Absence epilepsy in male and female WAG/Rij rats: A longitudinal EEG analysis of seizure expression.

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.

Screening of GABRB3 in French-Canadian families with idiopathic generalized epilepsy.

Mutations in the GABRB3 have been recently associated with childhood absence epilepsy (CAE) in families from Honduras and Mexico. In this study, we aimed to determine the frequency of mutation in this gene in our cohort of families with CAE and other related idiopathic generalized epilepsy (IGE) syndromes. We screened the open reading frame of GABRB3 in 183 French-Canadian individuals with IGE, including 88 with CAE. A total of nine single nucleotide polymorphisms (SNPs) have been identified,five of which are novel. The previously described P11S missense mutation was found in three affected and one unaffected individuals from a French-Canadian family. However, the P11S variant was also found in one of our 190 control individuals of French-Canadian origin, suggesting that this variant is rather a rare polymorphism in this population. Further screening of other IGE cohorts from various ethnic origins would help to confirm the association between this rare functional variant and epilepsy.

[The myelin mutant taiep as a model for abscence crisis]. / El mutante de mielina taiep como un modelo de crisis de ausencia.

BACKGROUND: Taiep rat is a myelin mutant rat with hypomyelination followed by progressive demyelination. This mutant presents cortical discharges with a spindle form, with an ascending and descending phases similar to absence epilepsy. METHODS: Taiep rats were maintained under standard animal room conditions with free access to balanced rodent pellets and tap water. Rats were anesthetized with chloral hydrate under aseptic conditions; three stainless steel screws and a bipolar electrode were implanted in the hippocampus. The signals were amplified, filtered and recorded using a video-EEG Harmonie system (Canada). All data were analyzed using Sensa and Luna modules. RESULTS: Our results showed that taiep rats have spike-wave discharges (SWD) during wake, slow wake sleep (SWS) and rapid eye movement (REM), being statistically higher and longer during awake period than SWS or REM sleep. The systemic administration of pilocarpine, a cholinergic agonist, increased dramatically the cortical discharges with five characteristic seizures patterns and concomitantly decreased the frequency and duration of absence crisis. However, only 80% of the taiep rats tested showed this paroxysm. On the other hand, 100% of control Sprague-Dawley rats showed tonic clonic seizures, indicating some type of resistance to this muscarinic cholinergic drug in taiep rats. CONCLUSIONS: These results showed that the taiep rat, a myelin mutant, is a good model for the electrophysiological and pharmacological study of absence epilepsy, particularly considering its resistance to pilocarpine-induced seizures.