Addiction Key Links Cocaine With Nicotine

Part of the brain that may be important in addiction reacts the same way to nicotine that it does to cocaine, heroin and other addictive drugs, researchers have found.

Their results provide further evidence of the power that cigarettes wield over those addicted to nicotine, and offer hints at how treatments might one day break the smoking habit. The results also provide some of the best physiological evidence yet suggesting that nicotine and cocaine addictions work in similar ways.

It suggests from a neurobiological level that we're dealing with a real drug and a real brain effect," said Dr. George Koob of the Scripps Research Institute in San Diego.

Earlier research showed that nicotine stimulates the release of the neurotransmitter molecule dopamine in the brain. The new study, conducted by Italian researchers, goes a step further by demonstrating that like most addictive drugs, nicotine causes dopamine to be released in a specific region known as the shell of the nucleus accumbens, which lies between the midbrain and the forebrain.

The shell links the amygdala, which is active during emotional experiences, and the core of the nucleus accumbens, which controls some aspects of movement. Together, the three areas are believed to be central in the addiction process.

The research "adds new weight to the conclusion that nicotine is indeed addictive," wrote Dr. Leslie L. Iversen of the University of Oxford in a commentary that is appearing today with the study in the journal Nature.

President Clinton and Bob Dole, the all-but-certain Republican Presidential nominee, began trading barbs over tobacco last month. Mr. Dole, who opposes the President's efforts to regulate tobacco, has been dogged by criticism since he suggested in June that smoking was not necessarily addictive.

The new study "is not a surprise, but I think it's very timely because of the current political debate," said Dr. David Self, a neuroscientist at the Yale University School of Medicine in New Haven.

The study puts nicotine in a class with most well-known addictive drugs, including cocaine, morphine and amphetamines, said Dr. Gaetano Di Chiara, a neuroscientist at the University of Cagliari in Sardinia who led the research. "The ability to stimulate dopamine transmission is a kind of mark, a kind of label which is common to all these drugs and substances," he said.

Dr. Di Chiara and three colleagues studied the effects of two nicotine doses on rats. They found that after the higher dose, the amount of dopamine produced in the shell of the nucleus accumbens increased significantly for 20 minutes. At the lower dose, the effect lasted 10 minutes.

Nicotine also significantly increased brain activity in the nucleus accumbens after the higher dose, but not in 36 other brain areas that the researchers monitored. Those results suggest that some of the methods now used to treat cocaine addiction might work for smokers.