Study shows why once is enough to hook some smokers

Researchers in Canada have found a region in the brains of rats that may be the key to why, for some people, one cigarette is all it takes to become hooked on nicotine, while others are repelled by it. By manipulating specific molecular doorways into receptors, they were able to control which rats in the study enjoyed or repelled their first exposure to nicotine. They found that specific receptors of the message-carrying chemical, dopamine, in the core and shell of the nucleus accumbens, controlled whether the rats enjoyed or were repelled by nicotine. When the researchers blocked two types of dopamine receptors with drugs delivered to these areas of the nucleus accumbens, the rats experienced nicotine as a positive, rewarding experience. The researchers also were able to reverse this process, making the nicotine unpleasant in rats that had the equivalent of a "pack-a-day" nicotine addiction. "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.

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