The key may lie in brain chemistry. In the brain, nicotine stimulates the release of dopamine , a chemical or neurotransmitter that allows communication between nerve cells. Dopamine transmits pleasure signals when you eat chocolate or receive a hug, for example. Nicotine addiction is not instantaneous. In fact, the first drag often makes a new smoker dizzy and nauseous, thanks to nicotine's adverse effects.
Few people realize that pure nicotine is actually quite deadly.
Nicotine is the active ingredient in some insecticides. For every cigarette a person smokes, he or she inhales about 1 to 3 mg of nicotine. Fortunately, the body quickly breaks down nicotine to keep it from building up to a fatal dose. After repeated exposure to nicotine, your body gets used to the drug. The brain creates more receptors , the parts of a nerve cell to which nicotine and neurotransmitters bind.