Narrator: This is Science Today. In the past decade, scientists have discovered two receptors in the brain which are affected by synthetic drugs called cannibinoids. These drugs mimic the active ingredient found in marijuana. Ian Meng, a researcher at the University of California, San Francisco, likens the relationship between these brain receptors and cannibinoids, to a lock and key.

Meng: The receptors are on the cell membrane and they're sort of like the lock and the cannibinoid, or the synthetic drugs we now have in the laboratory, can fit into that lock like they key and unleash all of its actions.

Narrator: Meng discovered these actions include a process similar to the release of natural endorphins which results in pain reduction.

Meng: And what we have now found is that the cannabinoids do the same thing. They can tap into this same brain circuitry and activate a very specific population of neurons to reduce the pain signal - just like the natural endorphins do.

Narrator: For Science Today, I'm Larissa Branin.