Brain's Opioid Receptors -- or Endorphin System -- May Hold Key to Treatment Possibilities for Bulimia Patients

"Involvementof the opioid system may explain the addictive quality of thisbehavioral disorder," said Angela Guarda, M.D., assistant professor ofpsychiatry at Johns Hopkins School of Medicine in Baltimore, Md. Thefirst imaging study to implicate the opioid system in bulimia nervosashows differences in women with bulimia compared to healthy women,added J. James Frost, M.D., Ph.D., professor of radiology andneuroscience at Johns Hopkins and co-author of "Regional μ-OpioidReceptor Binding in Insular Cortex Is Decreased in Bulimia Nervosa andCorrelates Inversely With Fasting Behavior." In the study, eight womenwith bulimia were compared to healthy women of the same age and weight.Their brains were scanned using positron emission tomography (PET)after injection with the short-acting radioactive compound carfentanil,which binds to mu-opioid receptors in the brain, explained Frost. PETis a powerful medical imaging procedure that noninvasively uses specialimaging systems and radioactive tracers to produce pictures of thefunction and metabolism of the cells in the body. He noted, "We foundthat mu-opioid receptor binding in bulimic women was lower than inhealthy women in the left insular cortex. The insula is involved inprocessing taste, as well as the anticipation and reward of eating, andhas been implicated in studies of other driven behavioral disorders,including drug addiction and gambling.”

Bulimia nervosa is aserious eating disorder marked by a destructive pattern of recurrentdieting, binging and vomiting to control one's weight. "Patients feeltrapped by this behavioral cycle suggesting something about it isrewarding,” said Guarda, “and, as with substance abuse, the course ofbulimia is frequently chronic and relapsing."

Bulimia nervosa,which is 10 times more common in females than in males, affects 1–2percent of adolescent girls and young women in the United States.Bulimia may become chronic and lead to serious health problems,including seizures, irregular heartbeat, dental erosion, swollensalivary glands, gastrointestinal irritation and electrolyteimbalances. In rare cases, it may be fatal. While the cause of bulimianervosa is still unknown, research shows that certain brain chemicalsmay function abnormally in bulimia patients. This research may point toa molecular target for development of more effective treatments thanthose currently available. Frost indicated that medications that affectthe brain’s opioid receptor system and approaches to treatment forsubstance abuse disorders may be helpful in treating bulimia.

Frostand Guarda co-authored "Regional μ-Opioid Receptor Binding in InsularCortex Is Decreased in Bulimia Nervosa and Correlates Inversely WithFasting Behavior" with Badreddine Bencherif, M.D., Hayden T. Ravert,Ph.D., and Robert F. Dannals, Ph.D., department of radiology, and CarloColantuoni, Ph.D., department of neuroscience, all at Johns HopkinsUniversity School of Medicine, Baltimore, Md.