According to the National Institute on Drug Abuse, or NIDA, once a cigarette smoker inhales a puff of smoke from the cigarette, it takes 8 seconds for the nicotine to travel to the brain. Once in the brain, nicotine causes multiple changes in brain chemistry, including the release of brain chemicals that cause pleasurable feelings, which make smoking cigarettes highly addictive.
Acetylcholine Release
The shape of the nicotine molecule is remarkably like the shape of a normal brain chemical called acetylcholine. Acetylcholine is normally present in the brain in moderate amounts, and attaches to an acetylcholine receptor much like a key fits into a lock. According to NIDA, this key-in-lock process results in rapid physiological changes, such as an increase in heart rate, blood pressure and rate of breathing. Over the long-term, these effects can lead to cardiovascular problems, according to the Center for Substance Abuse Research at the University of Maryland. These effects contribute to chronic high blood pressure, also called hypertension, a weakened heart, heart attacks and stroke.
Dopamine Release
Besides acetylcholine receptors, nicotine molecules also attach to cholinergic receptors on cells in the brain, according to NIDA. This interaction results in the release of another brain chemical called dopamine. Dopamine is normally released during pleasurable activities, such as eating tasty food, engaging in fun activities or seeing people you love.
Ingesting nicotine, whether by smoking or chewing tobacco, causes an unnatural spike in the level of dopamine in the brain, which, in turn, causes chemically induced pleasurable feelings. This release of dopamine is the reason why people can become addicted tobacco after smoking only a few cigarettes, according to the Center for Substance Abuse Research. In addition to causing pleasurable feelings, dopamine release in the brain is also associated with feeling motivated, and thus people may feel that smoking cigarettes helps them accomplish tasks.
Inhibition of GABA
John Easton, the director of Medical Center Communications at the University of Chicago, wrote an article published by the “University of Chicago Chronicle" in March 2002 that offers insights into how nicotine affects the brain. Mr. Easton reviewed several studies that show that not only does nicotine cause the release of the pleasure-causing dopamine in the brain, but it also blocks the natural reaction in the brain that inhibits dopamine. During pleasurable activities, the brain releases a chemical called GABA that naturally blocks the effects of dopamine and reigns in the excitement caused by dopamine. However, Mr. Easton reports that nicotine blocks the release of GABA. Thus, nicotine blocks the body's natural process of dampening the effects of dopamine, which results in a longer duration of pleasurable feelings. This prolonged feeling of pleasure is another reason why nicotine is so highly addictive.
