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."
m.bbc.co.uk/news/health-23811712

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