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- In zebrafish larvae, a visual stimulus can activate somatosensory neurons and trigger an escape response. There are two types of such neurons found in the larva, trigeminal and Rohon-Beard neurons. We can manipulate the activity of these neurons by modifying them to express transgenic light-sensitive ion channels. This approach is called optogenetics.
To perform this technique, mount a transgenic larva with the dorsal side facing up in agarose gel and place it under a dissecting microscope. Use a razor blade to detach a wedge-shaped portion of agarose from around the yolk and tail. Fill this area with egg water. Pull the agarose away from the trunk and tail of the larva.
Position the tip of an optic cable near the trunk where the cell body of the Rohon-Beard neuron is located. Deliver a pulse of blue laser light. Upon exposure to the blue light, the transgenic light-sensitive ion channels in the neuron's membrane open, allowing ions to enter, triggering an action potential that elicits the escape response. Record the larva's behavior using a high-speed camera.
In the example protocol, we will mount the larvae to activate the Rohon-Beard neuron, expressing a channelrhodopsin varia
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