Natural 'marijuana' in brain eases anxiety

DURHAM, N.C., June 13 (UPI) -- U.S. researchers said they found a way to calm the fears of anxious mice with a drug that alters their brain chemistry.

Ahmad Hariri, a neurobiologist at the Duke University's Institute for Genome Sciences & Policy, and colleagues at the National Institutes of Health found human genetic differences related to the same brain chemistry influence how well people cope with fear and stress.

"What is most compelling is our ability to translate first from mice to human neurobiology and then all the way out to human behavior," Hariri said in a statement. "That kind of translation is going to define the future of psychiatry and neuroscience."

The common thread of their research is a gene encoding an enzyme called fatty acid amide hydrolase, which breaks down a natural endocannabinoid chemical in the brain that acts in essentially the same way as marijuana -- hence the name endocannabinoid.

In the new study, Andrew Holmes' group at the National Institute on Alcoholism and Alcohol Abuse tested the effects of a drug that blocks fatty acid amide hydrolase activity in fear-prone mice that had also been trained to be fearful through experiences in which they were delivered foot shocks. The drug allowed a faster recovery from fear thanks to higher brain endocannabinoid levels.

Hariri showed human study participants a series of pictures depicting threatening faces, while their brains were being scanned. People with the fatty acid amide hydrolase gene associated with lower enzyme function and higher endocannabinoid levels showed a greater decrease in activity suggesting those individuals may be better able to control and regulate their fear response, Hariri said.

The findings were published in Molecular Psychiatry.