To establish a dose-effect curve for nicotine's abuse potential as a function of nicotine dose and delivery rate. Pulsed IV nicotine administration will be used as it closely matches nicotine delivery by inhaled tobacco use.

Both sub-studies will enroll male and female tobacco cigarette smokers. This study will examine the feasibility of the proposed study parameters in a total of 10 completers. In a crossover design, participants will be tested under 5 conditions: 0.2 mg nicotine delivered over 2.5 minutes (5 pulsed-nicotine deliveries), 0.2mg nicotine delivered over 10 min (20 pulsed-nicotine deliveries), 1.0 mg nicotine delivered over 2.5 minutes (5 pulsed-nicotine deliveries) and 1.0 mg nicotine delivered over 10 min (20 pulsed-nicotine deliveries). The main outcome measures will be self-report drug effects and urges to smoke cigarettes.

The investigators hypothesize that the abuse potential and alleviation of smoking urges are produced by nicotine as a function of nicotine dose and delivery rate.

This study is complete with 13 enrolled and 10 completers

Inclusion Criteria:

• Female and male smokers, aged 18 to 35 years, who have been smoking tobacco cigarettes for at least a year
• smoke ≥ 5 and less than 20 cigarettes per day
• urine cotinine levels > 100 ng/mL consistent with nicotine intake of an active smoker
• not seeking treatment at the time of the study for nicotine dependence
• in good health as verified by medical history, screening examination, and screening laboratory tests; and 6) for women, not pregnant as determined by pregnancy screening, nor breast feeding, and using acceptable birth control methods.

Exclusion Criteria:

• History of major medical or psychiatric disorders that the physician investigator deems as contraindicated for the subject to be in the study
• regular use of psychotropic medication (antidepressants, antipsychotics, or anxiolytics)
• current alcohol or substance dependence for any other recreational or prescription drugs other than nicotine
• use of e-cigarettes more than 10 days in the past 30 days
• urine drug screening indicating recent illicit drugs use (with the exception of marijuana)

Participant will not know nicotine dose or rate of infusion.