A drug that increases levels of a naturally occurring chemical may help marijuana users kick the habit, according to new research published this week (October 13) in Nature Neuroscience. In rats, the drug, called Ro 61-8048, boosted brain levels of kynurenic acid dosed with THC, marijuana’s active ingredient, which subsequently diminished dopamine-driven neural activity associated with pleasure. In monkeys, the same treatment reduced voluntary use of THC by 80 percent.
“The really interesting finding is that when we looked at behavior, simply increasing kynurenic acid levels totally blocked the abuse potential and the chance of relapse,” coauthor Robert Schwarcz, a neuroscientist at the University of Maryland, told Smithsonian.com. “It’s a totally new approach to affecting THC function.”
Though marijuana may not have serious long-term consequences, and may even hold potential in treating various medical maladies, it is commonly used as a recreational drug, and some people who abuse it show signs of addiction to the substance. This addiction is believed to stem from THC’s ability to activate the pleasure circuitry of the brain, increasing levels of dopamine and eliciting feelings of happiness. Kynurenic acid can also mediate dopamine-regulated brain activity, and was thus a top target of Schwarcz and his colleagues as they looked for ways to inhibit THC’s euphoric effects.
Indeed, dosing rats with Ro 61-8048 caused kynurenic acid levels to rise, after which THC no longer elicited the dopamine-driven brain activity in the reward centers of the brain, including the nucleus accumbens. It seemed that kynurenic acid was literally blocking the brain’s dopamine receptors, thereby decreasing the pleasurable feelings normally elicited by THC. As a result of the treatment, both rats and monkeys with the ability to self-dose with THC reduced their drug intake by about 80 percent.
“Currently, we’re doing some experiments with nicotine abuse, and there’s some very interesting preliminary data indicating it may work the same way,” Schwarcz told Smithsonian.com.