Cause of Nicotine Addiction: Same Enzymatic Change Shown in Cocaine and Heroin

Cause of Nicotine Addiction: Same Enzymatic Change Shown in Cocaine And Heroin

Cigarette smoking remains the leading cause of death and illness among Americans. Every year, roughly 430,000 Americans die from illnesses caused by tobacco use, accounting for one fifth of all deaths. Tobacco use costs the nation about $100 billion each year in direct medical expense and lost productivity. Almost everyone knows that smoking causes cancer, emphysema, and heart disease; that it can shorten your life by 14 years or more; and that the habit can cost a smoker thousands of dollars a year. So how come people are still lighting up? The answer, in a word, is addiction.


Smoking's a hard habit to break because tobacco contains nicotine, which is highly addictive. Like heroin or other addictive drugs, the body and mind quickly become so used to the nicotine in cigarettes that a person needs to have it just to feel normal.It is a potent neurotoxin with particular specificity to insects; therefore nicotine was widely used as an insecticide in the past, and currently nicotine derivatives such as imidacloprid continue to be widely used.In lower concentrations (an average cigarette yields about 1mg of absorbed nicotine), the substance acts as a stimulant in mammals and is one of the main factors responsible for the dependence-forming properties of tobacco smoking.

The U.S. Centers for Disease Control and Prevention estimates that 20.9 percent of all adults smoke in the United States, which adds up to 45 million people. And 23 percent of high school students smoke.Both lung cancer and emphysema would become quite rare if people would stop smoking. Compared to a nonsmoker, a smoker faces these risks:

Smoking not only increases the risk of pancreatic cancer, but can also increase blood sugar levels and reduce your body's ability to use insulin. In addition, the chemicals in tobacco can damage blood vessels, muscles and organs. This may also increase your risk of diabetes. Pregnant women who smoke have an increased risk of diabetes during pregnancy (gestational diabetes).It also develop wrinkles and yellow teeth, they also lose bone density, which increases their risk of osteoporosis (pronounced: ahs-tee-o-puh-row-sus, a condition that causes older people to become bent over and their bones to break more easily). Smokers also tend to be less active than nonsmokers because smoking affects lung power. Smoking can also cause fertility problems in both men and women and can impact sexual health in males.

As nicotine enters the body, it is distributed quickly through the bloodstream and can cross the blood-brain barrier. On average it takes about seven seconds for the substance to reach the brain when inhaled. The half life of nicotine in the body is around 2 hours[3]. The amount of nicotine inhaled with tobacco smoke is a fraction of the amount contained in the tobacco leaves (most of the substance is destroyed by the heat).Nicotine acts on the nicotinic acetylcholine receptors. In small concentrations it increases the activity of these receptors, among other things leading to an increased flow of adrenaline, a stimulating hormone. The release of adrenaline causes an increase in heart rate, blood pressure and respiration, as well as higher glucose levels in the blood.

The sympathetic nervous system, acting via splanchnic nerves to the adrenal medulla, stimulates the release of epinephrine. Acetylcholine released by preganglionic sympathetic fibers of these nerves acts on nicotinic acetylcholine receptors, causing cell depolarization and an influx of calcium through voltage-gated calcium channels. Calcium triggers the exocytosis of chromaffin granules and thus the release of epinephrine (and norepinephrine) into the bloodstream.

Smoking causes long-lasting changes in the brain similar to changes seen in animals when they are given cocaine, heroin and other addictive drugs, U.S. researchers said .

A study of the brain tissue of smokers and nonsmokers who had died showed that smokers had the changes, even if they had quit years before, the team at the National Institute on Drug Abuse reported.

"The data show that there are long-lasting chemical changes in the brains of humans," said Michael Kuhar of Emory University in Atlanta, who was not involved in the study.

"The chemical changes alone suggest a physiological basis for nicotine addiction."

A team led by Bruce Hope of NIDA, one of the National Institutes of Health, analyzed levels of two enzymes found inside brain cells known as neurons.

These enzymes help the neurons use chemical signals such as those made by the message-carrying compound dopamine.

Smokers and former smokers had high levels of these enzymes, the researchers reported in the Journal of Neuroscience.

Hope said other studies had seen the same thing in animals given cocaine and heroin -- and it was clear that the drugs were causing the effects.

"This strongly suggests that the similar changes observed in smokers and former smokers contributed to their addiction," he added in a statement.

Experts on smoking have long said that nicotine is at least as addictive as heroin.

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