Proceed to collect the brain from the previously isolated head of the fetus under a dissecting microscope. Using curved forceps, hold the snout and use a number five forceps to carefully peel off the skin from the skull cap, keeping it attached to the snout for ease of holding. Holding at about 75 degrees relative to the brain, run the forceps along the midline until the clear membrane of the developing skull parts to each side.
Shift the forceps parallel to the cranium, insert it underneath the skull cap, and pinch and peel to one side. After one side is removed, grasp the remaining side with the forceps and peel to the other side. Using a micro spoon, gently scoop the brain out of the skull.
Transfer the brain to a fresh 60 millimeter dish containing cold PBS. Using the curved forceps, hold the brain at the junction of the hindbrain and forebrain with the non-dominant hand. With the dominant hand, hold the scalpel with the blade parallel to the surface of the brain.
Then press down firmly at the mid cortical region. Still holding the hindbrain, make a second incision in front of the hindbrain to separate it from the forebrain. In the middle section, look for a small linear space on the ventral surface, which is the third ventricle.
Using number five forceps carefully pinch off the lining on either side of the ventricular surface, then transfer it to a fresh, clean, 1.5 milliliter microcentrifuge tube. Place the tube quickly into a cryo-safe container of liquid nitrogen.
