Intrathoracic Injection: Compound Delivery to the Adult Zebrafish Heart

- To begin, place a wet sponge with a slit on a Petri dish. Next, anaesthetize an adult fish with tricaine solution and carefully transfer it into the slit with the ventral side facing up. Place the Petri dish under a stereo microscope and observe the movement of the beating heart under the skin.

Position a mincroinjection needle at a 45 degree angle from the body axis above the beating heart located between the operculum and the pectoral girdle. Gently, advance the needle through the skin into the pericardium, a thin membrane that surrounds the heart. Deliver the injection mix into the pericardium.

The shot contains a tracer dye such as phenol red to track the solutions movement. Withdraw the needle from the thorax. Transfer the fish immediately into the recovery tank containing system water and monitor it for complete recovery from anesthesia. In the following protocol, we will perform an intrathoracic injection to deliver a test compound and examine its effects on heart regeneration.

- Use a net to catch an adult fish and transfer it into the anesthetic solution. After one to two minutes, when the fish stops swimming and the movement of operculum is reduced, touch the fish with