Pubdate: Thu, 01 Aug 2002
Source: Seattle Times (WA)
Copyright: 2002 The Seattle Times Company
Contact:  http://www.seattletimes.com/
Details: http://www.mapinc.org/media/409
Author: Faye Flam, Knight Ridder Newspapers

STUDY: MARIJUANA EASES TRAUMATIC MEMORIES

PHILADELPHIA - Scientists have known for years that the brain makes 
substances almost identical to the active ingredient in marijuana, but the 
function of these "cannabinoids" remained mysterious. Researchers now say 
they help to extinguish traumatic memories.

"In certain situations, being able to forget is very important for 
emotional survival," said George Kunos, a neurobiologist at the National 
Institutes of Health.

The research, published today in the journal Nature, is not an endorsement 
for pot smoking, scientists said. Instead, the findings may help scientists 
develop new drugs to treat anxiety, post- traumatic-stress disorder and 
phobias.

"This paper is not saying you should go ahead and smoke marijuana," said 
Pankaj Sah, a neuroscientist at the Australian National University in 
Canberra who wrote an accompanying editorial in the journal. "It's saying 
that it's worth thinking about these specific actions of these compounds."

In the 1980s, scientists were surprised to find the brain has special 
receptors for the psychoactive elements in cannabis, Kunos said. An Israeli 
scientist named Rafael Mechoulam then found that the brain made its own 
versions of these cannabinoids.

To figure out why, authors of this latest study, from the Max Planck 
Institute of Psychiatry in Munich, Germany, decided to examine mice that 
had been engineered genetically so that they lacked cannabinoid receptors.

Neuroscientist Beat Lutz said he and his colleagues conditioned the mice to 
associate a mild shock with the sound of a bell. Normal mice eventually 
lost the association between the bell and the shock. "They figure out that 
the tone is not dangerous anymore and say, 'I don't have to freeze,' " Lutz 
said.

But the mice lacking the cannabinoid system never readjust, always freezing 
in terror at the sound.

Researchers also found that normal mice produce the natural cannabinoids 
when they are extinguishing their traumatic association with the bell.

It's not clear whether the cannabinoid system helps the mice to forget the 
traumatic association of the bell and the shock, or just gives them enough 
mental flexibility to adjust to a new situation, Lutz said. It's possible 
that the cannabinoids are important for the ability to relearn and readjust 
in a number of situations.

Kunos, from the National Institutes of Health, said that the cannabinoids 
probably play other roles. Using similar methods to Lutz, he found that 
they help regulate appetite.

Sah, of the Australian National University, said the latest findings may 
explain why some people with psychiatric problems try to find relief with 
marijuana. Although experts often have labeled marijuana use as a 
contributor to these people's mental illness, he suggested that people with 
certain psychiatric problems perhaps are self- medicating in an attempt to 
help their brains extinguish some painful or traumatic memory or thought.

Lester Grinspoon, a pro-marijuana psychiatrist at Harvard University and 
author of the 1971 book "Marijuana Reconsidered," said he would like to see 
cannabis made into pills that could be prescribed, but said the drug is not 
patentable and therefore would be unattractive for drug companies to 
manufacture and market.

Lutz suggested that, instead of supplying extra cannabinoids, a drug might 
enhance the effects of natural ones.

He also suggested such a drug might need to be taken in conjunction with 
psychotherapy, during which patients would work on getting rid of fearful 
associations.

"Just smoking marijuana all day won't help," he said.
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MAP posted-by: Beth