STUDY SHOWS HOW BRAIN BLOCKS PAIN

Body Found To Produce Marijuana-Like Compound

Wounded soldiers and badly injured athletes often report they don't feel
pain for hours after being hurt, and now researchers are beginning to
understand why - it's because the brain produces its own natural marijuana.

Scientists already knew that pot can reduce some kinds of pain, and that
the brain actually produces marijuana-like chemicals called cannabinoids.

But now a team led by a University of Georgia researcher has found that
those pot-like substances are crucial in blocking pain in the process
called "stress-induced analgesia," according to a study published Wednesday
in the journal Nature.

"The reason marijuana produces its effects is because the active
ingredient, Delta-9 THC, acts on the same receptors as the brain's natural
cannabinoids," said Andrea Hohmann, a researcher in UGA's psychology
department and the lead author of the paper.

Their discoveries could mean an eventual end to the debate over whether
medical uses of marijuana should be legal: The researchers hope to develop
a prescription drug that will boost the body's own marijuana-like
chemicals, but one without unwanted side effects - one that won't get you high.

Several states allow doctors to prescribe marijuana for patients with
cancer, AIDS or other illnesses, though it's forbidden by federal law.

Pot is not only an effective pain reliever for them, but also suppresses
nausea and increases appetite. Nausea and loss of appetite are frequent,
unwanted side effects of "opiate" pain-killers like morphine, which act
through a different mechanism than the cannabinoids and can have toxic side
effects marijuana doesn't, Hohmann said.

New drugs wouldn't exactly be pot in a pill, though, but a medicine that
would increase the brain's own natural pot-like chemicals, Hohmann said.

Scientists have known about these brain-produced cannabinoids for years,
but the new research gets scientists much closer to understanding how they
work inside the brain, Hohmann said.

"On a very basic level we have a new understanding of brain control of
neural functions. We know that we can basically tweak the levels of the
brain's own cannabinoid-like substances," she said.

The research started five years ago with a summer research project in
Hohmann's lab by an undergraduate UGA honors student, Mark Neely. Other
contributors include students Richard Suplita and Nathan Bolton, UGA
psychology faculty members Philip Holmes and Jonathon Crystal and
collaborators at the University of California-Irvine, Brown University and
two Italian universities, the University of Urbino Carlo Bo and the
University of Parma.

Their first step was to show that blocking brain receptors the cannabinoid
chemicals act upon also reduced the brain-induced analgesia.

To measure the effect, experimenters shocked rats' feet with an electric
current, then timed how quickly the rats flicked their tails away from a
heated metal plate. The procedure does not injure the rats but mimics the
same stress-induced analgesia seen in humans and animals following serious
injuries, Hohmann said.

Since that first experiment, Hohmann and her fellow researchers have
identified ways to use synthetic chemicals to increase cannabinoid levels
in lab rats' brains. They have also gotten a better understanding of where
the effect occurs in the brain.

One of the cannabinoid-enhancing chemicals, discovered by a team led by
University of California-Irvine researcher Daniele Piomelli, is the most
likely candidate to develop into a prescription drug.

It's possible a drug also would be effective against stress-related
disorders such as post-traumatic stress syndrome, Hohmann said.

The discovery is, in a way, similar to earlier finds that animal brains
naturally produce chemicals similar to morphine and other opiate
pain-killers, she said.

"This is the first time we have data that indicate that the brain's 2AG
(one of the pot-like chemicals) suppresses pain. That could have tremendous
clinical importance and may lead to new ways to treat pain and stress,"
Hohmann said.