Multi-phenotypic and bi-directional behavioral screening of zebrafish larvae.

Multi-phenotypic screening of zebrafish larvae, such as monitoring the heart and tail activities, is important in biological assays. Microfluidic devices have been developed for zebrafish phenotypic assays, but simultaneous lateral-dorsal screening of the same larva in a single chip is yet to be achieved. We present a multi-phenotypic microfluidic device for monitoring of tail movement and heart rate (HR) of 5-7-day postfertilization zebrafish larvae. Tail movements were stimulated using electric current and quantified in terms of response duration (RD) and tail beat frequency (TBF). The positioning of a right-angle prism provided a lateral view of the larvae and enabled HR monitoring. Investigations were performed on zebrafish larvae exposed to 3% ethanol, 250 μM 6-hydroxydopamine (6-OHDA) or 1 mM levodopa. Larvae exposed to ethanol showed a significant drop in HR, whereas electric stimulation increased the HR temporarily. Larvae experienced a significant drop in RD, TBF and HR when exposed to 6-OHDA. HR was not affected by levodopa post-treatment, whereas RD and TBF were restored to normal levels. The results showed potential for applications that involve monitoring of cardiac and behavioral parameters in zebrafish larvae. Tests can be done using the same chip, without changing the larvae's orientation. This eliminates undue stress caused by reorientation, which may affect their behavior, and the use of separate devices to obtain dorsal and lateral views. The device can be implemented to improve multi-phenotypic and quantitative screening of zebrafish larvae in response to chemical and physical stimuli in different zebrafish disease models.