2.2. Drugs

JWH015, a cannabinoid 2 receptor (CB2) agonist (CB₂ K_i = 13.8 nM, 30 to 80 fold selectivity versus CB₁) was obtained from Cayman Chemical (Ann Arbor, MI). JWH015 was dissolved in a vehicle solution of 10% dimethyl sulfoxide, 10% Tween-80, and 80% saline (Sigma, St. Louis, MO). The mu-opioid agonist (MOR) morphine sulfate was purchased from the NIDA Drug Supply program (Rockville, MD) and was dissolved in saline. Formalin solution was obtained by diluting 1.5% of formaldehyde in saline. Ketamine:xylazine (80 mg/kg: 12 mg/kg; Phoenix Pharmaceutical, St. Joseph, MO) was used to anesthetize animals in order to insert microdialysis probes into the nucleus accumbens. The antibiotic gentamicin (Phoenix Pharmaceutical, St. Joseph, MO) was provided as a single subcutaneous dose (8mg/kg). Drugs were weighed out and dissolved in vehicle daily, prior to use. Cocaine hydrochloride was purchased from the NIDA Drug Supply program (Rockville, MD) and used as a positive control in microdialysis and HPLC studies. Finally, 5% and 2.5% isofluorane (Sigma, St. Louis, MO) mixed in 2.5 L/min of oxygen was delivered through a nose cone and used to induce and maintain anesthesia, respectively, for paw incision and SNI surgeries.