Controlled cortical impact (CCI) TBI model of the mouse

CCI was induced in mice as previously described.³² C57BL/6 mice (8–12 week old, 160 total) were housed in standard cages with a 12-h light/dark cycle and had access to food and water ad libitum. The animal protocol was approved by the Emory University Institutional Animal Care and Use Committee (IACUC), in compliance with the National Institutes of Health (NIH) guidelines. For TBI surgery, mice were anesthetized with isoflurane (3% induction, 1.5% maintenance) and placed on a stereotaxic frame. After a midline skin incision, a 3.5-mm circular craniotomy was performed midway between the lambda and bregma, 2.0 mm to the right of the central suture using an electric microdrill (Dremel, Mount Prospect, IL). During the craniotomy, mice were excluded from the study if the dura mater was breached. CCI was induced with an electric impact device using a steel cylindrical flat impact tip. In this study, we used a PCI3000 precision cortical impactor (Hatteras Instruments, Cary, NC) and a 2.8-mm diameter impact tip (velocity = 3.0 m/sec, depth = 0.5 mm, and contact duration = 150 msec). Body temperature was maintained during surgery by a feedback-controlled homeothermic blanket (Harvard Apparatus, Holliston, MA). After the injury, the skin was sealed using Vetbond (3M, St. Paul, MN), and mice were allowed to recover in a humidity- and temperature-controlled incubator (Thermocare, Incline Village, NV). Sham animals received the craniotomy, but no impact was applied.