Neuropathology of seizures in the immature rabbit

Acute morphologic changes of brain due to chemically induced seizures are studied in developing rabbits. Accordingly, rabbits of postnatal days 6 and 7 (p6-7) and p10-12 are injected with a single dose of 1-6 mg/kg kainic acid (KA) intraperitoneally (i.p.) or injected with a single dose of 200-300 mg/kg pilocarpine subcutaneously (s.c.). Many animals developed seizures of varying severity and length. Histologic examination of brain 2 days following injection showed that KA-induced seizures did not cause neuronal death. Pilocarpine-induced seizures resulted in neuronal death mainly involving the CA1 region of hippocampus. In the p6-7 group, only a small number of brains were involved, lesions were mild and limited to CA1. In the p10-12 group, majority of the brains were damaged, lesions were relatively severe, and in some brains extended beyond the CA1 region involving the subiculum, CA3, cortex, and amygdala. Measurements of physiologic parameters indicate that these changes were not secondary to hypoxemia during seizures. However, there was hypotension and hyperthermia, both of which may contribute to brain damage during seizures. The findings suggest that pilocarpine-induced seizures during the second postnatal week in rabbits is a useful model to study the morphologic changes of brain due to seizure in the developing animal and also to assess the systemic physiologic alterations during seizures.