http://www.newscientist.com/article.ns?id=dn9171&feedId=online-news_rss20
How Prozac affects the brain
22:00 15 May 2006
NewScientist.com news service
Jessica Marshall
A new mouse model may help explain exactly what happens in the brain in
response to antidepressants like Prozac. The research may hold huge
potential for understanding and screening new treatments for depression.
And the wide variety of existing treatments may have more in common than
was previously thought, the researchers suggest.
Prozac (fluoxetine), one of the most common drug treatments for depression,
acts by stimulating the growth of new neurons in the brain’s hippocampus.
Grigori Enikolopov and his team from Cold Spring Harbor Laboratory in New
York, US, wanted to narrow down which steps in this growth process, called
neurogenesis, Prozac was influencing.
So the team engineered mice with nuclei in their nerve cells that glow
green during neurogenesis. This made it easy to count and compare the
number of developing neurons. By tracking other factors associated with
different stages of neurogenesis, Enikolopov’s team found that only one
step was influenced by Prozac.
The drug did not promote neuron growth by stimulating stem cells, but
rather by stimulating the division of cells just "downstream" of the stem
cell, called amplifying neural progenitor cells, which have already
committed to becoming neurons.
Tailored treatments
Now the researchers are testing a range of treatments – from different
drugs to deep brain stimulation – to see if they influence the same step in
neuron development.
If these different treatments are all acting on the same step, that would
provide a precise target for development of new therapies, Enikolopov says,
and potential therapies could be screened more quickly.
But if different therapies target different steps in neurogenesis, that
could make different treatments appropriate under different conditions, he
suggests. For example, Parkinson's disease is associated with depression.
Doctors may be better off treating such patients with an antidepressant
drug that acts downstream of the step where Parkinson's attacks, in order
for the treatment to have an effect.
In either case, Enikolopov asks: "How is the generation of new neurons
translated into improved mood? That is the most critical and unanswered
question."
The team is also testing mice pups treated with Prozac to see if
neurogenesis responds the same way in juveniles as in adults. They hope
this may shed light on concerns over whether Prozac is appropriate to give
to children.
Journal reference: Proceedings of the National Academy of Sciences (DOI:
10.1073/pnas.0601992103)
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Weblinks
The Human Brain special report, New Scientist
http://www.newscientist.com/channel/being-human/brain
Grigori Enikolopov, Cold Spring Harbor
http://gradschool.cshl.edu/enikolo_.html
Proceedings of the National Academy of Sciences
http://www.pnas.org/
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