The psychoactive ingredient in marijuana that produces the "high" sought by users has been shown to reverse memory problems in aging mice. Researchers, who've been looking for ways to slow the effects of brain aging, hope it could have the same effect in older humans.
German and Israeli researchers showed that the memories of aging mice became nearly as sharp as those of young, two-month-old rodents when the older animals were given low doses of the marijuana compound known as THC.
"Old animals remembered as well, learned almost as well, recognized almost as well as young ones," said neuroscientist Andras Bilkei-Gorzo of the University of Bonn. He is lead author of the study of THC's effect on memory, published in the journal Nature Medicine.
Mice, which have a life expectancy of two years, have significant difficulty remembering and learning new things by the time they're one year old.
Bilkei-Gorzo and his team administered low doses of THC to mice at two months, 12 months and 18 months of age.
After stopping the drug for periods ranging from seven days to one month, they put the rodents through a series of experiments testing their memories. Researchers wanted to see whether the rodents recognized mice they had been exposed to previously, and if they could find their way out of a small pool of water.
The older mice that received a placebo had trouble remembering previous objects and scenarios despite repeated exposures. The adult mice treated with THC performed nearly as well as young rodents.
THC imitates the effect of cannabinoids produced naturally in the body, which fulfill important functions in the brain. But with age, the cannabinoid system deteriorates, resulting in cognitive declines. The marijuana ingredient, says Bilkei-Gorzo, rejuvenates the system.
Interestingly, he says, THC seemed to worsen the cognitive abilities of young mice because it over-activated their normal brain circuits. The effect is probably similar to marijuana's high in young people.
"The treatment made the young brain old and the old brain young," he said. "So that was something that was above our imagination."
Researchers hope to begin human trials of low doses of THC this year.
If it is shown to help the memories of aging adults, Bilkei-Gorzo says the psychoactive ingredient could be taken in the form of an herbal tea.