ALZHEIMER鈥檚 disease and other neurodegenerative disorders could soon be
treated with nose drops. Researchers in Minnesota say that the nasal passage
holds great promise as a conduit for delivering drugs into the brain, as the
olfactory system provides a direct link between the brain and the outside
world.
Getting drugs into the brain is one of neuroscience鈥檚 challenges. The
molecules of many drugs are too large to cross the blood-brain barrier, the
tightly woven cells in the blood vessels in and around the brain that form a
kind of protective fence guarding brain tissue. Nerve growth factor, a promising
treatment for Alzheimer鈥檚 disease, is one such drug. Injecting NGF does not
work, and procedures such as grafting NGF-producing cells directly into the
brain are expensive and risky.
But William Frey, a neuroscientist at the Alzheimer鈥檚 Research Center at the
Regions Hospital in St Paul, woke one morning with the idea of using nose drops
to carry NGF to the brains of his patients. 鈥淚 knew that bad things could get in
this way,鈥� he says. 鈥淚t occurred to me that maybe good things could get in this
way too.鈥�
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Olfactory nerves are unusual in that they run straight from the olfactory
bulb in the brain to the nasal cavity, where they come into contact with
鈥渙dorants鈥� in the air. But occasionally, Frey points out, the odd anatomy of the
olfactory system can be dangerous because it provides a way for some viruses,
such as herpes, to sneak into the brain. In one study, even tiny gold particles
sprayed into the noses of monkeys were traced along the olfactory nerves and
into the animals鈥� brains.
So Frey and his colleagues decided to see if NGF could be delivered in nose
drops. After anaesthetising 12 rats, the researchers gave half the animals drops
in their noses over 30 minutes and injected the rest with NGF. They found that
within an hour, a significant amount of NGF had made its way not only into the
olfactory bulb, but also into the hippocampus, amygdala and other regions not
directly involved in smelling. In contrast, very little of the NGF injected into
the other rats reached the brain. The same results held true when the
researchers administered insulin growth factor 1, a possible treatment for
stroke, in nose drops.
Frey鈥檚 team will report on its findings at a meeting of the American
Association of Pharmaceutical 快猫短视频s in San Francisco in November. The nose,
they say, could deliver drugs not only for Alzheimer鈥檚 disease but for a range
of other neurodegenerative conditions as well, including Parkinson鈥檚 disease and
multiple sclerosis. The team has a patent on the idea and is working with a
biotechnology company to develop it.