The compound is a synthetic cannabinoid, made in a lab to resemble marijuana.
Old rats given the compound performed better in a maze, according to research by Gary Wenk, PhD, professor of psychology and neuroscience at Ohio State University, and others.
What about people? "Now, I don't know, because I'm just a rat guy, whether this is going to work that well in humans," Wenk tells WebMD. "But it looks like it will, because of what we've seen with other drugs in other diseases."
The marijuana-like drug "won't cure the disease, but what it might do is stop the processes that are involved in making the disease worsen," Wenk says. "I think that's the most exciting aspect."
"What may matter is that we can tell people that we might be able to step in, stop the inflammation, and they might die of old age before the inflammation has a chance to rebuild itself, which we believe takes many decades," Wenk says.
"That's the main hope, I think," he says.
Reducing Brain Inflammation
Wenk's team tested the synthetic cannabinoid to curb brain inflammation in rats.
"Now inflammation in all these conditions doesn't cause the disorder," he says. But, "it has consequences."
"In fact, the inflammation appears long before plaques and tangles and memory impairment," Wenk says, referring to the plaques and tangles seen in the brains of people who die with Alzheimer's disease.
For their study, researchers looked at young and old male rats.
Some of the rats got the cannabinoid drug; others got a drug-free placebo. The rats received the drug or placebo through shots or a pump hooked up to their bodies.
Results showed less brain inflammation with the drug than with the placebo.
Plus, older rats taking the drug outperformed their placebo peers on a memory test involving a watery maze.
"Now, we didn't make them as smart as young rats. Nothing does that yet," Wenk says. "But we lessened the impairment by half."
"We've tested the animals' memory ability in a task that's vulnerable to, and then given them a drug to see if it could reduce their inflammation," Wenk says. "And we cut it down by 50% to 90%, depending on what part of the brain you look at."
"I'm not recommending that [people] go out and smoke marijuana," Wenk says.
"We have to produce this anti-inflammatory effect at a dose that doesn't make our rats high or impaired," he says. "This is a psychoactive compound and it is regulated for that reason."
"Now, I don't know what it means to be high if you're a rat, but I do know if you are high, you probably are memory-impaired; your attention is impaired," Wenk says.
Why This Drug?
"Anti-inflammatories in plants and antioxidants are a dime a dozen," Wenk says. "They're just everywhere."
"The important thing, though, is that they not have too many side effects and that they actually get in the brain.
"So that's what makes a ... drug like a cannabinoid so useful," he explains.
"It [this compound] does something that no other anti-inflammatory that I've tested in our model has ever done, and that's that it reduces inflammation in an old brain," Wenk says. "Old brains are different than young brains."
The drug hasn't been tested against Alzheimer's in people.
But if the research pans out, people might one day take such drugs to head off Alzheimer's decades later, Wenk notes.
"The problem is, who would take it?" he says. "We don't have reliable early tests [for Alzheimer's] -- not yet."
"So do we have to treat everyone? Well, that ends up being very expensive. We don't have an answer to that question yet," Wenk says.
Much more work lies ahead, but Wenk sounds hopeful.
"This is something that might actually happen in my lifetime, before I get to the point where I have to worry about it," Wenk says. "So from that standpoint, I think it's very positive."