Abstracts

No animal model is widely accepted to study post stroke epilepsy. Photothrombotic brain infarction in Sprague-Dawley (SD) rats leads to the development of focal epileptic seizures ipsilateral to the cortical infarct in 50 % of the animals (Kharlamov et al, Epilepsy Research 2003; 56:185-203). In order to investigate the susceptibility to a proconvulsant agent, we tested the sensitivity of the animals to low doses of pentylenetetrazole (PTZ) in this model. Photothrombosis was performed on 8 male SD rats. Rose bengal (30 mg/kg) was injected intravenously. Photoactivation was performed with a 6 mm diameter cold white light focused over the left fronto-parietal cortex during 20 minutes. Six epidural screw electrodes were placed over the skull. EEG was recorded during 6 months. Eight male SD control rats were also recorded.Intraperitoneal (ip) PTZ, at 20 and 30 mg/kg, was injected 9 months and 11 months after surgery. The seizures were classified clinically: stage 1: staring; stage 2: diffuse myoclonus; stage 3: rearing on the hind legs; stage 4: full-blown generalized clonic convulsion and falling down. Among the 8 rats in which photothrombosis was induced, one died during status epilepticus 19 days after surgery. Two control rats died during the chronic EEG recording period. No spontaneous focal seizures were seen.
After ip PTZ 20 mg/kg, all control animals presented stage 1 seizures. Among rats with photothrombosis, one showed stage 3 and one showed stage 4 seizure.After ip PTZ 30 mg/kg, one control animal presented stage 1 seizures and 5 animal stage 4 seizures. Among rats with photothrombosis, one had stage 1 seizure, 2 had stage 2 seizures, one had stage 3 and 3 had stage 4 seizures. This study showed that after photothrombotic brain infarction, no animals had spontaneous focal seizures. After ip PTZ 20 mg/kg, there was a tendency for more severe seizures in animals with photothrombosis, compared to controls. This tendency is not confirmed after ip PTZ 30 mg/kg. Further experiments are ongoing to confirm the results of this pilot study, by increasing the number of animals and by testing other proconvulsant agents. (Supported by Fondation Erasme, ULB-H[ocirc]pital Erasme ; Clinical Epilepsy Grant, University Hospital, Gent.)