Whenever we do get interventions that supposedly deliver neurogenesis we can use this to objectively verify that neurogenesis has actually occurred. But I bet our neurogenesis researchers won't do that unless our great stroke association follows up with the researchers.
http://www.alphagalileo.org/ViewItem.aspx?ItemId=166744&CultureCode=en
Scientists from the RIKEN Center for Life Science Technology (CLST)
in Japan have used a new non-invasive PET scanning technique to obtain
images of neuron proliferation in the subventricular zone and
subgranular zone of the hippocampal dentate gyrus. Neurogenesis in the
hippocampal dentate gyrus is known to be particularly affected by
depression.
These two areas are known to be neurogenic regions,
where neural stem cells give rise to new neurons throughout our lives.
Hippocampal neurogenesis is known to be associated with depression and
the effect of antidepressive medication, but it is also involved in
learning and memory, so scientists are keen to find techniques that can
monitor cell proliferation in the region. However, the process of
neurogenesis is very hard to monitor non-invasively. It is possible
using magnetic resonance imaging, but with MRI the tracers do not move
into the brain effectively and must be injected directly into the brain
fluid, making is invasive and difficult to perform.
Positron emission tomography (PET) is another method
that has been used. Previously, attempts have been made to use a
molecule called [18F]FLT as a marker for cell proliferation in the brain
in PET, but unfortunately the difference in signal strength between
regions with and without cell growth was small. “We were not exactly
sure why this was happening,” says Tamura, “but surmised that it is
because the body actively pumps the molecule out of the brain through
the blood-brain barrier, using active transport mechanisms. This means
that it is difficult for [18F]FLT to accumulate in the brain in
sufficient concentrations to allow effective imaging.”
To test whether this was the case, they tried injecting
rats with a drug called probenecid, which is known to inhibit the
active transport of molecules like [18F]FLT outside of the brain. They
were happy to see that the strategy worked. They found clear signals of
neurogenesis in the two areas of the adult brain, and these signals were
significantly decreased in the hippocampal dentate gyrus of rats that
had been treated with corticosterone to trigger depression. When the
rats were treated with an anti-depressive selective serotonin reuptake
inhibitor, the amount of cell proliferation was shown to increase,
demonstrating that the drugs were countering the loss of neurogenesis
caused by the corticosterone.
According to Yosky Kataoka, who led the research team,
“This is a very interesting finding, because it has been a longtime
dream to find a non-invasive test that can give objective evidence of
depression and simultaneously show whether drugs are working in a given
patient. We have shown that it is possible, at least in experimental
animals, to use PET to show the presence of depression and the
effectiveness of drugs. Since it is known that these same brain regions
are involved in depression in the human brain, we would like to try this
technique in the clinic and see whether it turns out to be effective in
humans as well.”
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