Nicotine blocks nerve receptors in the brain that would otherwise stop the body from feeling the pleasurable effects of smoking, a new study suggests.

Scientists have known that when nicotine binds to nerve receptors, it spurs feelings of reward that promote addiction, said study researcher Paul Kenny, an associate professor at Scripps Research Institute in Florida. To do this, the molecule mimics a natural chemical called acetylcholine.

The new study shows that at the same time, other nerve receptors work like a stop sign and inhibit feelings of reward. But certain gene mutations can make these stop signs work less efficiently than the reward nerve receptors, he said.

"What you're left with is a persistent reward system ," Kenny told MyHealthNewsDaily.

Kenny and his colleagues gave nicotine to rats with these gene mutations and found that they consumed far more nicotine than rats without the gene mutations.

These particular gene mutations are inherited; they aren't the result of DNA damage from smoking, Kenny said. But the more people smoke, the less functional those stop sign receptors might become, he said.

"If you have damage to these receptors, no matter how much nicotine you take, it's always rewarding," he said.

This new finding shows that increasing the activity of the nerve receptors that work as stop signs could stop smoking cravings, Kenny said. This approach would be different from current smoking cessation drugs like varenicline (commonly known by brand name Chantix) that work by blocking the nerve receptors that promote feelings of reward.

Now, Kenny is working to develop a drug that would enhance the brain's stop signal receptors.

The study was published online Jan. 30 in the journal Nature.

Pass it on: Nicotine doesn't just spur feelings of pleasure and reward; it also stops the brain from inhibiting those feelings of pleasure and reward.

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