Nerve agents are amongst the deadliest chemicals known to man and continue to pose a significant societal threat. Nerve agents function via inhibition of acetylcholinesterase and cause seizures, which can progress to protracted, recurring seizures. Recurrent seizures can cause irreparable damage to the brain through extensive neuronal cell death. The first line treatment for nerve agent exposure includes benzodiazepines; however, these are sometimes ineffective. The greater the delay between exposure and treatment, for example on the battlefield, the lower the likelihood of treatment effectiveness. Consequently, alternative treatment options are required. Current methods used for testing new treatments are reliant on the use of rodents and the procedures are invasive, costly and time consuming. As such, more ethically and economically favourable methods for the testing of such treatments are needed. We propose using non-protected larval zebrafish as a non-mammalian replacement model. Non-protected larval zebrafish have already been shown to be responsive to a range of seizure-inducing pharmacologies, and are amenable to non-invasive higher throughput testing strategies. Our overall aim is to build on techniques developed during previous NC3Rs-funded research at Portsmouth and Exeter Universities to provide the defence research community with a non-protected larval zebrafish model that can be used to identify novel therapeutics to treat nerve agent-induced seizures. We will modify a technique in which seizures are visualised using light sheet microscopic Ca2+ imaging in a 4dpf transgenic zebrafish, to allow single z-plane assessment of neural activity on a standard confocal microscope. We will then refine behavioural models of seizure activity to create high throughput assays for the accurate quantification of convulsive behaviour. The new technology will be transferred to Dstl, where the direct relevance for the study of nerve agents will be definitively assessed.
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