BRAIN COMPOUNDS MIMIC MARIJUANA
Substances help sort out memory information, neuroscientists suggest.
By David Brown
The Washington Post
 A substance similar to the main ingredient of marijuana is highly active in 
the part of the brain that sifts incoming information in memory and 
immediately forgetting the rest, according to a research published Thursday ( 
Aug 21, 1997 ).
        The new finding, described in the journal Nature, sheds some light on 
the largely mysterious process of memory formation. Indirectly at least, it 
also helps explain some of the effects of heavy marijuana use.
 Researchers know that the brain possesses two substances that behave like 
the active ingredients in marijuana - a family of compounds known as 
cannabinoids.
 One substance called anandamide, was isolated in 1992 and found to be widely 
distributed throughout the brain. The second, called 2-AG was discovered in 
1995 in the intestine and was, according to first reports, absent from the 
brain.
 In the new report, Nephi Schweitzer, Daniele Piomelli and Paul Schweitzer 
analyzed rat brains for 2-AG. They found the brains were loaded with it. In 
fact, it was present in amounts 170 times greater then anandamide, suggesting 
that 2-AG is the more important compound, at least as far as behavior is 
concerned.
 The researchers used slices of living brain tissue to study the function of 
2-AG in the hippocampus, a region that temporarily stores information before 
it is either committed to memory or forgotten.
 A key mechanism in that winnowing process appears to be a phenomenon called 
"long-term potentiation" (LTP). With LTP, a cell changes its electrical 
sensitivity for long periods - days or weeks - in response to a certain 
pattern of initial stimulation.  It is a way for the brain to select out - in 
real time - a few bits of data from the mass of stimulation it contacts every 
waking moment.
 The California team found that 2-AG blocked LTP in certain nerve pathways in 
the hippocampus. This suggests that 2-AG may be essential for the act of 
forgetting - an act that is important in the highly selective process of 
creating memories.
 "Some of the stimuli are selected and memorized and others are just 
forgotten," said Piomelli.
 Neuroscientists believe the information carried by the hippocampus cells 
experiencing long-term potentiation is ultimately sent to another region, 
where it's stored permanently as memory.
 2-AG's ability to block long-term potentiation - and with it, presumably, 
memory formation - help explain some of marijuana's effects, Piomelli 
believes. Specifically, he thinks it sheds light on the common observations 
that heavy or 
frequent pot-smoking impairs short-term memory. 
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