This article details the methodology for recording electrical activity from spiral ganglion neurons using a multielectrode array (MEA). The process includes preparing the MEA, stimulating neurons, and analyzing the resulting signals.
Begin with a spiral ganglion neuron culture on a multielectrode array, or MEA.
The MEA consists of recording electrodes connected to contacts via a circuit.
Wash the MEA to remove media and dry the contacts to avoid moisture-induced noise during recording.
Mount the MEA on its holder and install it in the recording setup.
The MEA contacts align with the holder connectors that transmit electrical signals to the recording setup.
Add an extracellular environment-mimicking solution, allowing normal physiological activity in the neurons.
Begin recording. The electrodes detect spontaneous signals or action potentials generated by the neurons, visualized as spikes on the software interface.
Now, apply an electrical pulse to one electrode exhibiting spontaneous activity.
The pulse generates an electric field, stimulating the neurons on neighboring electrodes.
Record the stimulation-dependent activity.
Finally, add a neurotoxin that blocks voltage-gated ion channels, preventing action potential generation.
Record the signal to identify background noise.
After a collective 18 days of culture, wash the MEA culture with the extracellular solution prepared earlier at room temperature. Then, dry the contacts of the MEA chip with a piece of tissue, and mount the MEAs on the MEA holder. Finally, install the MEA on the recording setup.
Afterward, add 300 microliters of the extracellular solution, and wait for 10 minutes to allow the system to stabilize before recording. Now, record the spontaneous activity for two minutes from all electrodes, and identify the active electrodes. Then, identify the electrodes responding to stimulation.
To exclude the stimulation artifact, stimulate from the same electrode 10 times. If the culture responds at least eight out of 10 times, it can be assumed as a positive response upon electrode-induced stimulation. To identify background noise, apply TTX to the culture at a concentration of one micromolar to block the voltage-gated sodium channels, and then record for two minutes.
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