Effects of nicotine on subjective arousal may be dependent on baseline subjective state.

The often disparate and contrasting effects of nicotine on subjective arousal in smokers may be due in part to differences in presmoking subjective state. In Study 1, on each of 2 days, 10 male smokers were divided into high- and low-baseline subgroups on the basis of median split of resting predrug baseline subjective arousal. Then, subjects received intermittent nicotine (15 mu/kg) or placebo via measured-dose nasal spray, with drug conditions counterbalanced between days. In Study 2, 32 male and female smokers were similarly divided into high- and low-baseline subgroups on subjective arousal prior to either smoking or sham-smoking (n = 16 each) during a single session. Results were virtually identical between studies in showing that subjective arousal responses to nicotine (Study 1) or smoking (Study 2) were significantly inversely related to baseline arousal level; those initially low in arousal showed large increases following nicotine or smoking whereas those high in arousal showed little change. No such baseline dependency of responses was seen following placebo or sham smoking. Baseline dependency of cardiovascular responses to nicotine or smoking was also evaluated in similar fashion to determine generalizability of these effects to nonsubjective responses. In each study, systolic blood pressure response was related to baseline level but there was no effect of baseline level on heart rate and diastolic blood pressure responses. Implications of these results for explaining differential rewarding effects of smoking are discussed.