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."