Marijuana and Heroin Advance Understanding of Brain Chemistry

DRUG USE, DRUG ABUSE March 1993

Two recent, and almost simultaneous breakthroughs related to the way in which the primary active components of marijuana and opiate drugs affect the brain are pushing the frontiers of neuroscience (Kathy Fackelmann, "Marijuana and the Brain: Scientists Discover the Brain's Own THC," Science News, 2/6/93, Vol. 143 No. 6, p. 88; Marcia Barinaga, "Pot, Heroin Unlock New Areas for Neuroscience," Science, 12/18/92, Vol. 258, p. 1882; p. 1946; p. 1952).

In the 1970s, scientists discovered opioid receptors in the brain, and endogenous brain chemicals, known as enkephalins and endorphins, that bound to those brain receptors. But until late last year, they had been unable to clone the opioid-receptor gene. The story with tetrahydrocannabinol (THC), the primary psychoactive constituent of marijuana, was reversed. Two years ago, scientists succeeded in cloning the THC receptor, but late last year, a scientific team identified the endogenous brain chemical that bound to the THC receptor, anandamide.

The simultaneous discoveries have neuroscientists excited about the prospects for further understanding of brain mechanisms that affect pain, stress response, sleep, and memory. Two groups of researchers appear to have simultaneously cloned the long-sought oipiod receptor gene. A third group independently discovered the THC analogue, which they dubbed anandamide, from the Sanskrit for inner bliss.