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Aerosols: the future of the spliff?
From New Scientist, 21 February 1998
Marijuana Special Report:
From pain relief to stimulating the appetites of
patients on chemotherapy, marijuana seems to have
plenty going for it as a medicine. But many doctors
worry about the weed's effects on lungs, and some
would rather it didn't get people quite so stoned. For
them, the dream solution would be some kind of
aerosol or smokeless cigarette filled with a
redesigned version of the drug that doesn't bend
minds.
The first part of the dream is already being worked
on -- the second will be harder to achieve.
For years, doctors have been allowed to prescribe a
swallowable capsule containing the main active
ingredient of cannabis,
delta-9-tetrahydrocannabinnol (THC). The problem
is that patients complain of side-effects such as
anxiety and say they prefer to smoke grass because
that way they can control the dose through careful
inhaling. Some esearchers think they can improve
matters by developing an aerosol form of THC.
Even if it works, though, the spray would still make
people high, and changing that won't be easy. The
problem is cannabis's peculiar pharmacology. In the
past decade, researchers have discovered that all
cannabis's main effects -- from changes in pain
perception to euphoria and the munchies -- are the
work of a single type of receptor, copies of which
protrude from neurons scattered far and wide in the
brain. This is a problem because normally
researchers fine-tune the effects of drugs by
tailoring them to home in like a smart bomb on a
small subset of the receptors they usually stimulate.
For cannabis and THC, there is no subset. The
targets are all identical.
One solution might be to develop drugs that bypass
these identical surface receptors and mimic chemical
changes triggered by cannabis deeper in cells. But
this is a long way off. In the meantime, there is a
more basic puzzle to solve: why the brain has
cannabis receptors in the first place.
A few years ago, researchers discovered a
cannabis-like substance in the brain called
anandamide (after the Sanskrit for "bliss"). Like
THC, anandamide stimulates cannabis receptors to
dampen the electrical activity of neurons and reduce
the flow of neurotransmitters across synapses. But
nobody has a clear idea why. The best guess is that
the brain uses anandamide as a central fine-tuner
of electrical activity.
Copyright New Scientist, RBI Limited 1998
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