Sunday, October 12, 2008

Dopamine stimulation causes withdrawal

A New State of Mind

The importance of dopamine was discovered by accident. In 1954 James Olds and Peter Milner, two neuroscientists at McGill University, decided to implant an electrode deep into the center of a rat's brain. The precise placement of the electrode was largely happenstance: At the time the geography of the mind remained a mystery. But Olds and Milner got lucky. They inserted the needle right next to the nucleus accumbens (NAcc), a part of the brain dense with dopamine neurons and involved with the processing of pleasurable rewards, like food and sex.

Olds and Milner quickly discovered that too much pleasure can be fatal. After they ran a small current into the wire, so that the NAcc was continually excited, the scientists noticed that the rodents lost interest in everything else. They stopped eating and drinking. All courtship behavior ceased. The rats would just cower in the corner of their cage, transfixed by their bliss. Within days all of the animals had perished. They had died of thirst.

It took several decades of painstaking research, but neuroscientists eventually discovered that the rats were suffering from an excess of dopamine. The stimulation of the brain triggered a massive release of the neurotransmitter, which overwhelmed the rodents with ecstasy. In humans addictive drugs work the same way: A crack addict who has just gotten a fix is no different from a rat in electrical rapture. This, then, became the dopaminergic cliché — it was the chemical explanation for sex, drugs, and rock 'n' roll.

But that view of the neurotransmitter was vastly oversimplified. What wasn't yet clear was that dopamine is also a profoundly important source of information. It doesn't merely let us take pleasure in the world; it allows us to understand the world.

I have yet to see anyone "cower with bliss" and it is funny that it took 30 or so years to make the research fit the supposition (cliche is right). Speaking of rats and drugs, the Rat Park experiments were very interesting.


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