Hexahydro-1,3,5-trinitro-1,3,5-triazine, or Royal Demolition Explosive (RDX), is a major component of plastic explosives such as C-4. Acute exposures from intentional or accidental ingestion are a documented clinical concern, especially among young male U.S. service members in the armed forces. When ingested in large enough quantity, RDX causes tonic–clonic seizures. Previous in silico and in vitro experiments predict that RDX causes seizures by inhibiting α1β2γ2 γ-aminobutyric acid type A (GABAA) receptor-mediated chloride currents. To determine whether this mechanism translates in vivo, we established a larval zebrafish model of RDX-induced seizures. After a 3 h of exposure to 300 µM RDX, larval zebrafish exhibited a significant increase in motility in comparison to vehicle controls. Researchers blinded to experimental group manually scored a 20-min segment of video starting at 3.5 h post-exposure and found significant seizure behavior that correlated with automated seizure scores. Midazolam (MDZ), an nonselective GABAAR positive allosteric modulator (PAM), and a combination of Zolpidem (α1 selective PAM) and compound 2-261 (β2/3-selective PAM) were effective in mitigating RDX-triggered behavioral and electrographic seizures. These findings confirm that RDX induces seizure activity via inhibition of the α1β2γ2 GABAAR and support the use of GABAAR-targeted anti-seizure drugs for the treatment of RDX-induced seizures.

Diisopropylfluorophosphate (DFP) is an organophosphate (OP) that is commonly used to study the neurotoxic effects of acutely intoxicating OP exposure. In preliminary studies, we discovered abnormal deaths in DMSO-only exposed larvae housed in the same plate as DFP-exposed larvae, and hypothesized that DFP volatilizes and cross-contaminates wells when using a 96-well plate exposure method for exposing zebrafish larvae. Survivability and acetylcholinesterase activity assays confirmed DFP presence in the tissues of zebrafish ostensibly exposed to DMSO only. These findings indicate DFP cross-contamination, which raises concerns for the experimental design of studies evaluating the toxicity of volatile and semi-volatile substances.

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