Damage induced by systemic kainic acid in rats is dependent upon seizure activity--a behavioral and morphological study.

Kainic acid (KA) was injected intraperitoneally into rats at a dose (9 mg/kg) which produced status epilepticus in approximately 50% of the animals. Rats were categorized into groups that displayed status epilepticus, partial seizures or no effect in the 4 hr following kainic acid injection. Behavioral and morphological changes were characterized for each group. Rats that were not affected by kainic acid were indistinguishable from a saline-injected control group. When sacrificed 4 hr after treatment, rats displaying partial seizures showed morphological changes similar to, but less severe than, those exhibiting status epilepticus. Additional groups were tested and sacrificed 7 days (d) after treatment. Rats from the limited seizure group showed little behavioral or morphological response, while animals from the status epilepticus group had marked behavioral deficits and severe lesions. The tissue damage and its distribution were similar to lesions observed after seizures induced by other convulsants, and in spontaneously epileptic dogs. These results suggest that the extent of damage resulting from systemic administration of KA is dependent on the extent of seizure activity, which may in turn be related to the influence of kainic acid and other excitatory amino acids on the limbic system.