(−)-Nicotine hydrogen tartrate [0.4 mg/kg, 5-min injection-to-placement interval (IPI)], varenicline dihydrochloride (0.1 and 1.0 mg/kg; 30-min IPI), dihydro-β-erythoidine (DHβE; 1.0 and 3.0 mg/kg; 45-min injection-to-placement interval; IPI), and methyllycaconitine (MLA; 3.0 and 10 mg/kg; 45-min IPI) were obtained from Sigma Aldrich (St. Louis, MO; nicotine, DHβE, and MLA) or NIDA (Bethesda, MD; varenicline) and dissolved in 0.9% saline. All injections were at 1 mL/kg. As per field standards, nicotine dose is reported as base form; all other drug doses are reported as salt form. The pH for nicotine was adjusted to 7.0±0.2 with a NaOH solution. All doses and IPIs were based on published research, including previous work from our laboratory (Levin et al., 2012 (link), Liu et al., 2010; Pittenger et al., 2017 (link); Wooters et al., 2009 (link)). Nicotine was injected s.c; all other drugs were injected i.p.