2.2 Surgery for cannula implantation
Rats were anesthetized with isoflurane anaesthesia (5% induction and 2% maintenance) and placed in a stereotaxic frame. A unilateral and a bilateral guide cannula (OD 0.64 mm×I.D. 0.25 mm, CC 1.2 mm, RWD Life science Co Ltd., Shenzhen, China) were chronically implanted in the lateral ventricle (-0.8 mm AP; -1.5 mm ML; -3.5 mm DV) and mPFC (PrL: +3.2 mm AP; ±0.60 mm ML; −2.6 mm DV, IL: +3.2 mm AP; ±0.6 mm ML; −3.8 mm DV) (Paxinos & Watson, 1986), respectively. The cannula and three anchor screws were bonded to the skull with dental acrylic and dental cement. After surgery, rats were placed in a heated pad and observed for at least 30 min, then returned to its original cage. Rats were handled and checked for signs of pain and distress at least once daily. Topical analgesic (lidocaine/prilocaine cream) was used to prevent signs of pain and/or discomfort for at least 2-3 days. The rats were intramuscularly injected with penicillin (400000 IU kg-1) for at least 3 days and allowed to recover for 7 days before the experiments began.