Ethanol and sucrose solutions were prepared in tap water using 95% (v/v) ethanol (Gold Shield Chemical Co., Hayward, CA, USA). Blood ethanol concentrations were analyzed using a nicotinamide adenine dinucleotide (NAD)-alcohol dehydrogenase (ADH) spectrophotometric assay (Sigma-Aldrich, St. Louis, MO, USA). Nicotine solutions were prepared using (−) nicotine hydrogen tartrate salt (Sigma-Aldrich, St. Louis, MO, USA) dissolved in saline (vehicle) and administered subcutaneously (s.c.) .Varenicline (6,7,8,9-tetrahydro-6,10-methano-6H pyrazino[2,3-h][3]benzazepine tartrate) (Coe et al., 2005) was generously provided by Pfizer Global Research and Development (Groton, CT) and dissolved in saline (vehicle) and administered subcutaneously (s.c.). All drug solutions were prepared immediately before each injection and administered in a volume of 1 ml/kg.
