Co-administration of subtherapeutic diazepam enhances neuroprotective effect of COX-2 inhibitor, NS-398, after lithium pilocarpine-induced status epilepticus

Abstract

RationaleSeizures during status epilepticus (SE) cause neuronal death and induce cyclooxygenase-2 (COX-2). Pilocarpine-induced SE was used to determine if COX-2 inhibition with NS-398, when administered alone or with diazepam, decreases the duration and/or intensity of SE and/or reduces neuronal injury in the rat hippocampus. MethodsElectroencephalogram (EEG) electrodes were implanted in male Sprague–Dawley rats. SE was induced with lithium-pilocarpine, and continuous EEG and video monitoring were performed for 24h. Rats were divided into four groups (n=8–14 rats/group) and received NS-398, diazepam, NS-398 and diazepam, or vehicle 30min after the first motor seizure. Six hours later, NS-398 injection was repeated in the NS-398 and in the NS-398+diazepam groups. The duration of SE (continuous spiking) and the EEG power in the γ-band were analyzed. FluoroJade B staining in the dorsal hippocampus at 24h after SE was analyzed semi-quantitatively in the CA1, CA3 and hilus. ResultsThe duration and intensity of electrographic SE was not significantly different across the four groups. In rats treated with NS-398 alone, compared to vehicle-treated rats, neuronal damage was significantly lower compared to vehicle-treated rats in the CA3 (27%) and hilus (27%), but neuroprotection was not detected in the CA1. When NS-398 was administered with diazepam, decreased neuronal damage was further obtained in all areas investigated (CA1: 61%, CA3: 63%, hilus: 60%). ConclusionsNS-398, when administered 30min after the onset of SE with a repeat dose at 6h, decreased neuronal damage in the hippocampus. Administration of diazepam with NS-398 potentiates the neuroprotective effect of the COX-2 inhibitor. These neuroprotective effects occurred with no detectable effect on electrographic SE.