Study reveals clues to cigarette addiction

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.

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Study: Oxygen free radicals may help weight control

The brain's appetite center uses fat for fuel by involving molecules of oxygen free radicals associated with aging and neurodegeneration that could help in weight control, according to researchers at Yale School of Medicine.

"In contrast to the accepted view, the brain does use fat as fuel," said Tamas Horvath, a professor in the Departments of Obstetrics, Gynecology & Reproductive Sciences. "Our study shows that the minute-by-minute control of appetite is regulated by free radicals, implying that if you interfere with free radicals, you may affect eating and satiety."

The results also imply, added Horvath, "that each time a feeling of fullness or satiety is reached during a meal, you may be chipping away some time from your maximum lifespan as the most free radicals are produced when satiety-promoting brain cells are active."

Horvath and colleagues conducted the study in mice to better understand how the brain mediates neuronal activation in response to ghrelin, a hormone produced in the stomach and previously associated with growth hormone release, appetite, learning and memory.

They found that ghrelin-induced increase in appetite is driven by burning fat in hypothalamic mitochondria, which produces free radicals that are scavenged by a mitochondrial protein called uncoupling protein 2 (UCP2)

"The timing of taking antioxidants may be critical for the control of appetite," said Sabrina Diano, co-author and associate professor. "If taken on an empty stomach antioxidants may further increase appetite, however when taken with food, they may affect satiety. Further studies are needed to determine whether any regiment of orally taken antioxidants could be used to control appetite in animals and humans."

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