Ask A Scientist© Biology Archive

Author:      deenaharper
Text:        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?

Response #:  1 of 2
Author:      wizkid
Text:        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 
quantified!

Response #:  2 of 2
Author:      psych
Text:        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 
reasons:

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.