Researchers have discovered a correlation between the number of neurons that produce orexin—a chemical messenger important for sleep and appetite—and addiction, according to a new study with cocaine-addicted rats.
Restoring the number of orexin neurons to normal, or blocking orexin signaling in the brain, made the rats no longer addicted, suggesting the increased orexin neurons is an essential change in the brain that causes the addicted state. The findings identify a promising avenue for treating addiction with orexin-based therapies.
As reported in Biological Psychiatry , rats given intermittent cocaine demonstrated behaviors observed in human users, including increased motivation to acquire the drug (even when they received a painful shock), depression- and anxiety-like behaviors, and relapse after several months of abstinence.
Researchers also found that mimicking the typical binge-like pattern of drug use—with access to cocaine on-and-off throughout the day—produced a model that reflected addiction in humans better than the “gold standard” of continuous access.
“Remarkably, these ‘addicted’ rats had a greater number of brain cells that produce the neuropeptide orexin,” says Morgan James, a postdoctoral research fellow at the Rutgers University Brain Health Institute.
The increased number of neurons was persistent, lasting for at least six months after cocaine use, which might explain why addicts often relapse following long periods of abstinence.
“The addicted brain appears to become more dependent upon this increased number of orexin neurons,” notes senior author Gary Aston-Jones, director of the Brain Health Institute. “Lower doses of an orexin blocker were effective at decreasing addiction behaviors in these rats than in those with shorter access to cocaine and that were less addicted.”
Source: Rutgers University