STUDY ON COCAINE'S AFFECT ON BRAIN

A single, small dose of cocaine triggers a weeklong surge of activity in
the brain that may prime the user for addiction, scientists report.

Researchers at the University of California at San Francisco said
exposure to the drug accelerates a molecular process that is important
to the formation of memories and underlies addiction.

Their study appears in the latest issue of the journal Nature.

The UCSF team used slices of brain tissue from mice that were given
cocaine. The samples were taken from the ventral tegmental area of the
brain.

The VTA is rich in dopamine, a neurotransmitter associated with pleasure
that is normally released in small amounts as a biochemical reward to
brain cells. It also is associated with the high that cocaine induces
and subsequent drug cravings that travel neuron pathways throughout the
brain.

The UCSF team reported that samples from the cocaine-treated mice showed
a chain reaction in brain cells that changed the properties of a neuron
receptor named AMPA for as long as a week, long after the obvious high
is gone.

The prolonged AMPA activity triggered the release of dopamine and left
the brain primed for more of the same, they said.

These pathways typically are used in the formation of memories and
learning, but the cocaine hijacks them, they said.

"What's so amazing is that all dopamine neurons are affected by this
single cocaine exposure," said Mark Ungless, the study's lead author.
"It would have a profound effect on other areas of the brain,
particularly those involved with addiction."

The researchers said this pathway in the brain might offer one
explanation into the biochemistry of how recovering drug addicts can
relapse easily. And, they speculated, the reaction might also apply to
other addictive substances, including nicotine and alcohol.