Induction of Traumatic Brain Injury in a Rat Model Using a Lateral Fluid Percussion Device

Place an anesthetized rat on a stereotaxic frame.

Make a midline incision and retract the skin to expose the skull.

Disinfect the skull, dry the surface, and scrape it to flatten the target area for cannula placement.

Drill a hole and remove the bone flap to expose the dura mater, the brain's outer covering.

Clean the skull with a swab.

Place a cannula over the hole and secure it with dental cement.

Fill it with artificial cerebrospinal fluid to prevent the dura mater from drying.

Connect the rat to the tubing of the lateral fluid percussion device, which consists of a pendulum and a fluid-filled reservoir.

As the rat regains the withdrawal reflex, release the pendulum from a calibrated angle to strike the reservoir, generating a pressure wave that hits the brain.

The pressure damages blood vessels and causes neural cell death, leading to traumatic brain injury.

Allow the rat to recover to assess the injury-induced neurodegeneration.

Make a 1.5 to 2.5-centimeters midline incision through the skin and muscle of the scalp using a number 10 scalpel blade. Retract the skin and muscle to expose the skull and provide a clear surgical field. Electric cautery is useful for achieving quick hemostasis.

Next, shave down the lateral ridge of the left parietal bone, using a surgical curette to produce a smooth, flat surface so that the base of the female-female Luer Lock hub can rest flush with the skull. Irrigate the skull surface and surrounding tissues with 2.0 mg per milliliter gentamicin solution in sterile saline, and blot excess solution with sterile swabs. Then apply 3% hydrogen peroxide to the skull to dry the bone.

At this point, create a 5-millimeter diameter craniectomy site through the left parietal bone. Then, remove the bone flap with the surgical curette and smooth tissue forceps.

Next, using a stereomicroscope, gently remove the thin rim of bone remaining with smooth tissue forceps taking care not to rupture the dura. Then swab the skull with 70% ethanol to remove any bone dust, and to dry the skull. Apply a thin layer of cyanoacrylate glue around the bottom edge of the Luer Lock hub, and secure it to the skull over the craniectomy without obstructing the opening and without allowing the glue to contact the dura. Then seal the Luer lock in place with a thin layer of glue around the outside base of the hub.

Next, prepare a slurry of dental cement and apply this to the surface of the skull around and over the base of the Luer Lock hub to secure it in place. Then fill the Luer Lock hub with a sterile, preservative-free solution containing multiple electrolytes using a syringe and needle. A convex bolus of saline should be seen above the top of the rim. Once the dental cement is completely cured, discontinue gas anesthesia and remove the rat from the stereotaxic frame.

Place the rat on a platform next to the fluid percussion injury device in sternal recumbency. Then, secure a 12-centimeter length of pressure tubing to the end of the device's curved tip, with the opposite end terminating in a 2-centimeter male Luer Lock twist connector. Secure the rat to the device by connecting the female end of the hub on the rat skull to the male connector.

Repeatedly check the animal for return of withdrawal reflex. As soon as the rat regains withdrawal reflex, but is still sedated, release the pendulum of the device to cause a single 20-millisecond pressure pulse and induce injury. Then immediately disconnect the rat from the FPI device, place it in sternal recumbency, and provide supplemental oxygen via a nose cone until spontaneous breathing returns.

Note that apnea is an anticipated consequence of the injury. If necessary, provide periodic manual breaths via a bag valve mask until the rat begins to spontaneously breathe on its own. Monitor continuously and record the time of return of righting reflex.