Inducing Ischemia via Middle Cerebral and Common Carotid Artery Occlusion in a Rat Model

Begin with a restrained, anesthetized rat with a loosely sutured right common carotid artery, or CCA, in the neck region.

This CCA branches into the middle cerebral artery, or MCA,  supplying oxygenated blood to the brain.

Reposition the rat laterally and make an incision between the right eye and ear.

Retract the skin and dissect the muscle to expose the skull. Position a saline dripper and aspirator for washing.

Drill over the skull and remove the bone flap. Next, cut the protective layer to expose the MCA.

Using diathermy forceps, apply heat to coagulate the right MCA at multiple points, then cut it at the vein crossing point.

Coagulation causes arterial occlusion, reducing oxygenated blood flow to the brain, induces ischemia, and leads to neuronal death.

Cover the exposed brain.

Re-expose the neck, then tightly ligate the right CCA. This prevents the permanent blood flow to the MCA and intensifies the ischemia.

Incise the skin at the midpoint between the right orbit and the external auditory canal. Next, blunt dissect the temporalis muscle to reveal the skull. Then, using up to five elastic 3 millimeter hook retractors, retract and pin the skin to the cork board. Then, place a thumb wheel adjusted gravity-driven saline drip above the open site at the highest point of the skull near the ear, and set up an aspirator system with a nozzle at the lowest point to remove any bone debris and to clear any minor bleeding from the exposed site.

Adjust the wheel to visualize the source of bleeding as necessary. Now, use a dental drill with a coarse 1.6-millimeter diamond coated drill burr at approximately 8,000 RPM to perform a 5 millimeter by 5 millimeter craniotomy on the exposed region, taking care to apply circular and lateral but not downward pressure during the drilling. When it becomes completely transparent, use forceps to remove the bone. Then, using a homemade dural hook, carefully open the dura, taking care to avoid rupturing the large surface blood vessels.

Next, use a pair of angled jeweler diathermy forceps with 0.25-millimeter pointed tips to coagulate the MCA from where the inferior cerebral vein crosses to the point of the artery bifurcation and then along the caudal branch of the MCA, until the vessels are fully occluded. Then to confirm the occlusion is complete, use microvascular scissors to cut the section of the occluded MCA that lies beneath where the inferior cerebral vein crosses the MCA. Now, cover the exposed area with a saline-soaked gauze pad, and return the rat to the supine position. Reopen the loosely tied suture on the neck to re-expose the carotid arteries, and tie a knot in the suture around the artery on the same side as the occluded MCA to permanently ligate the vessel.