Dieldrin induced kindling in the rat

Repetitive exposure of rats to dieldrin (5 mg/kg) on alternate days results in a progressive elevation in seizure severity. This effect is attributable to kindling and not to accumulation of dieldrin in the brain since seizure severity increased over the entire 19 day exposure period whereas dieldrin brain concentrations had peaked on or before the fourth administration and brain concentrations in rats given 10 or 15 mg/kg were higher on the first day of exposure than concentrations in rats administered 5 mg/kg at any time. In spite of this, seizure ranks were significantly higher during repetitive exposure to 5 mg/kg. The convulsive threshold concentration of dieldrin in brains of naive rats was 5.15 μg/g, a brain level never attained by rats given 5 mg/kg every other day. Nevertheless, the 5 mg/kg rats did develop severe convulsions and 4 of 10 died during repetitive administration. These data strongly implicate kindling as the basic cause for the progressive increase in seizure response upon repetitive exposure.