Both groups of scientists found not just one pain-suppressing chemical in the brain, but a whole family of such proteins. The Aberdeen investigators called the smaller members of the family enkephalins (meaning "in the head"). In time, the larger proteins were isolated and called endorphins, meaning the "morphine within." The term endorphins is now often used to describe the group as a whole.

The discovery of the endorphins lent weight to the general concept of the gate theory. Endorphins released from brain nerve cells might inhibit spinal cord pain cells through pathways descending from the brain to the spinal cord. Endorphins might also be activated when you rub or scratch your itching skin or aching joints. Laboratory experiments subsequently confirmed that painful stimulation led to the release of endorphins from nerve cells. Some of these chemicals then turned up in cerebrospinal fluid, the liquid that circulates in the spinal cord and brain. Laced with endorphins, the fluid could bring a soothing balm to quiet nerve cells.

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