Effects of mecamylamine on spontaneous EEG and performance in smokers and non-smokers

In a previous study, mecamylamine, a centrally active nicotine antagonist, exacerbated EEG signs of tobacco abstinence in abstinent smokers. In the present study, the effects of mecamylamine were compared in non-smokers and nondeprived smokers. Mecamylamine (0, 5 and 10 mg, p.o.) was administered to six smokers and six non-smokers; eight of these subjects were also given a 20 mg dose. Before drug administration, resting EEG was similar in both groups. In both groups, mecamylamine caused dose-related decreases in alpha frequency and increases in delta frequency; beta frequency was increased by the 5 and 10 mg doses. The similarity of effects in smokers and non-smokers suggests a direct pharmacological action rather than precipitated nicotine withdrawal. Significant baseline differences existed between smokers and non-smokers in systolic blood pressure, pulse rate, skin temperature and pupil diameter. Response time slowed in both vigilance and distractibility tasks and delayed recall was impaired. Mecamylamine increased ratings of: "relaxed," "nodding," "sleepy" and "coasting." This small-sample study tentatively suggests that nicotinic cholinergic mechanisms modulate brain electrical activity and cognitive function in smokers and non-smokers. Disruption of these neural systems could mediate the symptoms of tobacco withdrawal and be involved in the pathophysiology of Alzheimer's disease.