Nicotine free base

Alcohol solutions were prepared from ethyl alcohol (200 Proof, OmniPur, EM Science; Gibbstown, NJ) in saline to a concentration of 0.2 g/ml, and injected via intraperitoneal (i.p.) route in a volume of 10 ml/kg body weight, yielding a dose of 2 g/ kg of ethanol. Nicotine free base from MP Biomedicals, Inc. (Solon, OH, USA) was dissolved in saline (0.025 mg/ml) and injected subcutaneously (s.c.) in a volume of 10 ml/kg body weight, yielding a dose of 0.25 mg/kg of Nicotine free base. Amphetamine sulphate (Sigma/Aldrich) solutions (0.1 and 0.3 mg/ml) were prepared in saline and injected (i.p.) in a volume of 10 ml/kg body weight to yield doses of 1 and 3 mg/kg, respectively. The solutions were made daily prior to each conditioning and on the test day for state-dependent conditioned place preference (CPP).