ROLE OF DOPAMINE IN DOUBT

Study Questions Previous Theory
That Chemical Is Key Player In Brain'S
Process Of Producing Enjoyment

Dopamine may not be the brain's "feel-good" chemical after all, a
study found, suggesting that scientists trying to unlock the secrets
of drug addiction may have been off target for the past two decades.

The naturally produced brain chemical, rather than being the key
player in the pleasure process, is only a messenger and one of several
factors, according to the study, published today in the journal Nature.

"It certainly says the picture is much more complicated than being
just dopamine alone, and it will lead to the search for other chemical
substances in the brain," said the study's author, chemist R. Mark
Wightman of the University of North Carolina-Chapel Hill.

Dopamine, first discovered in 1957, came into prominence in the early
1960s when scientists discovered that several antipsychotic drugs
targeted it. In the late 1970s, researchers began looking into its
role in drug addiction and found that cocaine, heroin and other
addictive drugs increase levels of dopamine in the body.

Since then, some scientists have tried to develop a medication that
would cure cocaine addiction by blocking dopamine.

The latest study is another in a series that have cast doubt on that
approach.

The researchers attached electrodes to the brains of rats, which
produced dopamine when they were shocked. The rats were then trained
to shock themselves.

As the rats continued to shock themselves, however, the researchers
discovered that the amount of dopamine produced by their brains
decreased - even though they continued to seek pleasure by pressing
the lever.