For surgical implantation of the OMPs and ICV guide cannulae, animals were anesthetized via isoflurane inhalation (5% for induction / 3% maintenance). OMPs were implanted subcutaneously approximately 3 cm below the right shoulder blade and attached via polyvinylchloride tubing to a unilateral guide cannula implanted via stereotaxic surgery. The cannula guides connected to the OMPs were counterbalanced for hemisphere using the coordinates AP -0.8, DV -4.7, ML±1.7 from bregma (Paxinos and Watson, 2005) and bilateral guide cannulae (22 gauge; Plastics One, Roanoke,) were implanted using the coordinates AP -0.8, DV -3.9, ML ±1.5 (from bregma according to Paxinos and Watson, 2005). Prior to the implantation of the OMPs, the pumps were filled with the appropriate solution (FN-439 or aCSF), attached to ICV cannulae and incubated in sterile 0.9% NaCl at 37°C for 72 hours. The coordinates for the acute condition were modified slightly based on the histological results from chronic treatment condition. For both conditions, stainless steel screws served as anchor points and cannulae were held in place using dental acrylic. The bilateral guide cannulae were sealed by inserting obdurators
