High-throughput zebrafish intramuscular recording assay

•Multiple zebrafish intramuscular recording was possible using a microfluidic chip.•Intramuscular activities of zebrafish larvae were obtained while they stayed in water.•Feasibility of the developed system was demonstrated using three different chemicals. Despite tremendous efforts in utilizing zebrafish in neurological disease studies, owing to their easy handling, low cost, fast growth cycle, fecundity, high genetic similarity to humans, and transparency, the high-throughput electrophysiology methods for zebrafish are still absent. Although methods to detect intramuscular activities of adult and larval zebrafish have been previously introduced, the methods are complicated and time-consuming. Therefore, they have not been widely used in the zebrafish research community. We propose a high-throughput muscular activity measurement method using a simple and clever way of trapping zebrafish with microfluidic chip technology. Zebrafish larvae at 5 days post-fertilization were successfully retained in the designed microfluidic chip and were able to maintain their respiration for more than 24 h as long as the water was supplied through the inlet of the chip. The intramuscular activities of the larvae were obtained while they remained in the water. Significantly, this is the first reported method that can be used for measuring intramuscular activities while the larvae are inside the water. As a demonstration, we successfully modulated the locomotor activities of zebrafish using three different chemicals, proving that the developed method can be useful in monitoring intramuscular activities from multiple larvae and assessing the efficacy of pharmaceuticals.