Impact of Direct Current Stimulation on Evoked Epileptic Seizures in Mouse Brain Slices

Take a mouse brain slice containing the medial thalamus, or MT, projecting to the anterior cingulate cortex, or ACC.

Secure the slice in a multielectrode array chamber perfused with oxygenated aCSF to record electrical signals.

Place positive and negative electrodes and apply direct current stimulation, or DCS, generating an electric field across the slice.

Disable DCS and place an electrode in the MT. Deliver a stimulus to evoke action potentials in the thalamic neurons, triggering neurotransmitter release.

The neurotransmitters trigger ion influx in ACC neurons and generate electrical signals, termed stimulation-evoked synaptic responses.

Reactivate DCS to monitor its effects on ACC synaptic responses.

Next, deactivate DCS and introduce seizure-inducing drugs.

The drugs increase neuronal excitability, causing the thalamic stimulus to produce continuous bursts of signals in the ACC, termed evoked epileptic seizures.

Finally, reactivate DCS to evaluate its effect on seizures by measuring the reduction in seizure amplitude and duration.

In this procedure, ensure the generation of uniform electric fields by passing currents between two parallel silver chloride-coated silver wires that are placed inside the MEA chamber. If there are no issues, the DCS should stay between 0.5 and 2 milliamps.

Next, turn off the DCS and stimulate the thalamus with a tungsten electrode. To obtain maximal synaptic responses in ACC, record 10 to 20 responses and average them. Then, turn on the DCS and stimulate the thalamus simultaneously. Evaluate the amplitude changes of the thalamic stimulation-evoked ACC response during DCS.

Now, turn off the DCS. Add 250 micromolar 4-AP and 5 micromolar bicuculline to the perfusion solution, and wait two to three hours. If the drugs affect the brain slice, the slice should produce cortical seizure responses. Subsequently, collect 10 to 20 anterior cingulate cortical responses and measure the amplitude and duration of the electrically-evoked evoked cortical seizure responses.

Next, turn on the DCS and stimulate the thalamus simultaneously. Evaluate the changes in the amplitude and duration of the evoked cortical seizure responses during DCS application. After that, replace the perfusion solution with fresh aCSF to wash out the drugs.