To begin, gently shave the buccal hair between the whisker pad and the eye of an anesthetized mouse. Fix the head of the mouse in a stereotaxic frame, or otherwise, fixate the head. Apply ointment on both eyes to avoid drying.
Scrub the shaved head area with alcohol, and then with Betadine. Under a dissecting microscope, make a four millimeter skin incision perpendicular to the midline, approximately halfway between the edge of the whisker pad and the eye, just rostral to the infraorbital foramen and centered around the line between the center of the eye and the center of the whisker pad. To expose the infraorbital nerve, bluntly separate the superficial connective tissue, minimizing musculature damage and avoiding the motor nerve fibers.
Using a rotation motion, slip the head of a hooked ligation aid under the infraorbital nerve. Place the chromic gut ligature through the hole on the tip of the ligation aid and retract the ligation aid so that the ligature remains under the infraorbital nerve, with both ends of the ligature equidistant from the nerve. Tie a slip knot from both ends of the ligature and slide it against the infraorbital nerve.
Slide the knot further to constrict the infraorbital nerve. Then place a normal knot on top of the slip knot. Cut the ends of the ligature, leaving approximately 1.5 millimeters of free ends to prevent the knot from becoming undone.
Close the skin incision using 6-0 synthetic absorbable sutures. Allow the mouse to recover on a heated pad or under an infrared heating lamp.
