0.22 mm syringe filter

(−)Nicotine-hydrogen-tartrate (Sigma-Aldrich, St. Louis, MO) was dissolved in saline, the pH was adjusted to 7.0 (±0.2), and the solution was filtered through a 0.22-mm syringe filter (Fisher Scientific, Pittsburgh, PA). AM4113 (N-piperidin-1-yl-2,4-dichlorophenyl-1H-pyrazole-3-carboxamide) was synthesized at the Center for Drug Discovery, Northeastern University, Boston, MA. AM4113 was dissolved in dimethylsulfoxide, Tween 80, and saline as previously described (Hodge et al., 2008 (link); Sink et al., 2010 (link)). Rimonabant [SR141716; N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide)] (NIDA Drug Supply Program, Bethesda, MD) was dissolved in methyl cellulose and Tween 80. The different doses of AM4113 (0, 0.3, 1, 3, and 10mg/kg) and rimonabant (0, 1, 3, and 10mg/kg) were i.p. administered using a counterbalanced within-subject design (acute treatment) 60 minutes prior to the start of the session (administration volume: 1mL/kg) (Sink et al., 2008 (link); Cluny et al., 2011 (link)). For chronic studies, treatment consisted of the repeated administration of the same dose.
Yohimbine was obtained from Sigma-Aldrich and dissolved in distilled water. The doses of Yohimbine and the pretreatment time were based on previous studies (Marinelli et al., 2007 (link); Le et al., 2009 (link)).