Beneficial outcome of urethane treatment following status epilepticus in a rat organophosphorus toxicity model

• Authors: Asheebo Rojas, Emory University; Wenyi Wang, Emory University; Avery Glover, Emory University; Zahra Manji, Emory University; Yujiao Fu, Emory University; Raymond J Dingledine, Emory University
• Journal Title: eNeuro
• Volume: Volume 5, Number 2
• Publisher: Society for Neuroscience: eNeuro | 2018-03-01, Pages Eneuro.0070-18.2018-Eneuro.0070-18.2018
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1523/ENEURO.0070-18.2018
• Subjects: Health Sciences, Pharmacology; Health Sciences, General
• Keywords: DFP; EEG; diazepam; hippocampus; neurodegeneration; urethane

Abstract

The efficacy of benzodiazepines to terminate electrographic status epilepticus (SE) declines the longer a patient is in SE. Therefore, alternative methods for ensuring complete block of SE and refractory SE are necessary. We compared the ability of diazepam and a subanesthetic dose of urethane to terminate prolonged SE and mitigate subsequent pathologies. Adult Sprague Dawley rats were injected with diisopropylfluorophosphate (DFP) to induce SE. Rats were administered diazepam (10 mg/kg, ip) or urethane (0.8 g/kg, s.c.) 1 h after DFP-induced SE and compared to rats that experienced uninterrupted SE. Large-amplitude and high-frequency spikes induced by DFP administration were quenched for at least 46 h in rats administered urethane 1 h after SE onset as demonstrated by cortical electroencephalography (EEG). By contrast, diazepam interrupted SE but seizures with high power in the 20- to 70-Hz band returned 6-10 h later. Urethane was more effective than diazepam at reducing hippocampal neurodegeneration, brain inflammation, gliosis and weight loss as measured on day 4 after SE. Furthermore, rats administered urethane displayed a 73% reduction in the incidence of spontaneous recurrent seizures after four to eight weeks and a 90% reduction in frequency of seizures in epileptic rats. By contrast, behavioral changes in the light/dark box, open field and a novel object recognition task were not improved by urethane. These findings indicate that in typical rodent SE models, it is the return of SE overnight, and not the initially intense 1-2 h of SE experience, that is largely responsible for neurodegeneration, accompanying inflammation, and the subsequent development of epilepsy.