N-methyl-D-aspartate receptor activation regulates refractoriness of status epilepticus to diazepam

Status epilepticus, prolonged intermittent or continuous seizure activity lasting 30 min or longer, is associated with high morbidity and mortality. The longer a seizure persists, the more refractory to treatment it becomes. The pilocarpine model of status epilepticus in rodents develops refractoriness to many first-line treatments as seizure duration increases, rendering it a good model to study refractory status epilepticus. This study was initiated to study the development of refractoriness of pilocarpine-induced status epilepticus to diazepam. Early pilocarpine-induced status epilepticus responded rapidly to diazepam treatment, whereas status epilepticus of longer duration became increasingly less responsive to treatment. Dizocilpine maleate-pretreated animals responded rapidly to diazepam treatment, even after 60 min of status epilepticus. Animals administered dizocilpine maleate at 15, 30 or 60 min after the onset of status epilepticus also demonstrated a rapid response to diazepam compared to pilocarpine-alone-treated animals. The longer the status epilepticus progressed prior to dizocilpine maleate injection, the longer the status epilepticus lasted after diazepam treatment. However, in all cases where dizocilpine maleate was administered, one injection of diazepam was able to terminate the status epilepticus, in contrast to the animals that did not receive dizocilpine maleate, in which the seizure was only attenuated. The results indicate that N-methyl-D-aspartate receptor activation plays a role in the seizure-induced refractoriness to benzodiazepines in status epilepticus, and blocking N-methyl-D-aspartate receptor activation converts refractory status epilepticus to a seizure responsive to benzodiazepine therapy. These findings offer insights into developing novel therapeutic interventions to improve the treatment of status epilepticus. Understanding the molecular mechanisms that mediate the effects of N-methyl-D-aspartate receptor activation on the development of resistance to treatment in status epilepticus will provide rational insights into more rapid methods to terminate seizure activity in this condition.