Proconvulsant actions of lindane: effects on afterdischarge thresholds and durations during amygdaloid kindling in...

Daily exposure to lindane, 5 mg/kg, produced a number of consistent changes in rats undergoing amygdaloid kindling. Lindane decreased the number of afterdischarge-evoking stimulations required to produce the fully kindled state, increased the length of each successive afterdischarge during kindling and increased the severity of each convulsive response during kindling. However, lindane exposure did not change the total seconds of afterdischarge activity required to create the fully kindled state. In this study the enhancement of kindling rates by lindane stemmed primarily from an increase in the duration of epileptiform activity following each amygdaloid stimulation. These proconvulsant effects cannot be attributed to a lowering of seizure thresholds by lindane. Thresholds evaluated at different times during and after completion of kindling were either unaffected or actually elevated by lindane exposure. The length and severity of seizures evoked in fully kindled subjects by amygdaloid stimulation were much less affected by lindane exposure. This indicates that the most useful period for demonstrating proconvulsant activity with the kindling seizure model is during the dynamic phase of seizure development. Once the process has reached completion, seizures are maximally expressed, and their duration is controlled by processes not as susceptible to lindane exposures.