The active ingredient in marijuana -- tetrahydrocannabinoid or THC -- interferes with synchronized activity between neurons in the hippocampus of rats, according to a paper to be published in the December 2006 issue of Nature Neuroscience. The authors suggest that this may explain why the drug impairs memory.
György Buzsaki and colleagues recorded from multiple neurons in the hippocampus -- a brain region known to be important for memory -- of rats. Normally neurons in this region form groups that fire action potentials, or nerve impulses, together at about 4-10 times per second. But when the authors injected THC, or a related synthetic drug, into the hippocampus, this synchrony was disrupted. The drugs did not change the total number of action potentials produced, just their tendency to occur at the same time. Animals with less synchronized neural activity under the drug performed less well in a standard test of memory, suggesting that synchronized neural firing is important for normal hippocampal function.
György Buzsaki (Rutgers University, New Brunswick, NJ, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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