Nicotine is a naturally occurring compound in tobacco products and is the chemical that makes tobacco addictive. When nicotine is introduced to the body, it rapidly gets into the bloodstream. It can cross the "blood-brain" barrier and reach the brain within 10 to 20 seconds of inhalation.
Smokeless tobacco, which is held in the mouth for long periods, is particularly addictive because it releases much more nicotine than inhaled smoke.
Once the nicotine gets into the brain, it increases the flow of the brain chemical transmitter dopamine, creating a pleasurable response. Nicotine also increases alertness and suppresses appetite, which is part of its attraction. When blood levels begin to fall, people crave it and experience withdrawal symptoms.
Research from Brown University shows that nicotine itself can cause cardiovascular disease by promoting the invasion and damage of smooth muscle cells that line blood vessels. This process ultimately leads to the formation of artery-clogging plaques.
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