Researchers have found that rats either seek out sweets or lose interest, depending on the action of a stomach hormone called ghrelin. Ghrelin is one of many chemicals in the body that tell the brain when to trigger hunger or fullness.
New results about this hormone's influence were presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience, held in San Diego.
Recent research showed that, in addition to moderating normal eating habits, ghrelin acts on the brain's reward and pleasure centers -- areas also activated by drugs and sex.
In this study, researchers used tests typically found in alcohol and drug addiction experiments to determine the role of ghrelin in food addiction. While rats pressed a lever hundreds of times to earn a tiny bit of sugar, rats given ghrelin worked almost twice as hard to get the same treat, as though they had not eaten. Yet when the hormone was blocked in hungry rats, they were less willing to labor for a sweet reward, as if they were full. The researchers also found that increasing or decreasing ghrelin influenced whether the animals preferred environments they associated with candy consumption. These findings may help explain why people eat when not hungry and have implications for potential weight-control treatments.
"Our results indicate that ghrelin plays an important role in food intake that is driven by the pleasure of food rather than by hunger," said lead author Karolina Skibicka, PhD, of University of Gothenburg in Sweden. "We believe that future therapies for obesity that limit the intake of sugary and fatty foods could be enhanced with drugs that suppress ghrelin's effects on the reward system."
Research was supported by the Swedish Institute, the Swedish Research Council for Medicine, the European Union 7th Framework, and ALF Göteborg.
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