Abstracts

Rationale: Exposure to organophosphates (OP), or organophosphate nerve agents, results in status epilepticus (SE) and neuronal damage in the central nervous system. SE can be lethal; however, early control of seizure activity minimizes mortality, as well as neuronal damage. Unfortunately, in the event of a mass release in a civilian setting or on the battlefield, treatment of casualties is likely to be delayed to periods longer than typically acceptable for current medications that can be administered without hospital support.  Therefore, there is a pressing need for anti-seizure treatments that can be administered with a significant delay and in a pre-hospital setting.  Now in our second year, the CounterACT Neurotherapeutic Screening (CNS) Program has screened 9 externally submitted and 8 internally submitted test compounds. Methods: For screening, male Sprague Dawley rats (150-200 g) were implanted with electrodes for recording of the electroencephalogram (EEG).  On treatment day, SE was induced by administration of diisopropyl fluorophosphate (DFP).  One hour after the start of SE, rats were co-administered midazolam (MDZ) and test compound.  EEG was recorded for 24 h at which time the rats were perfused, brains were sectioned and labeled with Fluoro-Jade B. Neuropathology was assessed as the number of Fluoro-Jade B positive neurons in 10 regions: dorsal CA1, dorsal CA3, hilus, ventral CA1, ventral CA3, amygdala, thalamus, and the parietal, entorhinal and piriform cortices.   Results: Of the coded, externally submitted compounds, we have seen significant anti-seizure effects in the presence and absence of MDZ for two compounds.  These compounds reduced both seizure power and seizure duration.  Each of these also reduced neuronal death in the presence of MDZ.  Tested in the absence of MDZ, both compounds were less effective in reducing seizures and cell death than MDZ.  These data can be compared to ganaxolone which had a minimal additional effect, or with bumetanide which had no additional effect, on seizures when either compound was co-administered with MDZ. Conclusions: These data demonstrate that OP-induced SE can be reversed by MDZ even when treated at a long-delay. Additionally, the effect of MDZ can be enhanced by add-on therapies and this combined treatment can significantly reduce neuronal death.   Funding: This research was supported by the NIH Office of the Director through an Inter-Agency Agreement (Y1-O6-9613-01) between the National Institute of Allergy and Infectious Diseases (NIAID) and DoD USAMRICD (A120-B.P2009-2) and under subcontract W81XWH-14-C-0119 to the University of Utah.