.........




In 1972 brain researchers from Johns Hopkins University made a puzzling discovery that would illuminate scientists' understanding of drug addiction.

They found that the human brain's neurons had specific receptor sites for opiate drugs: opium, heroin, codeine and morphine. But then there was the obvious question.
Why would nature put in our brains a receptor for a plant? After all, humans beings didn't evolve over millions of years eating opium or shooting heroin.

The scientists reasoned there must be some other function for these receptors sites. They soon figured out that the active ingredient in all these opiates - morphine - had a chemical structure similar to endorphins, a class of chemicals present in the brain . Endorphins are feel-good chemicals naturally-manufactured in the brain when the body experiences pain or stress. They are called the natural opiates of the body.

Endorphins flood the space between nerve cells and usually inhibit neurons from firing, thus creating an analgesic effect. On a lower level they can excite neurons as well. When endorphins do their work, the organism feels good, high, or euphoric, and feels relief from pain [analgesia]. Logically, endorphin levels go up when a person exercises, goes into labor, or is stressed out. Although they seem to be triggered by stress, endorphins can do more than relieve pain, they actually make us feel good.

Like an evil twin, the morphine molecule locks onto the endorphin-receptor sites on nerve endings in the brain and begins the succession of events that leads to euphoria or analgesia. 

This imposter is more powerful than the body's own endorphins because the organism can actually control how much of the feel-good chemical hits the brain. Since we are all pleasure-seeking organisms, the motivation to self-administer such a drug is easy to understand.

The drawback, of course, is addiction.