DRUG'S A TURNOFF?

U Of T Study Finds Way To Aid Addicts

Researchers may have found the secret to controlling the addiction process
in people hooked on alcohol, drugs or other vices. Scientists at the
University of Toronto have discovered a molecular addiction switch in the
mammalian brain that has the potential of controlling the addiction process
in drug users.

The study finds that the region of the brain called the VTA contains
receptors that, when exposed to a certain enzyme, can control the switch
from addicted to non-addicted state and back again.

This finding goes against the previous ideas that viewed drug addiction as
a permanent change in the brain, said lead author Steven Laviolette, who
conducted the research while he was a PhD student at U of T's department of
anatomy and cell biology with senior author Prof. Derek van der Kooy.

Manipulating A Switch

"Our findings suggest instead of a permanent alteration in the brain,
there's actually a switch that goes on between two separate systems,"
Laviolette said.

He explains that the first system mediates the brain's responses to drugs,
while one is not yet addicted. The second system mediates the brain's
responses to drugs once one has become addicted.

"They also suggest we may be able to manipulate the switch
pharmacologically to take drug addicts back to a non-addicted state in a
relatively short period of time so they do not crave the drug," Laviolette
said.

The switch is a brain receptor known as GABA-A. An enzyme -- carbonic
anhydrase -- produced by the body controls how the receptor behaves. In
studies with rats, the researchers were able to manipulate the enzyme with
a drug to control whether it could turn the switch on or off.

A Matter Of Hours

Without this intervention, the brain can switch back to a non-addicted
state following a period of withdrawal from drugs -- a process often
measured in weeks. By manipulating the enzyme pharmacologically, that
return to a non-addictive state in rats has been reduced to a matter of
hours. "The same anatomical pathways that we are manipulating in rats, also
exist in humans, so we hope this will be applicable to human drug addiction
as well," Laviolette said.

The study is published in Nature Neuroscience.