To begin place an anesthetized mouse on a fresh surgical drape. Apply ophthalmic ointment to the animal's eye to prevent dryness, then inject Metacam, followed by 0.5 milliliters of saline subcutaneously into the mouse. Shave the neck of the mouse at the base of the occipital bone, and wipe down the surface with sterile PBS.
Transfer the mouse to the stereotaxic frame in the prone position. Place the nose bar from the stereotaxic frame on top of the mouse to provide stability, and ensure the upper teeth are fastened. Position the animal head at a 120 degree angle from the body to elevate and distend the nape.
Next, using sterile gauze, clean the surgical site three times with Betadine scrub and 70%ethanol. Then wipe once with Betadine solution. Using a scalpel, make a small one centimeter incision.
Carefully run the scalpel along the midline to cut through the muscles. Using forceps, gently pull the muscles apart to the left and the right. Then load the Hamilton syringe with 2.5 microliters of elastase avoiding air bubbles.
Slowly insert the syringe with the bevel facing upward into the center of the cisterna magna. After puncturing, carefully withdraw the bevel to facilitate the release of a small amount of cerebrospinal fluid or CSF. Next, reinsert the bevel to the puncture site and slowly inject elastase or vehicle into the cisterna magna, leaving the needle in place for one minute to prevent elastase leakage.
After removing the bevel, close the incision site with a non-absorbable surgical suture, and turn off the anesthetic. Remove the animal from the stereotaxic frame and place it on a 37 degree Celsius heat pad until the mouse recovers.
