• Xiaoxuan Yang, Youssef Jounaidi, Jennifer B Dai, Francisco Marte-Oquendo, Elizabeth S Halpin, Lauren E Brown, Richard Trilles, Wenqing Xu, Renee Daigle, Buwei Yu, Scott E Schaus, John A Porco, and Stuart A Forman.
• From the Department of Anesthesiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China (X.Y., B.Y.) the Department of Anesthesia, Critical Care and Pain Medicine (X.Y., Y.J., J.B.D., F.M.-O., E.S.H., S.A.F.) the Center for Regenerative Medicine (R.D.) Massachusetts General Hospital, Boston, Massachusetts; and the Department of Chemistry and Center for Molecular Discovery, Boston University, Boston, Massachusetts (L.E.B., R.T., W.X., S.E.S., J.A.P.).
• Anesthesiology. 2018 Sep 1; 129 (3): 459-476.

What We Already Know About This TopicWHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Many general anesthetics were discovered empirically, but primary screens to find new sedative-hypnotics in drug libraries have not used animals, limiting the types of drugs discovered. The authors hypothesized that a sedative-hypnotic screening approach using zebrafish larvae responses to sensory stimuli would perform comparably to standard assays, and efficiently identify new active compounds.MethodsThe authors developed a binary outcome photomotor response assay for zebrafish larvae using a computerized system that tracked individual motions of up to 96 animals simultaneously. The assay was validated against tadpole loss of righting reflexes, using sedative-hypnotics of widely varying potencies that affect various molecular targets. A total of 374 representative compounds from a larger library were screened in zebrafish larvae for hypnotic activity at 10 µM. Molecular mechanisms of hits were explored in anesthetic-sensitive ion channels using electrophysiology, or in zebrafish using a specific reversal agent.ResultsZebrafish larvae assays required far less drug, time, and effort than tadpoles. In validation experiments, zebrafish and tadpole screening for hypnotic activity agreed 100% (n = 11; P = 0.002), and potencies were very similar (Pearson correlation, r > 0.999). Two reversible and potent sedative-hypnotics were discovered in the library subset. CMLD003237 (EC50, ~11 µM) weakly modulated γ-aminobutyric acid type A receptors and inhibited neuronal nicotinic receptors. CMLD006025 (EC50, ~13 µM) inhibited both N-methyl-D-aspartate and neuronal nicotinic receptors.ConclusionsPhotomotor response assays in zebrafish larvae are a mechanism-independent platform for high-throughput screening to identify novel sedative-hypnotics. The variety of chemotypes producing hypnosis is likely much larger than currently known.

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