Mechanism Behind Addiction and Obesity Discovered

Natural stimuli such as food and sex release the neurotransmitter dopamine in the brain. Drugs like cocaine and heroin (and even highly caloric foods) cause the same release of dopamine, making people feel rewarded. This suggests that dopamine plays a role in both addiction and the development of obesity.

When an animal in the wild knows it can expect rewarding stimuli (such as food) in a certain location, it’s called “conditioned place preference”—this depends on spatial memories being formed in the part of the brain called the dentate gyrus.

Professor Bill Colmers of the Faculty of Medicine & Dentistry at the University of Alberta and his colleagues wanted to find out if dopamine has an effect on the memory-forming brain cells in the dentate gyrus. They used living brain slices from rats and mimicked the brain cell activity of animals exploring a new environment. When dopamine was introduced, excitability in the dendrites of the brain was increased. However, a brain chemical called neuropeptide Y had the opposite effect, decreasing excitability.

The researchers then examined a model called long-term potentiation, a form of cellular learning. When stimulating dopamine receptors, the researchers found that the cellular learning was strengthened. When adding neuropeptide Y to dopamine, long-term potentiation didn’t occur.

The researchers repeated this experiment with brain slices taken from human patients undergoing therapy for temporal lobe epilepsy. The human brain cells underwent the same cellular learning after stimulation as the rat brain cells.

Colmers said this study unveils a new reward aspect to specific places (such as a refrigerator). He added that people know there are rewarding things in the fridge, and they can find it in their sleep—which some people do.

The study’s results help explain the biology of a form of learning that could lead to new, effective treatments for both addiction and obesity.

Source: Science Daily, Mechanism Involved in Addictions and Some Forms of Obesity Discovered, October 4, 2010

 

Posted on October 6th, 2010

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