Dopamine conducts a frenzied song of craving at one end of a tiny brain region and a panic-stricken hymn at the other. Depending on where along the length of the region the neurotransmitter is triggered, it mediates emotions ranging from desire to disgust, a new study shows.
"The roles [of dopamine] maybe partitioned, and perhaps defined, by anatomy," comments Emily Hueske, a neuroscientist at MIT.
The study brings researchers one step closer to explaining how dopamine performs a spectrum of functions. Dopamine interacts with spatially coded signals so that its output varies depending on where it's acting, the team reports in the July 9 Journal of Neuroscience.
In the long term, the finding suggests how drugs might be developed to treat dopamine-mediated disorders such as drug addiction, obesity and anxiety.
Kent Berridge, a neuroscientist at the University of Michigan in Ann Arbor, and his colleagues set out to understand how dopamine could lead to desire for a reward, and then turn around and cause fear, pain and stress.
Berridge's team focused on the nucleus accumbens, a smallbrain structure known as the pleasure center in mammals. The researchers tampered with dopamine and the brain chemical glutamate, known to interact with dopamine, along the length of the nucleus accumbens of rats. Allowing dopamine to act normally, the researchers injected a glutamate blocker into the front end of the brain area, turning normal rats into binge-eaters. But when the team disrupted glutamate at the back end, the rats stopped eating and became fearful--kicking up sand at the bottom of their cages, as wild rodents are wont to do when a snake or a scorpion is in their midst, Berridge says. …