Nicotine is carried by tar particles to the alveoli of the lungs and then to the brain – a process that takes approximately 10 seconds for each inhalation11. Nicotine binds to nicotinic cholinergic receptors in the brain, leading to neurotransmitter release12, which makes smoking and smoking cues (e.g., the sight of cigarettes) more attractive and powerfully reinforcing 12. In addition, tolerance or neuroadaptation occurs with chronic smoking, resulting in proliferation of nicotinic receptors, permitting heavier levels of self-administration. Nonoccupancy of these receptors due to decreased smoking results in withdrawal symptoms such as craving, negative moods, and restlessness, which spur a return to smoking13. About half of phenotypic variance in tobacco dependence is attributable to genetic influence14.
