Zebra II as A Novel System to Record Electrophysiological Signals in Zebrafish

Our research group at UC Irvine develops novel tools to provide electrophysiological assessment in zebrafish with better performance and longer duration. Our system have been used to study cardiac genes and carry out drug screening using zebrafish. The current challenges in electrophysiological zebrafish experiments rely on short recording times, which can be less than five minutes.

This extends the experiment duration, which restricts the sample size and affects the experiment length. Our technique enables up to an hour recording of multichannel ECG, and it's expandable to EEG, while others are limited to one channel in five minutes. Well, I think it's how to utilize the zebrafish cardiac optical data, correlating the electrocardiography, to study the cardiac pathology and developmental abnormality, especially in the context of preclinical drug development.

I think how to leverage our expertise that we develop in optical, electrical, and chemical sensing along with artificial intelligence in using zebrafish as a cost-effective animal model to develop drugs in a preclinical stage for cardiovascular medicine, neurology, neuropsychology, and pain medicine. To begin, equally divide 40 fish into four groups and house them in separate tanks. Connect the Zebra2 device to a power source and initiate operation with the red button located on the front panel.

Navigate through the device's touchscreen to choose the chamber to be configured. Adjust the low-filter setting to 0.1 hertz and the high-pass filter setting to 500 hertz and set the gain to 10, 000. Lift the front lid to access the four chambers prior to starting the experiment.

Immerse each chamber's sponge in tricaine solution and squeeze out any excess liquid. Rotate the four-electrode array to ensure the sponge is accessible before introducing the fish. For the treatment, dissolve 258.13 milligrams of amiodarone in one liter of deionized water.

Insert a magnetic stirrer into the container and stir until the solution is completely dissolved and clear. Dilute the amiodarone stock solution To prepare 70, 100, and 200 micromolar working solutions in fish water. Submerge the fish individually in the respective amiodarone solution for exactly five minutes.

To begin, treat the fish with appropriate concentrations of amiodarone. After anesthetizing the fish, place it onto the sponge with the ventral side up. Position the preset electrode array in a rhombus shape over the chest area of the fish to capture signals from four different points simultaneously.

Then, rotate each electrode, lowering the pin until it makes contact with the fish's underside. If the pin is too high, turn the corresponding thumbscrew clockwise to lower it until it touches the fish. Close the chamber lids once all electrode arrays are correctly positioned over the fish in the operational chambers.

To mark each chamber for recording, select it on the touch screen, then initiate the recording with the Record button on the screen. After two minutes, click the Stop button and then click Save from the prompt window that pops up. Depending on your specific research needs, save the information either on a disc or to the cloud.

To begin, initiate electrocardiogram or ECG acquisition of the amiodarone-treated fish. For troubleshooting, press the Stop button on the device interface to halt the recording process and identify the channels with inconsistent signals. Lift the front lid to access the electrode chambers and identify the chamber and specific electrodes causing the issue.

Turn the top thumbscrew clockwise to adjust the electrode's proximity to the fish, lowering the electrode closer to the fish. If merely moving closer does not solve the issue, rotate the electrode to a different spot on the fish until a satisfactory signal is achieved. The control group displayed a consistent heart rate of around 120 beats per minute and a QTc interval of 330 milliseconds, showing normal ECG patterns.

Amiodarone treatment resulted in a dose-dependent increase in QTc interval, extending from 365 milliseconds at 70 micromolar to 546 milliseconds at 200 micromolar and a corresponding decrease in heart rate from around 105 beats per minute at 70 micromolar to 84 beats per minute at 200 micromolar.