A compound derived from marijuana might one day help fight the memory loss associated with Alzheimer's disease, a new study suggests.
Researchers have shown that a synthetic drug similar to cannabis can help older rats perform better on a spatial memory task.
Over a period of three weeks, Gary Wenk at Ohio State University in Columbus, US, and colleagues injected the brains of young and old rats with an inflammatory molecule that created an immune response in the animals' brains which mimics that seen in Alzheimer's patients.
During the same period the researchers also injected some of the rats with a synthetic drug similar to cannabis, called WIN-55212-2, which stimulates the brain receptors that normally respond to cannabis compounds.
The team then tested the rats by having the animals navigate through a water maze. Because rodents dislike water they will do their best to find the dry platform hidden in the maze.
"The maze task is sensitive to memory impairment and also to ageing," Wenk says. "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." Researchers gave the animals three days to learn the maze and then timed them on the fourth day.
The rats that received WIN-55212-2 in both age groups found the platform faster than their control counterparts. However, the difference between the treated and untreated animals' performance was greatest among the older rats. The brains of rats receiving the synthetic drug also showed less sign of inflammation.
The results are impressive particularly because of the low dose of drug used in the experiment, comments Ken Mackie at the University of Washington in Seattle, US, who was not involved in the study.
"They gave them a relatively low dose, even for a rat." Mackie says that this aspect of the study makes the prospect of developing a similar treatment for humans with Alzheimer's disease "more promising".
Wenk cautions, however, that WIN-55212-2 still causes psychoactive effects similar to cannabis, and as such is not yet a candidate for human use. Researchers are currently trying to develop a similar drug that could control inflammation in the brain without a concomitant high.
Wenk presented the findings today at the annual Society for Neuroscience meeting in Atlanta, Georgia, US.
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