The Wakayama Epileptic Rat(WER), a New Mutant Exhibiting Tonic-clonic Seizures and Absence-like Seizures.

Abstract

Abstract:A new mutant, the Wakayama epileptic rat (WER), exhibiting both spontaneous absence-like behavior and tonic-clonic convulsions, was identified in a colony of Wistar rats. To determine clear seizure characteristics of this mutant strain, we analyzed the mode of inheritance of the convulsion and observed patterns of electroencephalogram (EEG) during the seizures. F 1 progeny were produced between the founder male and normal females of the same colony. Animals were monitored through the inbreeding course to analyze genetic control of epileptic behavior. EEGs were recorded using affected animals in the F 3-4 and post F 13 generations. After the F 2 generation, affected rats spontaneously exhibited both absence-like immobile behavior and tonic-clonic convulsions. The absence-like seizures were characterized by motor arrest and head droop. The tonic-clonic convulsions began with neck and forelimb clonus, wild jumping/running, and opisthotonic posturing, and evolved to tonic, then clonic convulsions. Most convulsion onsets occurred between 25-70 days of age. Mating experiments revealed that 0%(0/18) of the animals in F 1 , 10%(3/26) in F 2 , 17%(1/6) in backcross progeny and 86% (100/116) in progeny of crosses between epileptic rats showed tonic-clonic convulsions. Ictal cortical EEGs were characterized by 4-6 (5.1 ± 0.4, mean ± SD) Hz spike-and-wave complexes in the absence-like seizures and by low-voltage fast waves in the tonic-clonic convulsions. This new mutant rat spontaneously exhibited both absence-like and tonic-clonic seizures. The tonic-clonic seizure was inherited as an autosomal recessive trait with 86% incidence. Thus, the new mutant rat may become a useful model for studying human inherited epilepsies.

Two Types of Seizures in Homocysteine Thiolactone-Treated Adult Rats, Behavioral and Electroencephalographic Study

“…Absence-like seizures concomitantly exist with tonic convulsions in spontaneous epileptic rat (SER) (Serikawa et al 1991), Wakayama epileptic rats (WER) (Tsubota et al 2003), or tremor rats (Kitada et al 2000). All of them show paroxysmal, synchronized 5-7 Hz spike-wave complexes in cortical EEG during the absence-like state characterized by immobility and staring.…”

Advances on genetic rat models of epilepsy

“…After the F 2 generation, affected rats spontaneously exhibited both absence-like immobile behavior with SWD in cortical EEG and GTCS. The GTCS in WER strain established was confirmed to be inherited as an autosomal recessive trait with 86% incidence [ 112 ].…”