Weeding out painful memories

Researchers at the Max Planck Institute of Psychiatry in Germany, together with colleagues from Italy, were able to locate receptors in the brain that are critical in helping us manage our fears.

They took two sets of mice—one group genetically engineered to lack cannabinoid receptors, and a group of regular mice (a "control" group)—and first conditioned them to expect a shock whenever they heard a certain sound. During the following days, the mice were repeatedly exposed to the sound. At first, all mice were frightened by the sound. But as the days went on the control mice quickly stopped being scared by the sound, while the genetically engineered mice "could hardly forget it."

Cannabinoids are the chemicals that bind to the cannabinoid receptors, and they include a neurotransmitter, anandamide, that is found naturally in the brain, as well as tetrahydrocannabinol (THC), the active component in marijuana. But as far as overcoming our fears or aiding in aversive memory clearance, smoking marijuana is not likely to be as effective since it affects our brains and bodies in many other ways.

However, scientist do hope that this research leads to drugs that can help with stress disorders, anxiety and phobias, without the other side effects of marijuana.