The influence of nicotine on performance, mood, and physiological parameters as related to smoking habit, gender, and suggestibility.

Based on previous observations that sensory suggestibility might be related to cholinergic drug effects, and that individual susceptibility to nicotine as defined by response differences to various doses is lower in males, nonsmokers, and highly suggestible subjects, the present study investigated whether nicotine serum blood levels, cardiovascular responses, and sensory suggestibility show differences according to gender and smoking habit, and whether differences in nicotine susceptibility measured by a discrimination task by subjective ratings on activation can be reproduced in the direction predicted by the previous data. In a double-blind threefold cross-over design 48 subjects divided according to smoking habit, gender, and sensory suggestibility were tested in balanced order under the influence of an oral dose of 0, 0.014, or 0.028 mg/kg body weight of nicotine. Results revealed higher serum levels of nicotine in males and smokers, a dose-dependent increase in heart rate and systolic and diastolic blood pressure, partly interacting with gender or smoking habit (females and nonsmokers showing larger increase with the low doses), and a change in suggestibility in the expected direction (decrease with the low dose, increase with the large one only in female nonsmokers). A fourfold interaction among dose, smoking habit, gender, and suggestibility for the discrimination task partly reproduced the observations of higher nicotine susceptibility in females and non-smokers, whereas suggestibility did not seem to reveal the expected changes. Also, on a subjective level larger doses were necessary to make male smokers feel activated, while the other groups showed the biphasic response pattern to the two nicotine doses. In conclusion, the data justify further research on the concept of nicotine susceptibility defined by biphasic effects of nicotine on vigilance.