The Telegraph
Since 1st March, 1999
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Pleasure button lies in your belly
- Hormone may help develop drugs to control craving for food, party pills

New Delhi, Oct. 19: Maybe it’s not such a good idea to dismiss gut feelings. The stomach, it turns out, can indeed influence the brain, even rewire its circuits.

A hormone produced in the stomach activates the same set of brain cells that are also stimulated by delicious food, sexual experience and party drugs, researchers announced today.

A new study by the researchers at the Yale University School of Medicine in the US has shown that the hormone called ghrelin directly affects the pleasure and reward circuits of the brain, and may play a role in the sensation of craving.

Through experiments on mice and rats, Yale neurobiologist Tamas Horvath and his colleagues have shown that ghrelin activates a cluster of brain cells that provide the sensation of pleasure and expectation of reward.

Their findings, reported today in The Journal of Clinical Investigation, might help scientists develop novel drugs to suppress cravings — whether for calorie-rich food or recreational drugs.

Previous studies have shown that delicious food, sexual experience or recreational drugs all lead to an increase in the secretion of a chemical called dopamine by cells in a region of the brain called the ventral tegmental area (VTA). The cells in the VTA play a role in mechanisms that underlie reward-seeking behaviour.

“Ghrelin has a direct effect on this reward- seeking circuitry,” Horvath told The Telegraph in a telephone interview.

“Not only does the hormone activate increased dopamine secretion in the VTA, it can also rearrange connections between brain cells in the region. What that tells us is that the VTA is not hard-wired. It is plastic,” he said.

The findings are similar to the discovery by the Yale team earlier this year that ghrelin has a powerful and rapid influence on the hippocampus, a region of the brain associated with spatial learning and memory.

The earlier experiments — also on mice and rats — had shown that ghrelin produced in the stomach can enter the hippocampus and alter connections between the brain cells within this region. Studies on the behaviour of the animals showed that the changes in the brain circuits there are linked to enhanced learning and memory.

The highest levels of ghrelin are in circulation early in the day when the stomach is empty. Horvath had presented his findings on how ghrelin affects the hippocampus earlier this year in Nature Neuroscience.

The observations in animals suggest that the best learning may occur on an empty stomach. “A practical recommendation could be that children may benefit from not overeating at breakfast in order to make the most out of their morning hours at school,” Horvath had said earlier this year after publishing the findings on the hippocampus.

Ghrelin has long been known to control appetite. In the latest study, the researchers found that the infusion of ghrelin into the VTA of rats increased their food intake. However, rats infused with molecules that prevent ghrelin from entering VTA brain cells consumed less food even after a 24-hour fast.

These findings raise the prospect of designing molecules that might be able to control craving for fat-laden food or recreational drugs. “It’s a long-term goal,” Horvath said.

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