Abstracts

Rationale: Status epilepticus (SE) leads to significant mortality and morbidity, and thus new neuroprotective strategies are needed. Diazepam belongs to the first line of therapeutic strategies in SE and is neuroprotective when administered at high doses within 2 h after induction of SE. Cyclooxygenase-2 (COX-2) is an inflammatory enzyme that is induced by epileptic seizures and is associated with neuronal death. The rat model of pilocarpine-induced SE was used to determine if a low dose of diazepam and COX-2 inhibitor (NS-398), when administered together, would decrease the severity of SE and reduce neuronal injury. Methods: Electroencephalogram (EEG) electrodes were implanted in 25 male Sprague-Dawley rats. SE was induced with lithium-pilocarpine, and continuous EEG and video monitoring were performed for 24 h. Diazepam (10 mg/kg, n = 8), diazepam and NS-398 (10 mg/kg, n = 8), or vehicle (0.5% methylcellulose, n = 9) were injected at 30 min after the first motor seizure. Diazepam and control groups received vehicle 6 h later, while the diazepam NS-398 group received NS-398. The severity of SE, evaluated as EEG power in the ?-band, was analyzed using an automated algorithm. FluoroJade B staining in the dorsal hippocampus at 24 h after SE was analyzed semi-quantitatively in CA1, CA3 and hilus of the dentate gyrus. Results: Analysis of the electrographic data showed no difference between the control, diazepam and diazepam NS-398 groups; severity of electrographic SE in the ?-band was similar in the three groups. Diazepam, at 10 mg/kg, did not have significant neuroprotective effect when injected at 30 min from first motor seizure. In rats treated with diazepam NS-398, compared to vehicle rats, neuroprotection was significant in CA1 (61 3%), CA3 (63 6%) and hilus of the dentate gyrus (60 12%), ANOVA followed by Dunnet s test, p<0.05. Compared to diazepam alone, the combination of diazepam and NS-398 led to significant neuroprotection in CA3 (57 5%) and hilus of the dentate gyrus (55 10%), p<0.05. Conclusions: We previously reported that the COX-2 inhibitor, when administered alone, decreased neuronal damage in the hippocampus (CA3: 27 4% and hilus of the dentate gyrus: 27 3%) without a detectable effect on the seizure activity associated with SE. The present data suggest that the combination of low-dose diazepam (10 mg/kg) with NS-398 leads to more effective neuroprotection in the hippocampus than NS-398 alone, and this occurs without an effect on the electrical activity during SE.