Obesity Predisposition Traced To The Brain's Reward System

“The tendency toward obesity is directly related to the brain system that is involved in food reward and addictive behaviors, according to a new study. Researchers at Tufts University School of Medicine (TUSM) and colleagues have demonstrated a link between a predisposition to obesity and defective dopamine signaling in the mesolimbic system in rats. Their report appears in the August 2008 issue of The FASEB Journal. The mesolimbic system is a system of neurons in the brain that secretes dopamine, a neurotransmitter or chemical messenger, which mediates emotion and pleasure. The release of the neurotransmitter dopamine in the mesolimbic system is traditionally associated with euphoria and considered to be the major neurochemical signature of drug addiction. ‘Baseline dopamine levels were 50 percent lower and stimulated dopamine release was significantly attenuated in the brain reward systems of obesity-prone rats, compared with obesity-resistant rats. Defects in brain dopamine synthesis and release were evident in rats immediately after birth,’ said Emmanuel Pothos, PhD, assistant professor in the department of pharmacology and experimental therapeutics at TUSM and member of the neuroscience program faculty of the Sackler School of Graduate Biomedical Sciences. Pothos says, ‘these findings have important implications in our understanding of the obesity epidemic. The notion that decreased dopamine signaling leads to increased feeding is compatible with the finding from human studies that obese individuals have reduced central dopamine receptors.’ He speculates that an attenuated dopamine signal may interfere with satiation, leading to overeating.”

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