In vivo microdialysis

Mice were anesthetized with 2% vaporized isoflurane during surgery. An intracerebral guide cannula (cat no. CMA 11, CMA/Microdialysis AB) was then stereotaxically implanted into the left nucleus accumbens at a depth of 4.0 mm (coordinates with respect to the bregma: 1.4 mm anterior and 0.8 mm lateral). The guide cannula was secured with dental cement (cat no. GC Fuji I, GC Corporation) and then closed with a dummy cannula. Lidocaine cream was applied to the incision site after surgery for acute pain relief. After allowing at least 3 days recovery from surgery, the dummy cannula was removed and a dialysis probe (membrane length 1 mm, 6 kDa cut-off, CUP 11, CMA/Microdialysis AB) was set through the guide cannula. The probe was perfused with Ringer solution (147 mM Na⁺, 4 mM K⁺, and 155.6 mM Ca²⁺) at a flow rate of 2.0 μl/min. Microdialysis was performed under awake and unrestrained conditions, and the amounts of DA in dialysates were measured using online HPLC coupled to an electrochemical detector system (BMA-300, Eicom) according to the manufacturer’s instructions.