Behavior: Better Living Through Biochemistry

Although drugs have been used for decades to fight mental illness, scientists have not really understood how they worked. Now all that is changing. A miraculous pharmacopoeia is being explored to deal with every kind of ailment in the mind and body. Not too far off may be tailor-made drugs that will lull insomniacs into peaceful sleep, dull the throbbing of pain, organize a schizophrenic's thoughts and perhaps even simulate the pleasures of sex.

This revolution has been gradually brewing. Until they discovered in the 1930s that the disease pellagra was caused simply by a deficiency of B-complex vitamins, doctors thought that it was a form of psychosis. But proof that body and psyche are really part and parcel of the same physiological system did not come until the discovery of the first tranquilizers in the early 1950s. It was drugs like Thorazine that rapidly emptied mental hospitals, reducing a population of 560,000 to fewer than 200,000 in barely a generation.

Still, discoveries almost amounted to biochemical wizardry. Why, for instance, did drugs control disordered thought and hallucinations in some schizophrenics, yet fail abysmally in others? To unravel such puzzles, researchers turned increasingly to the brain, composed of tens of billions of nerve cells called neurons. Passing electrical impulses from one part of the brain to another, these elongated, finger-like cells communicate with one another across junctions or gaps—synapses—by the release of chemicals called neurotransmitters. As these chemical broad jumpers leap across a synapse, carrying their message, they attach themselves to the neighboring cell, triggering a fresh electrical charge in the adjoining neuron.

So far, scientists, have found at least 20 neurotransmitters. Each of these chemicals has a unique molecular configuration. As a result, neurotransmitters and any of the chemicals that mimic them—work like keys in a lock. They can only fit into those sites, or receptors, on the nerves that are specifically designed to accept them.

The intricacies of this system are just beginning to be unraveled. Scientists speculate that when the body produces too few or too many such chemicals, behavioral problems ensue. Severe depression, for instance, could be linked to abnormally low levels of a family of neurotransmitters called monoamines (serotonin, noradrenaline and dopamine), which can be destroyed by an enzyme called monoamine oxidase (MAO). To keep the enzyme from doing its work, chemists have developed drugs called MAO inhibitors. Other antidepressants, the tricyclics, increase the life of monoamines in the synapse.

Similarly, scientists have found that a low level of the neurotransmitter serotonin may be linked to insomnia. Researchers have been experimenting with tryptophan, the chemical from which the body makes serotonin. Only a small dose of tryptophan—which is found in many foods, notably milk—seems to ease the insomniac to sleep.