Potency and time course of the discriminative stimulus effects of and (A, D) (±)-mecamylamine (0.32 – 1.8 mg/kg, i.m.), (B, E) (−)-nicotine (0.1 – 1.0 mg/kg, i.m.), and (C, F) varenicline (0.1 – 1.0 mg/kg, IM) in rhesus monkeys (n=3) trained to discriminate methamphetamine (0.18 mg/kg, i.m.) from saline. Upper vertical axes : percent methamphetamine-appropriate responding. Lower vertical axes : rates of responding in responses per second. Horizontal axes: time in min after injection. Symbols above “S” and “M” represent the group averages for all training sessions preceding test sessions when the saline- and methamphetamine-associated keys were correct, respectively. Filled symbols indicate statistical significance compared to saline within a given time point (p < 0.05). Numbers in parentheses indicate the number of subjects contributing to that data point if < 3 subjects and indicative of a time point where a monkey failed to complete at least one ratio requirement during the response period.