Mechanism of epileptogenesis of the Mongolian gerbil, an animal model of epilepsy.

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The Mongolian gerbil (Meriones unguiculatus) is a genetical animal model of epilepsy. Using a seizure-sensitive strain we had established previously, we found that the rhythmical backward movement of the pinnae occurring after posture change, a strong inducer of the seizure, was the early phase of the epiletogenesis and that the vestibular cortex which brings the backward movement of the pinnae by electrical stimulation. A telemeter machine showed that the repetitive injection of pentylentetrazole and other events which induce the seizure-related behaviors induced a sharp wave at this area accompanied with similar ear movement, which may suggest that this area participates in the early phase of epileptogenesis. How the motor cortex works is now under investigation. The animals of a seizure-resistant strain established by Dr. Murashima (Tokyo Institute of Psychiatry) did not show the ear movement after posture change but their facial nerve was found to enter into the ear muscles similarly to the sensitive strain, which suggests other component(s) in the pathway between the vestibular end-origan and the ear muscle is responsible for the difference observed. A protein like P70, a 70kDa protein considered to be involved in the epileptogenesis of cobalt-treated rat, was analyzed and found that it changed its location to the plasma membrane of the neurons where it often colocalized with the intrinsic fluorescent materials in the cerebral cortex during the term of the epileptogenesis. This protein seems to resemble albumin of which amino acid sequence was determined from cDNA in this study. Albumin mRNA was found in the brain of the 3-month-old gerbils. Thus, modified albumin may participate to change the properties of ion channels at the cell periphery like P70.