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Encyclopedia of Experiments: Biology

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Escape Response Assay


Escape Response Assay: A Method to Study the Response of Zebrafish Larva to Touch Stimuli



- To begin, gently transfer a few embryos into a Petri dish containing embryo medium. Now hold the chorion with forceps and make a tear in it with another forceps.

Next, gently push the embryo through the tear. Removing the chorion from the embryo accelerates its growth and movement. To get rid of the debris, transfer the embryos to another Petri dish containing embryo medium using a Pasteur pipette.

Place the Petri dish in an incubator, and let the embryos grow at 28 degrees Celsius. Set an illuminated water filled microscope stage to 28 degrees Celsius prior to the experiment to avoid any temperature related deviations in larval behavior.

Place the Petri dish on the stage and mount in the camera above the dish. Next, center the embryo in the camera's field of view. Now gently touch the embryo with a blunt needle, and record the larval response on the video camera recording software.

Upon stimulus, the embryo exhibits a powerful escape response-- a burst swim along with sharp turns. Measure the time between the touch and the larvae's peak acceleration during its escape.

In the example protocol, we will observe the response of zebrafish larvae to external stimuli.

- To perform the assay, place a Petri dish filled with approximately 25 milliliters of embryo medium onto an illuminated temperature controlled stage set to approximately 28 degrees Celsius. Mount the high speed camera above the dish. Launch the video recording software, and set the capture speed to 1,000 frames per second to ensure fast swimming speeds can be captured.

Position the embryo in the center of the Petri dish, clearly visible in the field of view. Press record and then deliver a mechanosensory stimulus by gently touching the embryo with a blunt needle on top of the head.

Stop the recording once the embryo has swum out of the field of view or returned to rest.

- Repeated testing of the same larvae may lead to habituation or promote muscle weakness in some disease models, resulting in reduced response to the tactile stimulus. Therefore, each embryo should only be tested once.

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