The preferred items were available in all sessions individualized for each participant, while items that participants indicated an allergy to were unavailable. Participant-rated drug effect questionnaires included the Adjective Rating Scale www.selleckchem.com/products/Cisplatin.html (Oliveto et al., 1992), a Drug Effect Questionnaire that consisted of 20 items sensitive to the effects of stimulant drugs, which was developed in our laboratory (Rush, Stoops, Hays, Glaser, & Hays, 2003), and Cigarette and Food Rating Scales (Vansickel et al., 2007). Cardiovascular measures included heart rate and blood pressure. Medication Administration The drug conditions were placebo and methylphenidate (10, 20, and 40 mg). These doses were selected based on previous work showing that doses in this range reliably increase ad libitum cigarette smoking, function as discriminative stimuli, and produce positive subjective effects (Rush et al.

, 2005; Stoops, Lile, Glaser, & Rush, 2005; Vansickel et al., 2007). Each active dose of methylphenidate was tested once, while placebo was tested twice. Doses were administered orally in mixed order with the exception that the highest dose of methylphenidate was never administered during the first experimental session for safety reasons. Dose conditions were administered using double-blind conditions. Data Analysis Data were analyzed statistically as raw scores for all measures. Effects were considered significant for p �� .05. Planned comparisons were used to compare data from each of the active dose conditions to the average from the placebo conditions.

For the Adjective Rating Scale, Drug Effect Questionnaire, and cardiovascular measures, data collected after the first hour were considered uninterpretable because participants determined the amount they smoked (i.e., they smoked varying numbers of cigarettes with different nicotine contents). For this reason, only data from the first hour were used in the analyses for those measures. Results Smoking Measures The intermediate and high dose of methylphenidate increased the number of cigarette choices over money relative to placebo (absolute t10 values > 2.1, p �� .05; Figure 1). The high dose of methylphenidate increased the number of puffs per session relative to placebo (absolute t10 = 3.0, p < .05; Figure 1), while the low and high dose of methylphenidate increased peak CO (absolute t10 values > 2.2, p < .05; Figure 1).

The intermediate dose of methylphenidate produced increases in peak CO, but due to higher variability at this dose, the effect did not attain statistical significance. Figure 1. Dose effects of methylphenidate for number of cigarettes GSK-3 chosen (top left panel), number of puffs per session (top right panel), peak CO (bottom left panel), and number of food items consumed (bottom right panel). x-Axis: dose in milligrams. Data points …