Effects of oxygen insufflation during pilocarpine-induced status epilepticus on mortality, tissue damage and seizures

• O2 treatment during pilocarpine-induced status epilepticus (SE) reduces acute mortality.
• Mossy fiber sprouting, cell loss or Hsp27 expression is not altered by O2 treatment during SE.
• O2 treatment during SE might delay onset of chronic epilepsy, but cannot prevent seizure occurrence.

SummaryPurposeThis prospective, randomized study was performed to investigate the effects of oxygen (O2) treatment during sustained epileptic activity on mortality, subsequent seizure frequency, and neuronal damage.MethodsStatus epilepticus (SE) was induced by intraperitoneal injection of 340 mg/kg pilocarpine, and terminated by diazepam after 40 min. During SE, rats were randomized to O2 treatment (insufflation rate of 1.5 l/min O2) during SE or normal air conditions. Outcome measures were SE-related mortality, seizure occurrence, mossy fiber sprouting, neuronal cell loss and expression of 27-kDa heat-shock protein (Hsp27).ResultsO2-treated and O2-untreated animals did not differ with respect to SE latency, diazepam dose required to stop SE. While 7/38 rats died during SE in the O2-untreated group, very little mortality (1/38) occurred in the O2-treated group (P < 0.05). However, within 1 h after SE termination, seven O2-treated rats died which was not observed in the O2-untreated group indicating no significant difference in overall mortality. There was a tendency towards lower seizure rate in the O2-treated group at one month after pilocarpine-induced SE. Three months after SE, however, seizure rates were no longer different between both groups. Moreover, mossy fiber sprouting, neuronal cell loss and Hsp27 expression did not differ between O2-treated and O2-untreated groups.ConclusionOur findings indicate that O2 treatment might delay the relative risk of epileptic seizures following an initial brain injury, but it may also lead to a rather unfavorably increased heterogeneity of epileptogenesis in experimental studies.