Cocaine 'rapidly changes the brain'

Taking cocaine can change the structure of
the brain within hours in what could be the
first steps of drug addiction, according to
US researchers.
Animal tests, reported in the journal Nature
Neuroscience , showed new structures linked
to learning and memory began to grow soon
after the drug was taken.
Mice with the most brain changes showed a
greater preference for cocaine.
Experts described it as the brain "learning
addiction".
The team at University of California, Berkeley
and UC San Francisco looked for tiny
protrusions from brain cells called dendritic
spines. They are heavily implicated in memory
formation.
Cocaine hunting
The place or environment that drugs are taken
plays an important role in addiction.
In the experiments, the mice were allowed to
explore freely two very different chambers -
each with a different smell and surface texture.
Once they had picked a favourite they were
injected with cocaine in the other chamber.
A type of laser microscopy was used to look
inside the brains of living mice to hunt for the
dendritic spines.
More new spines were produced when the
mice were injected with cocaine than with
water, suggesting new memories being formed
around drug use.
The difference could be detected two hours
after the first dose.
Researcher Linda Wilbrecht, assistant professor
of psychology and neuroscience at UC
Berkeley, said: "Our images provide clear
evidence that cocaine induces rapid gains in
new spines, and the more spines the mice
gain, the more they show they learned about
the drug.
"This gives us a possible mechanism for how
drug use fuels further drug-seeking behaviour.
"These drug-induced changes in the brain may
explain how drug-related cues come to
dominate decision making in a human drug
user."
Commenting on the research, Dr Gerome
Breen, from the Institute of Psychiatry at
King's College London, told the BBC: "Dendritic
spine development is particularly important in
learning and memory.
"This study gives us a solid understanding of
how addiction occurs - it shows us how
addiction is learned by the brain.
"But it is not immediately apparent how useful
this would be in developing a therapy."