Surgery

Each rat was anesthetized initially with isoflurane (to effect) followed by ketamine (80-100 mg/kg, intraperitoneal (IP)) and xylazine (5-10 mg/kg, intramuscular (IM)). Anesthesia was maintained throughout the procedure with repeated bolus injections of ketamine (10-15 mg/kg/ IM) as needed. After the rat was secured in the stereotaxic frame, bupivacaine (0.5-1.0 mL) was delivered subcutaneously (SC) to the scalp/incision area and penicillin (0.15 mL; G benzathine and G procaine, 300 K/mL) was delivered SC under the skin of the back. A rectal probe attached to a homothermic blanket (Harvard Apparatus, Holliston, MA) was used to maintain core body temperature at approximately 36.7⁰C throughout the experiment. A craniectomy was made based on stereotaxic coordinates relative to bregma over the PM contralateral to the reaching forelimb (anterior-posterior (AP) +3.5 mm, medial-lateral (ML) +2.5 mm) and the M1 ipsilateral to the reaching forelimb (AP +0.5 mm, ML + 3.5 mm). To control brain edema after the craniectomy, the muscles of the neck overlying the cisterna magna were reflected and a small puncture was made in the spinal dura (foramen magnum) to allow for CSF drainage. Six holes (three on either side of the skull midline) were drilled caudal to the M1 craniectomies for placement of stainless steel screws used during the procedure to ground the electrodes and anchor them to the skull with dental acrylic. The dura was then removed over the exposed PM and M1. ICMS was used to identify the forelimb motor representations (Figure 1B). Following completion of the surgical procedure, the incision was closed with sterile 4.0 silk surgical suture and treated topically with EMLA cream, and triple antibiotic ointment. The rat was removed from the stereotaxic device and the temperature probe removed and placed within the homeothermic blanket, upon which the animal was monitored for anesthetic recovery. Each rat received an additional injection of penicillin 0.15 mL SC (G benzathine and G procaine 45,000 IU), and then was moved to a recovery area until the rat was able to maintain an upright posture and locomote freely. Once stabilized, the rat was returned to its home cage. Post-surgery analgesics were given to the rat during the 72 hours after surgery [four SC injections of Buprenorhpine (0.05-0.10 mg/kg every 12 hours; four doses of Acetaminophen (20-40 mg/kg, oral) every 12 hours].