Zebrafish larvae display a robust startle response. Because this is mediated by neural pathways in a way similar to the process in higher vertebrates, startle response testing can be applied to a wide range of neuro-scientific studies.
The startle response can be evoked in different ways, such as via a light stimulus or a vibration stimulus. The former is standard in the DanioVision chamber.
To add a vibration stimulus, a small instrument called the Tapping Device can be inserted at the bottom of the basin where your well plate or petri dish is placed in the DanioVision Observation Chamber. (In the photo above, the cover plate is removed so you can see the built-in stimulus. In a functioning Observation Chamber, this part is covered.)
Vibration stimuli at different levels
Taps from this device cause vibrations in the water, evoking a startle response in your animals. You can set the stimulus intensity at different forces – there are eight levels – with a higher force resulting in more water movement. You can also adjust the tapping rate to a maximum of three taps per second. Settings are made using EthoVision XT software.
The Tapping Device can be combined with other add-ons and stimuli such as the white light stimulus.
Startle response analysis
To analyze the startle response of your animal, you can use the distance moved parameter measured by EthoVision XT to compare the periods before and after the stimulus.
Consistent effect throughout the well plate
The Tapping Device provides an even stimulus for all animals, no matter the location in the well plate or other testing arena. Beta testing showed no difference in response rate between animals in top versus bottom rows or in 96- versus 48-well plates.
Beta testing also showed that the startle response can be detected from the age of 3 to 9 dpf, for all stimulus intensities. Tests carried out on 5 and 6 dpf larvae showed no significant differences in the degree of response between days 5 and 6 (ANOVA, P >0.5).
*We acknowledge the kind collaboration of the following researchers and their groups: Dr. Stefan Spulber, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden; Dr. Edor Kabashi, Insitut du Cerveau et de la Moelle, Paris, France; Dr. Hiroko Nakatani, URM INSERM 788, Le Kremlin-Bicêtre, France.