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Clumps of protein in the brain, called beta-amyloid plaques, are the primary marker of Alzheimer’s disease. For long, scientists knew that these clumps interfered with memory signals in the brain — but they weren’t sure how.
Now a team from Stanford University School of Medicine has traced the effects of beta-amyloid plaque to activity of the brain’s endogenous cannabinoids, or endocannabinoids. These compounds are produced naturally by the brain and mimic the effects of compounds in cannabis. Among many functions, cannabinoids play a key role in memory and learning.
“Endocannabinoids in the brain are very transient” Looking at brain slices taken from rats, the researchers observed that clumps of beta-amyloid indirectly impaired memory pathways by interfering with the normal activity of cannabinoids.
This interference with the brain’s cannabinoids may be the mechanism by which early memory deficits in Alzheimer’s are formed, says Daniel Madison, PhD, who led the study. Cannabinoids may also present a new opportunity for treating Alzheimer’s before the disease advances, he adds.
The findings were published June 18 in the journal Neuron.
However, Dr. Madison says it would be inaccurate to assume that smoking cannabis could counteract the effects of beta-amyloid plaque on memory and learning.
“Endocannabinoids in the brain are very transient and act only when important inputs come in,” explains Dr. Madison. Marijuana’s main ingredient, THC, has a much longer-lasting effect, he notes.
“Exposure to marijuana over minutes or hours is different: more like enhancing everything indiscriminately, so you lose the filtering effect. It’s like listening to five radio stations at once.”
On the other hand, a 2013 study by researchers from Neuroscience Research Australia suggests an ingredient in marijuana called CBD could be beneficial. The team, led by Tim Karl, PhD, found that treatment with CBD led to drastic improvements in memory in mice genetically engineered to mimic Alzheimer’s disease.
Besides the potential to combat Alzheimer’s symptoms, some studies suggest cannabinoids also hold promise in slowing progression of the disorder.