Rationale: Smoking following overnight abstention reliably increases heart rate (HR), an effect due to nicotine absorption. The effect of subsequent cigarettes on HR is less than that associated with the first cigarette of the day, an indication of tachyphylaxis (acute tolerance). To date, smoking/HR studies have not been conducted double-blind. Instead, control conditions have included non-smoking or some type of "sham" smoking (puffing on an unlit cigarette or a straw).
Objective: We investigated the HR response to smoking and its time course using double-blind methodology.
Methods: HR was recorded in overnight-abstaining participants before and after smoking the first, second and third cigarette of the day (40 min between each cigarette) in two sessions. The experimental manipulation involved replacing the second cigarette of one session with a very low nicotine-yield cigarette (0.05 mg; FTC method) compared with the other five cigarettes (1.1-mg nicotine yield).
Results: Smoking increased HR by 15, 8 and 7 beats/min (bpm) in the session where all three cigarettes had the higher yield. The comparable values for the session in which the second cigarette had the lower yield were 15, -1 and 11 bpm.
Conclusions: In the session where all three cigarettes had the higher yield, larger increase in HR after smoking the first than the second or third cigarettes indicates tachyphylaxis. The HR response in the other session was smaller for the third cigarette than the first cigarette, indicating that a period greater than 80 min would be needed before the HR response was fully restored.