Several years ago, molecular biologists identified the elusive brain receptor where THC, the active ingredient in marijuana, did its work. Shortly after that discovery, researchers at Hebrew University in Jerusalem identified the body’s own form of THC, which sticks to the same receptors, in pulverized pig brains. They christened the internally manufactured substance “anandamide,” after the Sanskrit ananda, or bliss.

Anandamide has a streamlined three-dimensional structure that THC mimics, and both molecules slipped easily across the blood-brain barrier. Anandamide is a short-lived, fragile molecule, and does not produce a dramatic natural high, unlike a surge of endorphins, or dopamine—or the THC in a joint. In 2001, researchers at the Keck Center for Integrative Neuroscience at the University of California-San Francisco found evidence that THC may perform a signaling function in neurons containing GABA and glutamate. It appears that marijuana increases dopamine and serotonin levels through the intermediary activation of opiate and GABA receptors.

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