BETHESDA, MD (NIH) -- NIDA-supported researchers from Brookhaven National Laboratory and the State University of New York at Stony Brook have found evidence in humans that dopamine plays a role in the conditioned cue response to food. Cues-seeing, smelling, and tasting something enjoyable-increase the desire for the reward without necessarily enhancing the pleasure of the reward itself.

Positron emission tomography (PET) was used to measure changes in dopamine in the brains of 10 healthy adults (eight men and two women) during food and neutral stimulations. Food stimulation consisted of the participants viewing, smelling, and tasting their favorite foods but not actually eating the foods. For neutral stimulation, participants described their family genealogy in detail. Prior to and during food stimulation, participants were instructed to rate their feelings of "hunger," "desire for food," "alertness," "stimulation," and "talkativeness" on a scale of 1 to 10. Participants had fasted 16-20 hours before PET scans were conducted.

Food stimulation caused an increase in dopamine in the dorsal striatum but not in the ventral striatum, where the nucleus accumbens is located. This suggests that dopamine may be involved in food motivation that is distinct from its role in regulating food's reward effects through the nucleus accumbens. Previous research has linked increases in dopamine in the nucleus accumbens, the reward center of the brain, with addiction.

The finding that dopamine may play a role in cue-induced effects could have important implications in drug addiction research. Many individuals addicted to drugs, especially cocaine and nicotine, are susceptible to cue-induced cravings. A better understanding of the biological basis of cue-related behaviors may provide better insights in the development of more effective behavioral and pharmacological treatments for drug addiction.