Marijuana may contain compounds that slow the memory loss associated with Alzheimer's disease.
Credit: U.S. Fish and Wildlife Service
SYDNEY: Marijuana may contain compounds that slow the memory loss associated with Alzheimer's disease, according to a new U.S. study.
Marijuana has strong anti-inflammatory effects, and many researchers believe that there is a compelling link between chronic inflammation and the progression of Alzheimer's, said co-author Gary Wenk, a professor of psychology at Ohio State University.
"Inflammation in the brain is part of aging," Wenk said. "It happens to almost all of us as we age. But in some cases, this inflammation gets out of hand and causes serious damage."
In the study, treatment of rats with a synthetic compound similar to marijuana reduced inflammation in older animals, in addition to making them "smarter," said Wenk, who presented the results at the Society for Neuroscience meeting in Atlanta yesterday.
"The compound substantially improved the memories of the older rats," he said. "These animals were able to hold on to key details of a specific task. Untreated older rats, on the other hand, were not."
Evidence suggests that people who regularly smoked marijuana in the 1960s and 1970s rarely develop Alzheimer's disease, said Wenk, adding that researchers are eager to develop a drug with the anti-inflammatory properties of marijuana, but without the drug's psychoactive effects.
The researchers treated young and old rats with WIN-55212-2 (WIN), a synthetic drug similar to marijuana. While the compound improved memory and helped to control inflammation, it is not a candidate for use in humans because it still contains substances that could trigger a high.
"We don't use marijuana in our experiments because we're trying to find a compound that isn't psychoactive," Wenk said. "And using synthetic compounds may eventually help us to separate the beneficial effects from the psychoactive effects."
In the study, the rats were treated with lipopolysaccharide (LPS), a substance that triggers an immune response that mimics the inflammation found in Alzheimer's patients. Some of the rats were also treated with WIN each day for the three-week duration of the study.
During the third week of treatment, the animals were subjected to a memory test. They navigated a water maze that required finding an escape platform hidden just below the surface of opaque water. The rats were given several opportunities over three days to acclimate to the water maze. On the fourth day, the researchers timed how quickly each rat found the platform.
"The maze task is sensitive to memory impairment and also to ageing," Wenk said. "Old rats tend to be pretty bad at navigating the maze. It's kind of like an elderly person trying to find his way around a house that he's not familiar with."
Once the testing was complete, the researchers began to examine the animals' brains for signs of inflammation - they looked for certain kinds of immune cells that are typically found in large quantities in the brains of former Alzheimer's patients.
They found that the marijuana-like compound decreased inflammation in the brains of young and old rats, and that the treated animals in both age groups could find the platform in the water faster than the non-treated animals. The most marked difference was between the treated and non-treated older rats.
"The compound significantly improved the older rats' memories," Wenk said. "They found the platform faster, suggesting that they were less apt to forget key information for this task. It's a pretty good prediction of how a human would respond to this drug."
For a full feature on the positive and negative effects of marijuana, see Cosmos, Issue 10, p.66.
with Ohio State University
