Addictive Properties of Nicotine

Boston Globe on 7/18/96:

Authors say new study confirms nicotine's addictive properties

Adding further evidence for the addicting power of tobacco, a new study reveals that nicotine targets the same "reward system" in the brain as cocaine, amphetamines and morphine, and that it stimulates the brain in the same way those drugs do.

Like those addicting drugs, nicotine speeds up activity in a part of the brain that harbors nerves influencing emotions and motivation, the scientists said.

It also triggers the brain's release of a chemical messenger, dopamine, which has been been linked to the addicting effects of other drugs.

Published as a letter in today's issue of the journal Science, the report from Italian researchers strengthened the conclusion of most addiction specialists about nicotine's similarity to other drugs that incite compulsive use and abuse.

By chance, the report comes as GOP presidential candidate Bob Dole has become entangled in a debate about nicotine's status as an adductive drug. "You know, there is a mixed view among scientists and doctors whether it's addictive or not," Dole told NBC's Katie Couric in an interview earlier this month. "I'm not certain it's addictive."

Alan Leshner, director of the National Institute on Drug Abuse, declined to comment on Dole's assertions, but in an interview said of the new report: "In the scientific community there is fundamentally no question about nicotine's being addicting. this study reinforces the commonality between nicotine's physiological effects and those of other addicting substances."

The US Surgeon General declared nicotine an addicting drug in 1988.

The Italian researchers, headed by Gaetano Di Chiara at the University of Cagliari, previously had reported that nicotine injected into rats targets a structure in the brain called the nucleus accumbens. "Most if not all drugs abused by humans stimulate dopamine transmission in the nucleus accumbens," the scientists wrote in the letter Nature.

The newest research goes further. The scientists implanted tine, hair-like electrodes in the brains of rats to more precisely track the action of nicotine. They demonstrated that nicotine spurred the secretion of dopamine in a specific part of the nucleus accumbens, known as the shell, and also caused specific cells in the shell to use more energy.

These findings, the researchers said, show that nicotine shares with other addictive drugs this very specific activity in the brain - activity that scientists believe is critical to the drugs' addictive power. In fact, when scientists deliberately damage nerves in that tine structure, rats that had been trained to self-administer nicotine stop giving themselves the drug.

Leslie L. Iversen, a pharmacologist at the University of Oxford in England, wrote in an accompanying article that the Italian research "adds new weight to the conclusion that nicotine is indeed addictive."

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