BEIJING, Aug. 6 (Xinhuanet)-- Researchers in Canada have found some key clues to explain why some individuals become addicted to tobacco with their first cigarette while others are initially sickened by the experience, according to media reports Wednesday.

    The researchers did a series of experiments on rats, which have brain structures similar to humans. They identified the specific dopamine receptor subtype that controls the brain's initial sensitivity to nicotine's rewarding and addictive properties.

    By manipulating such dopamine receptors into brain, they were able to control which rats in the study enjoyed their first exposure to nicotine and which were repelled by it.

    "We were able to switch nicotine's aversive effects to rewarding effects, a finding that could be important in helping people quit smoking," said Dr. Steven Laviolette of the University of Western Ontario.

    Laviolette said "naturally occurring differences" in these receptors may account for why some people are more susceptible to nicotine addiction.

    The findings could lead to new therapies to prevent nicotine addiction and to treat nicotine withdrawal when smokers try to kick the habit.

    "If we can develop pharmacological treatments to target those regions, we can basically affect the development of nicotine addiction by controlling the brain's perception of nicotine's rewarding effects," Laviolette said.

    (Agencies)