By ROBERT LEE HOTZ
Los Angeles Times

NEW ORLEANS Adding new fuel to the controversy over medical uses of
marijuana, researchers reported Sunday that active chemicals found in the
plant could serve as an effective remedy for the millions who suffer
serious pain each year, without the unwanted side effects of more
traditional morphinelike drugs.

New animal studies by research groups at the University of California, San
Francisco, the University of Michigan and Brown University showed that a
group of potent chemicals known as cannabinoids, which include the active
ingredient in marijuana, relieve several kinds of pain, including the kind
of inflammation associated with arthritis, as well as more severe forms of
chronic pain.

The scientists said they believe the new research opens the way for a new
class of drugs to control pain.

Marijuana's painkilling properties have long been an unheralded and
unconfirmed staple of medical folklore, but now, sophisticated animal
studies of the active biochemicals in marijuana, presented Sunday in New
Orleans at a meeting of the Society for Neuroscience, for the first time
demonstrated that they have a direct effect on pain signals in the central
nervous system and other tissues.

Unlike the current crop of painkillers based on opiates, the new class of
chemicals is not addictive, nor does it appear to carry the risk that
patients may develop tolerance for it and require increasing doses, the new
animal research indicated.

"Cannabinoids, at least in animal models, can reduce pain," said UCSF
pharmacology expert Ian Meng, who is studying the painkilling properties of
several synthetic cannabinoids.

To discover how these substances regulate pain, researchers traced the
tortuous biochemical pathway that pain signals follow from the site of an
injury, through the spinal cord, to the brain. In their experiments, they
used both the active ingredient in marijuana a chemical called delta9
THC and an array of more powerful synthetic creations.

Scientists discovered that molecular receptors to which the chemicals can
bind are so widely present that researchers at the Medical College of
Virginia now suspect that naturally occurring cannabinoids may govern the
body's basic threshold of pain.

Marijuana is the newest of nature's analgesic compounds to attract
scientific attention. From aspirin and willow bark, to opium and poppy
flowers, most modern painkillers are derived originally from plants.

Indeed, people have been writing about the painkilling properties of
marijuana since the 1830s, and a century ago, patent medicines based on
cannabis compounds were a staple of pharmacy shelves. As stringent drug
control laws were adopted at the turn of the century, the folk remedies
were abandoned.

Working in animals, Kenneth Hargreaves at the University of Texas reported
Sunday that the marijuanalike chemical can relieve the inflammation
associated with arthritis when injected directly at the site of an injury.
And Donald Simone at the University of Minnesota reported that the
chemicals also can block the onset of an extreme sensitivity to pain called
hyperalgesia, which flares up during nerve diseases and spinal cord injuries.

"These results suggest that local administration of the cannabinoid to the
site of injury may be able to both prevent pain from occurring and reduce
pain which has already occurred without producing side effects," Hargreaves
said.

A number of neuroscientists said Sunday that marijuana's newly confirmed
utility as a painkiller would inevitably broaden the drug's appeal beyond
those seriously ill patients who seek it out today in order to stimulate
appetites destroyed by wasting diseases such as AIDS or to alleviate the
nausea of chemotherapy.

"People who have serious illnesses will take the steps they feel they have
to take; certainly the new research you are hearing about here would lead
people in that direction," Walker said.

That, in turn, may spur broader federal support for research into
marijuana's analgesic effects, scientists said Sunday.