Eight Flurothyl-Induced Generalized Seizures Lead to the Rapid Evolution of Spontaneous Seizures in Mice: A Model of Epileptogenesis with Seizure Remission.

UNLABELLED: The occurrence of recurrent, unprovoked seizures is the hallmark of human epilepsy. Currently, only two-thirds of this patient population has adequate seizure control. New epilepsy models provide the potential for not only understanding the development of spontaneous seizures, but also for testing new strategies to treat this disorder. Here, we characterize a primary generalized seizure model of epilepsy following repeated exposure to the GABAA receptor antagonist, flurothyl, in which mice develop spontaneous seizures that remit within 1 month. In this model, we expose C57BL/6J mice to flurothyl until they experience a generalized seizure. Each of these generalized seizures typically lasts <30 s. We induce one seizure per day for 8 d followed by 24 h video-electroencephalographic recordings. Within 1 d following the last of eight flurothyl-induced seizures, ∼50% of mice have spontaneous seizures. Ninety-five percent of mice tested have seizures within the first week of the recording period. Of the spontaneous seizures recorded, the majority are generalized clonic seizures, with the remaining 7-12% comprising generalized clonic seizures that transition into brainstem seizures. Over the course of an 8 week recording period, spontaneous seizure episodes remit after ∼4 weeks. Overall, the repeated flurothyl paradigm is a model of epileptogenesis with spontaneous seizures that remit. This model provides an additional tool in our armamentarium for understanding the mechanisms underlying epileptogenesis and may provide insights into why spontaneous seizures remit without anticonvulsant treatment. Elucidating these processes could lead to the development of new epilepsy therapeutics. SIGNIFICANCE STATEMENT: Epilepsy is a chronic disorder characterized by the occurrence of recurrent, unprovoked seizures in which the individual seizure-ictal events are self-limiting. Remission of recurrent, unprovoked seizures can be achieved in two-thirds of cases by treatment with anticonvulsant medication, surgical resection, and/or nerve/brain electrode stimulation. However, there are examples in humans of epilepsy with recurrent, unprovoked seizures remitting without any intervention. While elucidating how recurrent, unprovoked seizures develop is critical for understanding epileptogenesis, an understanding of how and why recurrent, unprovoked seizures remit may further our understanding and treatment of epilepsy. Here, we describe a new model of recurrent, unprovoked spontaneous seizures in which the occurrence of spontaneous seizures naturally remits over time without any therapeutic intervention.

Multidimensional Genetic Analysis of Repeated Seizures in the Hybrid Mouse Diversity Panel Reveals a Novel Epileptogenesis Susceptibility Locus.

Epilepsy has many causes and comorbidities affecting as many as 4% of people in their lifetime. Both idiopathic and symptomatic epilepsies are highly heritable, but genetic factors are difficult to characterize among humans due to complex disease etiologies. Rodent genetic studies have been critical to the discovery of seizure susceptibility loci, including Kcnj10 mutations identified in both mouse and human cohorts. However, genetic analyses of epilepsy phenotypes in mice to date have been carried out as acute studies in seizure-naive animals or in Mendelian models of epilepsy, while humans with epilepsy have a history of recurrent seizures that also modify brain physiology. We have applied a repeated seizure model to a genetic reference population, following seizure susceptibility over a 36-d period. Initial differences in generalized seizure threshold among the Hybrid Mouse Diversity Panel (HMDP) were associated with a well-characterized seizure susceptibility locus found in mice: Seizure susceptibility 1 Remarkably, Szs1 influence diminished as subsequent induced seizures had diminishing latencies in certain HMDP strains. Administration of eight seizures, followed by an incubation period and an induced retest seizure, revealed novel associations within the calmodulin-binding transcription activator 1, Camta1 Using systems genetics, we have identified four candidate genes that are differentially expressed between seizure-sensitive and -resistant strains close to our novel Epileptogenesis susceptibility factor 1 (Esf1) locus that may act individually or as a coordinated response to the neuronal stress of seizures.