tempo , Regulação para Cima/efeitos dos fármacosRESUMO
BACKGROUND: The link between epilepsy and alcohol consumption is complex, with conflicting reports. To enhance our understanding of this link, we conducted a study to determine how inherited seizure susceptibility affects voluntary alcohol consumption and influences alcohol withdrawal seizures in male and female genetically epilepsy-prone rats (GEPR-3s) compared to Sprague Dawley (SD) rats. METHODS: In the first experiment, animals were given access to two bottles simultaneously, one containing water and the other 7.5%, 15%, or 30% (v/v) alcohol three times a week for each dose after acclimation to drinking water. In a second experiment, animals were tested for acoustically evoked alcohol seizures 24 h after the last session of voluntary alcohol consumption. RESULTS: Analysis revealed that GEPR-3s (males and females) had lower alcohol intake and preference than SD rats, particularly at lower alcohol concentrations. However, female GEPR-3s consumed more alcohol and had a higher alcohol preference than males. Furthermore, withdrawal from voluntary alcohol consumption facilitated the onset and duration of seizures in GEPR-3s. CONCLUSIONS: Our study suggests that genetic seizure susceptibility in GEPR-3s is negatively associated with alcohol consumption. However, withdrawal from low to moderate amounts of alcohol intake can promote epileptogenesis in the epileptic GEPR-3s.
RESUMO
Transient receptor potential canonical 3 (TRPC3) channels are important in regulating Ca2+ homeostasis and have been implicated in the pathophysiology of chemically induced seizures. Inherited seizure susceptibility in genetically epilepsy-prone rats (GEPR-3s) has been linked to increased voltage-gated Ca2+ channel currents in the inferior colliculus neurons, which can affect intraneuronal Ca2+ homeostasis. However, whether TRPC3 channels also contribute to inherited seizure susceptibility in GEPR-3s is unclear. This study investigated the effects of JW-65, a potent and selective inhibitor of TRPC3 channels, on acoustically evoked seizure susceptibility in adult male and female GEPR-3s. These seizures consisted of wild running seizures (WRSs) that evolved into generalized tonic-clonic seizures (GTCSs). The results showed that acute administration of low doses of JW-65 significantly decreased by 55-89% the occurrence of WRSs and GTCSs and the seizure severity in both male and female GEPR-3s. This antiseizure effect was accompanied by increased seizure latency and decreased seizure duration. Additionally, female GEPR-3s were more responsive to JW-65's antiseizure effects than males. Moreover, JW-65 treatment for five consecutive days completely suppressed acoustically evoked seizures in male and female GEPR-3s. These findings suggest that inhibiting TRPC3 channels could be a promising antiseizure strategy targeting Ca2+ signaling mechanisms in inherited generalized tonic-clonic epilepsy.
Assuntos
Convulsões , Canais de Cátion TRPC , Animais , Masculino , Feminino , Convulsões/fisiopatologia , Convulsões/genética , Convulsões/induzido quimicamente , Ratos , Canais de Cátion TRPC/antagonistas & inibidores , Canais de Cátion TRPC/genética , Anticonvulsivantes/farmacologia , Anticonvulsivantes/uso terapêutico , Predisposição Genética para Doença , Epilepsia/fisiopatologia , Epilepsia/genética , Epilepsia/induzido quimicamente , Epilepsia/tratamento farmacológicoRESUMO
INTRODUCTION: Epilepsies are disorders of neuronal excitability characterized by spontaneously recurrent focal and generalized seizures, some of which result from genetic mutations. Despite the availability of antiseizure medications, pharmaco-resistant epilepsy is seen in about 23% of epileptic patients worldwide. Therefore, there is an urgent need to develop novel therapeutic strategies for epilepsies. Several epilepsy-associated genes have been found in humans. Seizure susceptibility can also be induced in Drosophila mutants, some showing features resembling human epilepsies. Interestingly, several second-site mutation gene products have been found to suppress seizure susceptibility in the seizure genetic model Drosophila. Thus, these so-called 'seizure-suppressor' gene variants may lead to developing a novel class of antiseizure medications. AREA COVERED: This review evaluates the potential therapeutic of seizure-suppressor gene variants. EXPERT OPINION: Studies on epilepsy-associated genes have allowed analyses of mutations linked to human epilepsy by reproducing these mutations in Drosophila using reverse genetics to generate potential antiseizure therapeutics. As a result, about fifteen seizure-suppressor gene mutants have been identified. Furthermore, some of these epilepsy gene mutations affect ligand-and voltage-gated ion channels. Therefore, a better understanding of the antiseizure activity of seizure-suppressor genes is essential in advancing gene therapy and precision medicine for epilepsy.
Assuntos
Epilepsia , Genes Supressores , Animais , Humanos , Epilepsia/tratamento farmacológico , Epilepsia/genética , Convulsões/tratamento farmacológico , Convulsões/genética , Mutação , Drosophila/genéticaRESUMO
The inferior colliculus (IC) is critical in initiating acoustically evoked alcohol withdrawal-induced seizures (AWSs). Recently, we reported that systemic inhibition of Ca2+ entry via the reverse mode activity of the Na+/Ca2+ exchanger (NCXrev) suppressed AWSs, suggesting remodeling of NCX expression and function, at least in the IC, the site of AWS initiation. Here, we probe putative changes in protein expression in the IC of NCX isoforms, including NCX type 1 (NCX1), 2 (NCX2), and 3 (NCX3). We also evaluated the efficacy of targeted inhibition of NCX1rev and NCX3rev activity in the IC on the occurrence and severity of AWSs using SN-6 and KB-R943, respectively. We used our well-characterized alcohol intoxication/withdrawal model associated with enhanced AWS susceptibility. IC tissues from the alcohol-treated group were collected 3 h (before the onset of AWS susceptibility), 24 h (when AWS susceptibility is maximal), and 48 h (when AWS susceptibility is resolved) following alcohol withdrawal; in comparison, IC tissues from the control-treated group were collected at 24 h after the last gavage. Analysis shows that NCX1 protein levels were markedly higher 3 and 24 h following alcohol withdrawal. However, NCX3 protein levels were only higher 3 h following alcohol withdrawal. The analysis also reveals that bilateral microinjections of SN-6 (but not KB-R7943) within the IC markedly suppressed the occurrence and severity of AWSs. Together, these findings indicate that NCX1 is a novel molecular target that may play an essential role in the pathogenesis and pathophysiology of AWSs.
Assuntos
Convulsões por Abstinência de Álcool , Alcoolismo , Colículos Inferiores , Síndrome de Abstinência a Substâncias , Ratos , Animais , Convulsões por Abstinência de Álcool/metabolismo , Colículos Inferiores/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Cálcio/metabolismoRESUMO
BACKGROUND: Cannabidiol (CBD) has been of rapidly growing interest in the epilepsy research field due to its antiseizure properties in preclinical models and patients with pharmacoresistant epilepsy. However, little is known about CBD effects in genetic models of epilepsies. Here we assessed CBD dose-response effects in the Genetically Epilepsy Prone Rats (GEPR-3) strain, which exhibits two types of epileptic seizures, brainstem-dependent generalized tonic-clonic seizures and limbic seizures. METHODS: GEPR-3 s were submitted to the audiogenic seizure (AGS) protocol. Acute AGS are brainstem-dependent generalized tonic-clonic, while repeated AGS (or audiogenic kindling, AK), an epileptogenic process, leads to increased AGS severity and limbic seizure expression. Therefore, two different dose-response studies were performed, one for generalized tonic-clonic seizures and the other for limbic seizures. CBD time-course effects were assessed 2, 4, and 6 h after drug injection. GEPR-3 s were submitted to within-subject tests, receiving intraperitoneal injections of CBD (1, 10, 50, 100 mg/kg/ml) and vehicle. RESULTS: CBD dose-dependently attenuated generalized tonic-clonic seizures in GEPR-3 s; CBD 50 and 100 mg/kg reduced brainstem-dependent seizure severity and duration. In fully kindled GEPR-3 s, CBD 10 mg/kg reduced limbic seizure severity and suppressed limbic seizure expression in 75% of animals. CONCLUSIONS: CBD was effective against brainstem and limbic seizures in the GEPR-3 s. These results support the use of CBD treatment for epilepsies by adding new information about the pharmacological efficacy of CBD in suppressing inherited seizure susceptibility in the GEPR-3 s.
Assuntos
Canabidiol , Epilepsia Reflexa , Excitação Neurológica , Ratos , Animais , Canabidiol/farmacologia , Convulsões/tratamento farmacológico , Excitação Neurológica/fisiologia , Epilepsia Reflexa/tratamento farmacológico , Epilepsia Reflexa/genética , Tronco Encefálico , Niacinamida/farmacologia , Estimulação Acústica , Modelos Animais de DoençasRESUMO
The Biomedicines Special Issue (BSI) of "Pathogenesis and Targeted Therapy of Epilepsy" seeks papers providing new insights into the roles of voltage-gated and ligand-gated ion channels and their related signaling in the pathogenesis and pathophysiology of acquired epilepsy and inherited epilepsy [...].
RESUMO
Inherited seizure susceptibility in genetically epilepsy-prone rats (GEPR-3s) is associated with increased voltage-gated calcium channel currents suggesting a massive calcium influx resulting in increased levels of intraneuronal calcium. Cytosolic calcium, in turn, activates many processes, including chloride channels, to restore normal membrane excitability and limit repetitive firing of the neurons. Here we used EACT and T16Ainh-A01, potent activator and inhibitor of calcium-activated channels transmembrane protein 16A (TMEM16A), respectively, to probe the role of these channels in the pathophysiology of acoustically evoked seizures in the GEPR-3s. We used adult male and female GEPR-3s. Acoustically evoked seizures consisted of wild running seizures (WRSs) that evolved into generalized tonic-clonic seizures (GTCSs) and eventually culminated into forelimb extension (partial tonic seizures). We found that acute EACT treatment at relatively higher tested doses significantly reduced the incidences of WRSs and GTCSs, and the seizure severity in male GEPR-3s. Furthermore, these antiseizure effects were associated with delayed seizure onset and reduced seizure duration. Interestingly, the inhibition of TMEM16A channels reversed EACT's antiseizure effects on seizure latency and seizure duration. No notable antiseizure effects were observed in female GEPR-3s. Together, these findings suggest that activation of TMEM16A channels may represent a putative novel cellular mechanism for suppressing GTCSs.
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Calcium influx plays important roles in the pathophysiology of seizures, including acoustically evoked alcohol withdrawal-induced seizures (AWSs). One Ca2+ influx route of interest is the Na+/Ca2+ exchanger (NCX) that, when operating in its reverse mode (NCXrev) activity, can facilitate Ca2+ entry into neurons, possibly increasing neuronal excitability that leads to enhanced seizure susceptibility. Here, we probed the involvement of NCXrev activity on AWS susceptibility by quantifying the effects of SN-6 and KB-R7943, potent blockers of isoform type 1 (NCX1rev) and 3 (NCX3rev), respectively. Male, adult Sprague-Dawley rats were used. Acoustically evoked AWSs consisted of wild running seizures (WRSs) that evolved into generalized tonic-clonic seizures (GTCSs). Quantification shows that acute SN-6 treatment at a relatively low dose suppressed the occurrence of the GTCSs (but not WRSs) component of AWSs and markedly reduced the seizure severity. However, administration of KB-R7943 at a relatively high dose only reduced the incidence of GTCSs. These findings demonstrate that inhibition of NCX1rev activity is a putative mechanism for the suppression of alcohol withdrawal-induced GTCSs.
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The WAG/Rij strain of rats is commonly used as a preclinical model of genetic absence epilepsy. While widely utilized, the developmental trajectory of absence seizure expression has been only partially described. Moreover, sex differences in this strain have been under-explored. Here, we longitudinally monitored male and female WAG/Rij rats to quantify cortical spike-and-wave discharges (SWDs) monthly, from 4 to 10 months of age. In both male and female WAG/Rij rats, absence seizure susceptibility increased with age. In contrast to previous reports, we found a robust and consistent increase in absence epilepsy susceptibility in male WAG/Rij rats in comparison to females across months. The increased absence seizure susceptibility was characterized by increased number and duration of SWDs, and consequently increased total SWDs duration. These findings highlight a previously un-recognized sex difference in a model of absence epilepsy and narrow the knowledge gap of age-dependent expression of SWDs in the WAG/Rij strain.
Assuntos
Epilepsia Tipo Ausência , Animais , Modelos Animais de Doenças , Eletroencefalografia , Epilepsia Tipo Ausência/genética , Feminino , Masculino , Ratos , Ratos Wistar , Convulsões/genéticaRESUMO
Small conductance calcium-activated potassium (SK) channels dampen neuronal excitability by contributing to slow afterhyperpolarization (AHP) that follows a series of action potentials, and therefore may represent an intrinsic inhibitory mechanism to prevent seizures. We have previously reported that susceptibility to acoustically evoked seizures was associated with downregulation of SK1 and SK3 subtypes of SK channels in the inferior colliculus of the moderated seizure severity strain of the genetically epilepsy-prone rats (GEPR-3s). Here, we evaluated the effects of 1-ethyl-2-benzimidazolinone (1-EBIO), a potent activator of SK channels, on acoustically evoked seizures in both male and female adult GEPR-3s at various time points post-treatment. Systemic administration of 1-EBIO at various tested doses suppressed seizure susceptibility in both male and female GEPR-3s; however, the complete seizure suppression was only observed following administration of relatively higher doses of 1-EBIO in females. These findings indicate that activation of SK channels results in anticonvulsive action against generalized tonic-clonic seizures in both male and female GEPR-3s, with males exhibiting higher sensitivity than females.
Assuntos
Benzimidazóis/farmacologia , Epilepsia/genética , Convulsões/tratamento farmacológico , Canais de Potássio Ativados por Cálcio de Condutância Baixa/agonistas , Potenciais de Ação , Animais , Feminino , Masculino , Ratos , Canais de Potássio Ativados por Cálcio de Condutância Baixa/metabolismoRESUMO
Cannabinoid (CB) receptor agonists are of growing interest as targets for anti-seizure therapies. Here we examined the effect of systemic administration of the CB receptor agonist WIN 55,212-2 (WIN) against audiogenic seizures (AGSs) in the Genetically Epilepsy Prone Rat (GEPR)-3 strain, and against seizures evoked focally from the Area Tempestas (AT). We compared these results to the effect of focal administration of the CB1/2 receptor agonist CP 55940 into the deep layers of the superior colliculus (DLSC), a brain site expressing CB1 receptors. While systemic administration of WIN dose-dependently decreased AGS in GEPR-3s, it was without effect in the AT model. By contrast, intra-DLSC infusion of CP 55940 decreased seizures in both models. To determine if the effects of systemic WIN were dependent upon activation of CB1 receptors in the DSLC, we next microinjected the CB1 receptor antagonist SR141716, before WIN systemic treatment, and tested animals for AGS susceptibility. The pretreatment of the DLSC with SR141716 was without effect on its own and did not alter the anti-convulsant action of WIN systemic administration. Thus, while CB receptors in the DLSC are a potential site of anticonvulsant action, they are not necessary for the effects of systemically administered CB agonists.
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We have previously reported that prenatal alcohol exposure (PAE) in the 2nd trimester-equivalent of gestation is associated with increased N-methyl-d-aspartate (NMDA)-induced generalized tonic-clonic seizures (GTCSs) prevalence in postpartum developing rats. Whether the 1st trimester-equivalent of gestation is also a vulnerable period for developing GTCSs following PAE is unknown. Here, we investigated the effects of a single episode of PAE at embryonic day 8 (E8, in the 1st trimester-equivalent) or E18 (in the 2nd trimester-equivalent) on NMDA-induced seizures in developing rats at postnatal day 7 (P7, the equivalent of preterm newborns) and P15 (the equivalent of term infants). Pregnant Sprague-Dawley rats were given a single oral dose of ethanol (5 g/kg body weight) at E8 or E18 and the postpartum rats were tested for the susceptibility to NMDA-induced seizures at either P7 or P15. NMDA-induced seizures consisted of wild running-like behavior (WRLB), flexion seizures (FSs), clonic seizures (CSs), GTCSs, and tonic seizures (TSs); these seizures were observed in both control-treated and PAE-treated, male and female, P7 and P15 rats. Quantification reveals that the overall prevalence of CSs, GTCSs and TSs occurrence were significantly increased in the E18-PAE group compared to E8-PAE group, adjusting for sex and postnatal day. Furthermore, the overall prevalence of FSs and TSs occurrence was significantly increased in PAE-treated males compared to females, adjusting for embryonic stage and postnatal day. The overall prevalence of WRLB and FSs occurrence was also increased in PAE-P7 rats compared to PAE-P15 rats, adjusting for sex and embryonic stage. We conclude that the susceptibility to develop GTCSs was higher when PAE occurred in the 2nd rather than in the 1st trimester-equivalent of gestation.
Assuntos
Etanol/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Convulsões/induzido quimicamente , Animais , Feminino , Masculino , Gravidez , Ratos , Ratos Sprague-DawleyRESUMO
Voltage-gated calcium (Ca(2+)) channels are thought to play an important role in epileptogenesis and seizure generation. Here, using the whole cell configuration of patch-clamp techniques, we report on the modifications of biophysical and pharmacological properties of high threshold voltage-activated Ca(2+) channel currents in inferior colliculus (IC) neurons of the genetically epilepsy-prone rats (GEPR-3s). Ca(2+) channel currents were measured by depolarizing pulses from a holding potential of - 80 mV using barium (Ba(2+)) as the charge carrier. We found that the current density of high threshold voltage-activated Ca(2+) channels was significantly larger in IC neurons of seizure-naive GEPR-3s compared to control Sprague-Dawley rats, and that seizure episodes further enhanced the current density in the GEPR-3s. The increased current density was reflected by both a - 20 mV shifts in channel activation and a 25% increase in the non-inactivating fraction of channels in seizure-naive GEPR-3s. Such changes were reduced by seizure episodes in the GEPR-3s. Pharmacological analysis of the current density suggests that upregulation of L-, N- and R-type of Ca(2+) channels may contribute to IC neuronal hyperexcitability that leads to seizure susceptibility in the GEPR-3s.