Pubdate: Thu, 29 Mar 2001 Source: San Jose Mercury News (CA) Copyright: 2001 San Jose Mercury News Contact: Website: .....Author: Lisa M. Krieger, Mercury News


The body produces its own marijuana-like chemical that may play a role in the creation of memories, according to a new research findings by UC-San Francisco scientists.

The study, reported in today's issue of the journal Nature, suggests that the molecule, known as a cannabinoid, may regulate the flow of messages along the pathway in the brain used to build a memory.

Although researchers determined nearly a decade ago that the brain contains a molecule that mimics the active ingredient in marijuana, its location and role in the brain has remained a puzzle.

The University of California-San Francisco study concludes that the molecule works within a part of the brain known as the hippocampus, a region associated with the learning process.

And while researchers do not yet know the exact mechanism of action, they believe that the molecule may block the normal inhibition of messages sent by brain cells -- in other words, it tells the gates of neural pathways to stay open, not shut.

Paradoxically, as any pot smoker knows, marijuana is hard on memory. That made cannabinoid even more interesting to the scientists.

``It seems to me that anything . . . conserved throughout evolution must be good for you,'' said Rachel Wilson, a graduate student in the laboratory of Roger Nicoll, professor of cellular and molecular pharmacology and physiology at UCSF.

The likely explanation, according to the UCSF team, is that marijuana confuses and disrupts the same cognitive system that the naturally occurring molecule supports. Perhaps it incites changes in the strength or pattern of the messages, the scientists suggest.

Normally, messages fly back and forth along pathways between neurons, many times a minute. One type of neuron triggers messages; the other shuts them down. Working together, they create a system where messages are routinely sent and discarded.

But every so often, the cannabinoid molecule is released by the trigger cell, sending a signal that a message is important and deserves repeating.

This may contribute to the creation of a new memory, according to the authors.

It may also influence the complex cascade of biochemical reactions that convert short-term memories into permanent ones.

Some scientists also think that cannabinoid disregulation -- when the body produces to much or too little of the molecule -- may be linked to mood disorders.

The goal of future research is to learn how this natural system works, and whether it can be exploited for therapeutic purposes.