Evaluating anaesthetics for improving scientific research and welfare using larval zebrafish

Establishing anaesthesia for ensuring both animal welfare and compatibility with protocols required for different areas of scientific research is vital. Zebrafish (Danio rerio) are one of the most used animal models in research; however, little is known about the appropriateness of anaesthetic used for this species, especially for embryo-larval life stages. Using a combination of whole-brain functional imaging, quantification of cardiovascular performance, and behaviour, we explore the efficacy and tolerability of six widely used fish anaesthetics (2-phenoxyethanol, benzocaine, etomidate, MS222, isoeugenol and quinaldine sulfate) in larval zebrafish. We show that MS222 and quinaldine sulfate are the most suitable for achieving deep anaesthesia, while etomidate is better suited for studies focused on the cardiovascular system. Only quinaldine sulfate was found to be aversive. Our findings aid researchers for selecting the most suitable anaesthetic compounds and concentrations for their specific research goals, and the refinement of studies using anaesthesia in larval zebrafish.