Rethinking chemical signals in bird brains
A group of researchers, led by Gregory Ball of the Department of Psychological and Brain Sciences, has uncovered evidence for an intriguing kind of chemical crosstalk in the brain. Their finding - that the neurotransmitter dopamine interacts with a class of receptors normally associated with a different neurotransmitter - provides an exception to a basic principle of neuroscience.
Since dopamine's discovery in 1952 by two Swedish researchers, the conventional wisdom has been that it binds uniquely to dopamine receptors. This, in turn, has been sine qua non for studying the role of dopamine in neurological disorders like Parkinson's disease as well as the neural basis of drug addiction, motivation and pleasure.
Indeed, this principle - that a neurotransmitter will only bind to its own complementary class of receptors - is a central tenet of modern neuroscience. Scientists expect that serotonin will bind to serotonin receptors, acetylcholine to acetylcholine receptors, and so on.
Nonetheless, a host of recent research has hinted that dopamine may, in fact, interact with other kinds of receptors. Until now, however, no hard evidence has yet been uncovered. Towards this goal, Ball and his colleagues chose to study one receptor, the alpha-2-adrenergic receptor, in the zebra finch brain.
The choice of a bird was not random. "Zebra finches are songbirds that possess a specialized neural circuit that controls the learning and production of song," Ball said.
The potential for dopamine to bind to other receptors seems especially likely in the brains of songbirds, including the zebra finch. The neural systems that produce the complex series of vocalizations comprising a bird's song have been mapped out in great detail.
This fact has allowed specific pathways and areas in the songbird's brain to be linked to specific aspects of a bird's song. More important to the present study, lots of dopamine and dopamine-like molecules have been shown to be highly concentrated in the bird brain's song-production areas.
Since dopamine's discovery in 1952 by two Swedish researchers, the conventional wisdom has been that it binds uniquely to dopamine receptors. This, in turn, has been sine qua non for studying the role of dopamine in neurological disorders like Parkinson's disease as well as the neural basis of drug addiction, motivation and pleasure.
Indeed, this principle - that a neurotransmitter will only bind to its own complementary class of receptors - is a central tenet of modern neuroscience. Scientists expect that serotonin will bind to serotonin receptors, acetylcholine to acetylcholine receptors, and so on.
Nonetheless, a host of recent research has hinted that dopamine may, in fact, interact with other kinds of receptors. Until now, however, no hard evidence has yet been uncovered. Towards this goal, Ball and his colleagues chose to study one receptor, the alpha-2-adrenergic receptor, in the zebra finch brain.
The choice of a bird was not random. "Zebra finches are songbirds that possess a specialized neural circuit that controls the learning and production of song," Ball said.
The potential for dopamine to bind to other receptors seems especially likely in the brains of songbirds, including the zebra finch. The neural systems that produce the complex series of vocalizations comprising a bird's song have been mapped out in great detail.
This fact has allowed specific pathways and areas in the songbird's brain to be linked to specific aspects of a bird's song. More important to the present study, lots of dopamine and dopamine-like molecules have been shown to be highly concentrated in the bird brain's song-production areas.
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