Nearly a decade ago, researchers determined that the brain contains a molecule that mimics the active ingredient in marijuana, but its location and role in the brain were unclear. Now, UCSF researchers have discovered that the molecule acts, at least in part, in a region of the brain that plays a key role in learning and memory.
The study, reported in the March 29 issue of Nature, suggests, the researchers say, that the molecule, known as a cannabinoid, plays a role in particular cognitive functions within a structure known as the hippocampus. Paradoxically, marijuana disrupts cognitive function and the likely explanation, the researchers say, is that marijuana disrupts the very cognitive system the cannabinoid normally supports.
The circumstances under which cannabinoid might act are unknown, but one possibility is that it contributes to the formation of new memories, says the lead author of the study, Rachel I. Wilson, a graduate student in the laboratory of Roger A. Nicoll, PhD, UCSF professor of cellular and molecular pharmacology and physiology and a member of the Keck Center for Integrative Neuroscience at UCSF.
Another possibility is that cannabinoid enables neurons to shift from one behavioral state to another. "We know that when the brain is carrying out different behaviors - whether directing the body to a desired destination or sleeping - it has different patterns of synchronous rhythms. Cannabinoid might enable neurons to shift from one behavioral state to another," she says.
In either case, she says, the cannabinoid system would be supporting cognitive processes. While merely speculative at this point, the hypothesis is reasonable, says Wilson, as the cell receptor through which cannabinoid acts has been conserved through evolution, suggesting the cannabinoid molecule is beneficial to many species.
"It seems to me than anything expressed so heavily and conserved throughout evolution must be goo
Contact: Jennifer O'Brien
University of California - San Francisco