Date: Around 1993
The body produces a chemical when it is in pain. Can we detect
that chemical through a blood test and quantitatively determine how much pain
a person is experiencing?
Endorphines are hormones the body produces when in pain. They
function to "deaden" nerves, so that the pain will not seem as intense. They
are called the body's "opiates" because opium binds to the same receptor cites
as do endorphins. Your suggestion to qualitatively correlate pain with
endorphin production is intriguing. I can think of a few snags, though.
Endorphins are released in response to a variety of stimuli, not just pain.
For example, any stress, lack of sleep, excitement, depression, even intense
joy and laughter release endorphins. So, it is not solely a "pain chemical."
You would have to control all the other stimuli in order for your
quantification to have meaning. But there is some research into correlating
endorphin levels with certain human behavior. For instance, those prone to
developing substance (drug, alcohol, tobacco, etc.) addictions may have lower
than average endorphin producing capacities. If a correlation is found, a
potential method of treating these people may be found. Good thinking,
though! Who knows, maybe pain releases a special endorphin which can be
We know of a few neurochemicals involved in pain transmission.
Some of the specifics of exactly how they act are currently being
investigated. Most of this cannot be detected by a blood test for two
1) Since these are probably intrasynaptic neurotransmitters (they are in
between neural cells) they are present in very low concentrations and those
neurons do some reuptake of the neurotransmitter which further lowers their
concentration. Low concentration means difficulty in detecting them.
2) Most of these neurochemicals are located in the central nervous system (CNS
- includes brain and spinal chord). The CNS is tightly wrapped by a
biochemical barrier called the Blood-Brain Barrier. So not much of the
neurochemicals get into the bloodstream. One could get around this to some
degree by doing a spinal tap (putting a needle into the fluid that bathes the
CNS) but alas this is somewhat dangerous and is still indirect.
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Update: June 2012