EVIDENCE SHOWS DAMAGE TO BRAIN FROM COCAINE USE

Same Cells That Trigger High Destroyed

Cocaine attacks and destroys the same brain cells that trigger the "high"
that cocaine users get from the drug, according to new research that
provides the first direct evidence of the effect on the brain's pleasure
center.

"This is the clearest evidence to date that the specific neurons cocaine
interacts with don't like it and are disturbed by the drug's effects," said
Dr. Karley Little, an associate professor of psychiatry at the University
of Michigan and chief of the VA Ann Arbor Healthcare System's Affective
Neuropharmacology Laboratory.

Little and his colleagues took autopsy brain tissue samples from 35 known
cocaine abusers and 35 non-drug users of about the same age, sex, race and
causes of death. The researchers measured several indicators of the health
of the patient's dopamine brain cells, which release a pleasure-signaling
chemical called dopamine. These cells interact with cocaine.

In all three measures of dopamine activity, the levels were significantly
lower for cocaine users than control subjects. Levels tended to be lowest
for cocaine users with depression.

"The questions we now face are whether the cells are dormant or damaged, is
the effect reversible or permanent and is it preventable?" explained
Little, lead author of a paper on the results published in the January
issue of the American Journal of Psychiatry.

In recent years, many researchers have come to suspect that chronic cocaine
use causes the brain to adapt to the drug's presence by altering the
molecules involved in dopamine release and re-uptake, and in the genetic
instructions needed to make those molecules.

The new study gives the most conclusive evidence yet that dopamine neurons
are harmed by cocaine use.

Dopamine, Little explained, triggers the reactions needed to repeat
previous pleasure. More than just drug "highs," the chemical helps drive
people to eat, work, feel emotions and reproduce.

Normally, when something pleasurable happens, dopamine brain cells pump the
chemical into the gaps between themselves and related brain cells. Dopamine
finds its way to receptors on those neighboring cells, triggering signals
that set off pathways to different feelings or sensations.

Dopamine neurons in the brain's pleasure center die off at a steady rate
over a person's lifetime. Severe damage is a hallmark of Parkinson's
disease, causing a loss of movement control.

When first taken, cocaine has a disruptive effect on the brain's dopamine
system. It blocks the transports that return dopamine to its home cell
after its signaling job is done.

But with nowhere to go, dopamine builds up in the connection zone and keeps
binding with other cells' receptors, sending pleasure signals out over and
over again. This causes the intense cocaine high most users report.

With extended use of cocaine, the brain's response to the drug is reset and
drug taking at first pursued for pleasure moves to drug taking to avoid the
negative feelings that come in the absence of cocaine.