Behavior: Better Living Through Biochemistry

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As promising as this research has been, Government agencies did not open the funding spigot for it until the 1970s, when the return of many drug-addicted veterans of Viet Nam prompted concern about just how such opiates as heroin and morphine work. The payoff came quickly. In 1973 three groups of researchers, Solomon Snyder and Candace Pert of Johns Hopkins University, Eric Simon of New York University and Lars Terenius of Uppsala, Sweden, announced almost simultaneously the discovery of specific receptors for such opiates in the brain. Snyder's lab located a high density of receptors in the medial thalamus, an area of the brain responsible for registering deep sustained pain; in the amygdala, a region of the brain's limbic system that plays a role in controlling emotion; and in the spinal cord.

But scientists wondered why the body developed opiate receptors in the first place, unless it somehow produces its own internal narcotics. Acting on just such a premise, Pharmacologists John Hughes and Hans Kosterlitz at Scotland's University of Aberdeen in 1975 isolated two peptides from the brains of pigs. Remarkably, the peptides seemed to be natural opiates. Hormonologist Choh Hao Li of the University of California in San Francisco had already discovered similar molecules in the pituitary glands of camels, animals whose insensitivity to pain had long intrigued scientists. Hughes and Kosterlitz dubbed the molecules enkephalins (from the Greek word for head). Subsequently, scientists identified kindred painkilling molecules that they called endorphins (meaning "the morphine within").

Researchers are convinced that such chemicals may explain many behavioral mysteries. During World War II, Army medics were astonished by some soldiers who had lost limbs yet did not complain of pain; scientists now believe that these wounded men produced extra endorphins to dull the agony. Similar chemical magic may explain how Indian fakirs walk over hot coals and how acupuncture and placebos work.

The mind chemicals also hold promise for controlling emotional pain. Because the emotion-controlling amygdala region of the brain is rich in enkephalin receptors, scientists speculate that the molecules may act as a defense against disappointments and trauma. At the Salk Institute, Floyd Bloom is studying the possibility that endorphins may be involved in the pleasure received from alcohol and opiates. Once a person begins taking heroin, say, the natural production of endorphins may decrease. Thus, if addicts try to go cold turkey, the agony of withdrawal is severe. If scientists can create nonaddictive chemicals that bind, like the opiates—and work at Yale with clonidine suggests that they can—to the appropriate receptors, they may be able to ease pain of all kinds, including that connected with stopping a heroin habit.