Neurosteroid and benzodiazepine combination therapy reduces status epilepticus and long‐term effects of whole‐body sarin exposure in rats

Abstract

Objective Our objective was to evaluate the protective efficacy of the neurosteroid pregnanolone (3α‐hydroxy‐5β pregnan‐20‐one), a GABA A receptor‐positive allosteric modulator, as an adjunct to benzodiazepine therapy against the chemical warfare nerve agent (CWNA) sarin (GB), using whole‐body exposure, an operationally relevant route of exposure to volatile GB. Methods Rats implanted with telemetry transmitters for the continuous measurement of cortical electroencephalographic (EEG) activity were exposed for 60 minutes to 3.0 LCt 50 of GB via whole‐body exposure. At the onset of toxic signs, rats were administered an intramuscular injection of atropine sulfate (2 mg/kg) and the oxime HI‐6 (93.6 mg/kg) to increase survival rate and, 30 minutes after seizure onset, treated subcutaneously with diazepam (10 mg/kg) and intravenously with pregnanolone (4 mg/kg) or vehicle. Animals were evaluated for GB‐induced status epilepticus (SE), spontaneous recurrent seizures (SRS), impairment in spatial memory acquisition, and brain pathology, and treatment groups were compared. Results Delayed dual therapy with pregnanolone and diazepam reduced time in SE in GB‐exposed rats compared to those treated with delayed diazepam monotherapy. The combination therapy of pregnanolone with diazepam also prevented impairment in the Morris water maze and reduced the neuronal loss and neuronal degeneration, evaluated at one and three months after exposure. Significance Neurosteroid administration as an adjunct to benzodiazepine therapy offers an effective means to treat benzodiazepine‐refractory SE, such as occurs following delayed treatment of GB exposure. This study is the first to present data on the efficacy of delayed pregnanolone and diazepam dual therapy in reducing seizure activity, performance deficits and brain pathology following an operationally relevant route of exposure to GB and supports the use of a neurosteroid as an adjunct to standard anticonvulsant therapy for the treatment of CWNA‐induced SE.

Delayed midazolam dose effects against soman in male and female plasma carboxylesterase knockout mice

“…Neurosteroids, such as allopregnanolone, are modulators of the major inhibitory GABAA receptor (reviewed in Ref. 42 ), as well as anticonvulsive properties, 43,44 and these effects may contribute to the increased protection against GD lethality that we observed in the female Es1 −/− mice in estrus. Further research on species differences in the impact of sex on the toxic outcome of CWNA exposure may be warranted.…”

Characterization of organophosphate‐induced brain injuries in a convulsive mouse model of diisopropylfluorophosphate exposure

“…Regardless of the OP triggering seizures, prolonged SE induced by DFP, soman, or sarin has been associated with important neuronal loss in the hippocampus and other brain regions. 4,15,16 Elevated delta activity has been suggested to predict neuronal damage in a soman-induced poisoning model. 17 In our study, power spectra analysis of animals experiencing SE showed us that, as opposed to all other studied frequencies that were elevated during SE, only delta frequencies remained increased in the 24-hour recording period.…”

Novel Genetically Modified Mouse Model to Assess Soman-Induced Toxicity and Medical Countermeasure Efficacy: Human Acetylcholinesterase Knock-in Serum Carboxylesterase Knockout Mice

“…Even when seizures seem to stop by the administration of diazepam at 1 or 2 h after GD exposure, the intermittent return of seizures is observed in rats so that the overall duration of seizures in the first 24 h after the toxic insult is similar to that of animals that did not receive any anti-seizure treatment [ 23 ]. Midazolam, recently approved for the treatment of acute repetitive seizures, increases survival in GD-exposed rats and Es1-/- mice but does not prevent the development of spontaneous recurrent seizures (SRS) or brain pathology when treatment is delayed [ 13 , 18 , 24 , 25 , 26 ].…”