A Stereotactically Guided Ablation Technique for Auditory Cortex Removal in Rats

Take an anesthetized rat secured in a stereotactic frame.

Shave and disinfect the scalp, then make an incision to expose the skull.

Identify the anatomical references the bregma, the lambda, and the interaural line to locate the auditory cortex, the brain region that processes sound signals.

Incise and retract the temporal muscle, revealing the temporal bone.

Position a needle at the interaural line's midpoint. Using this landmark, determine the coordinates above the auditory cortex.

Drill the marked region and remove the bone to expose the brain.

Cut through the meninges, the layers covering the brain.

Perform ablation by aspirating the cortical layers while preserving the white matter. Auditory cortex removal disrupts the sound signal processing ability.

Replace the excised bone, apply gauze to control bleeding, and suture the skin.

Apply antibiotic ointment to prevent infection and administer subcutaneous analgesics to alleviate pain.

Allow the rat to recover to assess the impact of ablation.

To begin this procedure, place the anesthetized rat on a heating pad to maintain its body temperature. Then stabilize the animal's head in a stereotaxic frame using two ear bars and a bite bar. Shave the scalp and disinfect the surgical area with povidone iodine.

Using a scalpel, make an incision along the midline to expose the skull, and retract the periosteum covering the surface of the cranium. After that, use a sterile cotton tip to gently remove any blood covering the surface of the skull in order to visualize bregma, lambda, and the interaural line. Make an incision in the temporal muscle near its dorsal insertion on the skull with a scalpel. After that, pull the muscle out using a needle and suture material and fix the suture material to the stereotactic frame in order to expose the temporal bone.

Slowly lower a sterile straight needle until it is right above the surface of the skull, so that the tip of the needle is set at interaural zero. Set this point as zero. Following that, target the AC using four points. Then lower the needle to right above the temporal bone to visualize each of these four points. Mark the points with a marker on the temporal bone and connect them in order to draw a rectangle. The rectangle will serve as a guide to open a window in the bone.

In this procedure, open the window using an electric drill and a small drill bit. Drill the perimeter of the rectangle at 8,000 RPM until the bone gives away. Cool the drilling surface by rinsing it with cold sterile saline to prevent damage to subcortical structures. When the bone gives way, be careful not to drill into the brain.

When the borders are loose, pull up the covering bone with fine forceps and store it in cold sterile saline. Using a surgical microscope, gently cut the meninges with a microsurgical knife and remove them using two fine-pointed forceps. If bleeding occurs, rinse the surgical site with cold sterile saline.

Next, gently aspirate the AC using a surgical suction device coupled to a sterile 20-gauge blunt tip needle. Aspirate only the six cortical layers and not the underlying white matter. This point is critical and needs to be performed very carefully. When the aspiration is finished, cover the surgical site with the extracted bone and apply an absorbable hemostatic gauze.

Let the temporal muscle recover its original position, and then suture the skin using wound clips. After that, apply antibiotic ointment to the wound. Subsequently, inject buprenorphine subcutaneously in the back of the rat as an analgesic, one hour and eight hours after the end of the surgery. Keep the animal on the heating pad until it wakes up, and return it to its housing cage for recovery.