| Research Abstract |
The El mouse is an inbred mutant strain susceptible to convulsive seizures induced by tossed-up stimulation. Protein synthesis in vitro of the synaptosomal plasma membranes isolated from cerebral cortices of El(+) mice was compared with those of El(o) mice, which have not been stimulated and convulsed after virth, and seizure non-susceptible ddY or <C_57> BL mice as the controls. No significant difference was observed in protein synthesis of plasma membranes among four groups. The effects of potassium and sodium ions, and RNase, chloramphenicol, cycloheximide, puromycin, and ouabain did not significantly differ among four groups of mice. The protein synthesis of plasma membranes in El(+) mice was increased in pre- and post-ictal phases caused by tossed-up stimulation, except to tonic convulsive phase, implying that impairment of synapses in El(+) mice was restored by enhancement of protein synthesis. The pattern of plasma membrane protein analyzed by SDS-PAGE showed 5 major bands containing molecular weights of 15,000, 44,000, 54,000, 67,000 and 120,000, and 20 to 30 minor bands. The protein of 67,000 in El(+) mice during interictal phases was lower than those of El(o), <C_57> BL and ddY mice, while the protein of 120,000 in El(+) mice was decreased by seizures. The newly synthesized protein was detected to be 18,000, 62,000 and 80,000 by fluorography in four groups of mice, and that of 62,000 was decreased by seizures of El(+) mice. The proteins synthesized in polysomes were 54,000, 62,000, 78,000, 92,000, 104,000 and 125,000. These were same in four groups of mice and no remarkable difference was observed by seizures of El(+) mice. The above results suggest that proteins of 67,000 and 120,000 in plasma membranes of synaptosomes of El mouse cerebral cortices might be associated with seizure-susceptibility itself.
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