Ask a smoker what they get out of cigarettes and they are likely to talk about pleasure, contentment, and an overall good feeling. Nicotine, the active ingredient in cigarettes, is a stimulant. Used in low doses like those delivered by combustible cigarettes, stimulants activate the nervous system, resulting in enhanced arousal and alertness. Nicotine binding in the limbic system — the part of the brain that houses the pleasure and reward center — releases dopamine, resulting in feelings of euphoria. These effects combine to give smokers a boost in their mood.