Electroencephalography Recording in a Rat Model of Focal Epilepsy

Take an anesthetized rat with focal epilepsy, characterized by abnormal brain electrical activity.

Secure the rat in a stereotaxic apparatus and administer anesthesia through a nose cone. 

Completely remove the head fur to prevent signal interference during electroencephalogram, or EEG recording.

Clean the skin with alcohol and place saline swabs to enhance electrical conductance.

Apply EEG paste to each electrode of a multichannel EEG mini-cap to ensure optimal conductivity between the electrodes and the skin.

Fix the mini-cap on the scalp.

Position the ground and reference electrodes on the ears.

Connect the mini-cap to the amplifier. Visualize the EEG signals to identify loosely connected electrodes and improve their connectivity.

Administer a sedative and stop the anesthetic flow to minimize its interference with brain activity.

Record the EEG and identify the abnormal electrical activity events.

Mark the mini-cap's position on the skin for spatial correlation during subsequent brain imaging.

To begin this procedure, mix EEG electrode paste with 0.9% NaCl solution. Add a drop of methylene blue to help to visualize the electrode paste inside the electrodes and on the skin. Next, place the mixed paste in a syringe, and make sure that there are no air bubbles in it. Then, fill all 32 electrodes with the paste from the bottom without introducing any air bubbles.

As part of the preparation procedure for the rat, trim the rat's head. Afterward, reduce the isoflurane to 2%. Then, place the rat on the heating pad in the stereotaxic apparatus. Fix the ear canals with the ear bars and secure the nose cone for the supply of anesthetic. Next, apply ophthalmic ointment to the eyes of the animal.

Subsequently, shave its head, and rub the skin with 90% isopropyl alcohol to stimulate the blood vessels and remove the grease. Then, place a saline swab on the scalp and cover it completely to keep good skin conductance, until the EEG mini-cap is ready to be placed. Connect the respiration, temperature, and three-lead electrocardiogram probes to the rat's body to continuously monitor its physiology during the recording procedure.

In this procedure, remove the saline swab on the rat's scalp, and place the prepared EEG mini-cap on its skin. Fix the mini-cap with rubber bands. Apply a layer of high-conductance electrode paste on both the ground and reference electrodes. Subsequently, place them on the respective ears. Then, connect the EEG mini-cap to the amplifier. Look at a preview of the EEG traces and check the performance of all electrodes.

Then, administer Dexdomitor at 0.25 milligrams per kilogram to the rat intraperitoneally, and immediately reduce the isoflurane rate to 0%. If the respiration rate is not within 30 to 60 BPM range, increase the isoflurane rate gently at the maximum of 1%. Now, begin EEG recording and verify the existence of paroxysmal activity in the EEG traces. After the recording, mark the positions of the three jutting circles of the EEG mini-cap on top of the skin by inserting a color pen inside them before the EEG mini-cap is removed. Take a picture of the rat head with the landmarks.