Endorphins "Opiates" Within the Brain

More than three decades ago, reaseachers discovered that nerve cells in the brain have opiate receptors, to which opiates such as heroin and morphine attach themselves. The fit is so perfect between the opiates and the receptors that scientists reasoned there must be some natural substance in the brain that also fits these receptors. This led in 1975 to the discovery of enkephalins, a group of natural substances produced in the brain that seem similar to the drug morphine and do indeed fit the opiate receptors. Several of these substances have been given the name endorphins--a word coined to mean "morphine within"
It is hypothesized that endorphins play a role in our normal control of pain and in the production of pleasant emotional states. For example, it has long been known that stimulating parts of the brain can produce pleasure and control intractable pain. It is now believed that such stimulation acts on the brain to produce more endorphins. Acupuncture is also thought to stimulate nerve cells to produce endorphins. Endorphins may provide the answer to the puzzle of how people gain relief from placebo (inert) drugs. Provided they believe the drug is a potent painkiller, it appears that the individuals respond by producing more endorphins in the brain, which then release their pain-killing properties.
Researchers hypothesize that the body  stops producing its endorphins when external opiates are taken. Without an internal mechanism to deal with averse stated, the individual experiences painful withdrawal symptoms if the external opiate is withheld. Withdrawal may be produced by the lack of endogenous endorphins or may simply be more severe by their absence.
Recently scientists have discovered that the opiate receptor sites can be occupied by a substance that prevents opiates  and endorphins from attaching themselves to the receptors. One such opiate antagonist is naloxone, which is being used in experiments to treat addiction. When an individual takes naloxone, the opiate has no effect--it neither produces a rush nor reduces withdrawal symptoms. The hope is that the repeated experience of taking an opiate without any effect will eventuall break the addiction.