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All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. Animal anesthesia and surgery
- Weigh and anesthetize the mouse with your approved anesthesia regimen from your local animal care committee.
- Perform a tail or toe pinch with forceps to confirm deep anesthesia before surgery.
- Position the mouse in a stereotaxic apparatus and fix its head.
- Apply eye ointment on both eyes to keep them moist. Follow your local animal care guidelines regarding pre- and postoperative analgesia.
- Shave the hair using surgical clippers. Make a small incision (12-15 mm) in the middle of the exposed surgical area with scissors. Using forceps, gently pull the scalp away from the midline.
- Separate the skin gently and remove residual tissue. Clean the skull using hydrogen peroxide-coated cotton buds.
- Drill two small holes of radii 1.0-1.5 mm on both the skull's left and right sides to allow the recording microelectrodes to be inserted into the M2 regions under a stereomicroscope (Figure 1A).
NOTE: Stereotaxic locations of bilateral M2: 1.94 mm anterior to the bregma, 1.0 mm lateral to the midline, and 0.8-1.1 mm ventral to the dura.
- Remove the dura mater carefully with a tungsten needle.
- Pull glass borosilicate micropipettes (outer diameter: 1.0 mm) as recording microelectrodes with resistance of 1-2 MΩ.
- Insert two separate recording microelectrodes filled with 0.5 M NaCl into the holes using mechanical micromanipulators (at 60°, Figure 1B).
2. LFP recordings in bilateral M2 of mice
- Lower the left and right glass electrodes slowly into the appropriate coordinates of bilateral M2 (Figure 1C).
- For quality control, test the resistance of each electrode using the differential amplifier before capturing LFPs.
- Set the recording process at 0.1 Hz high-pass and 1,000 Hz low-pass with 1,000x amplification.
- Collect digitized raw LFP data of at least 60 s spontaneous activities in a stable state, with mice breathing evenly at a respiratory rate of 2 breaths per second under anesthesia.
- After recording, slowly raise the electrodes out of the brain, then euthanize the mice by fast cervical dislocation.
- Save the data and analyze it offline.
