GENTECH archive 8.96-97


Genetic control of behavior

			  Genetic control of behavior

UPn  09.10.96 23:31   

Copyright 1996 United Press International. All rights reserved.
The following news report may not be republished or redistributed, in whole or
in part, without the prior written consent of United Press International.
 UPI Science Writer
   SAN FRANCISCO, Oct. 9 (UPI) -- In a study that points to genetic control of
some aspects of behavior, scientists reported Wednesday they bred a genetically
engineered strain of mice lacking a protein that apparently plays a role in 
sensation, stress and aggressiveness.
   While the mice appeared normal on the outside, they had a lower pain
threshold and were more anxious, and the males tended to be more aggressive, 
investigators said in the British journal Nature.
   The altered mice could not produce pre-proenkephalin, the protein precursor
of enkephalin, the natural opiate thought to be involved in preventing pain and
controlling a variety of behaviors, said Andreas Zimmer of the National
Institute of Mental Health in Bethesda, Md.
   "The lower pain threshold in the study mice suggests that enkephalins are
indeed involved in pain modulation," Zimmer said in an interview.
"Interestingly, enkephalin-deficient mice display the normal analgesic response
to stress, suggesting that not every painful situation is cushioned by
   "We all produce opiate-like substances that are very important. Apparently,
they control our reaction to pain. The idea is well known," said Zimmer, citing
the examples of soldiers or accident victims feeling no immediate pain in the
initial shock of their injuries.
   "People think the body produces these opiates, and they prevent us from
feeling pain during the initial shock of trauma. What we have done is knock out
this gene in mice and look at the pain perception in these mice."
   The pain-sensitive mice, which also turn out to be quite easily irritated 
anxious, could prove useful tools in testing pain- relieving drugs, Zimmer 
   "The mice tell us the way we react to pain is determined by our genes. There
are people who react with great sensitivity, who can't tolerate pain and others
with a great tolerance. That is determined by our genes," he said.
   The study also indicates a genetic influence over the animal's feeling of
well-being, he said.
   "The deficient mice don't feel well; they're not happy," Zimmer said. "This
substance is apparently important to our reaction to pain and how we feel. This
isn't really surprising because we know opiates are consumed as drugs not
because the users want to reduce pain but because they want to boost that
feeling of well-being. These mice will help us analyze the neural pathway
   Investigators are studying the pain paths in humans, looking for human genes
that determine reactions to migraine headaches and other pain.
   "We want to look at which gene is responsible for determining how sensitive
we are to pain and whether they will determine our susceptibility to migraines
and other genetic disorders," Zimmer said.
   Programs are already underway to screen human populations for genes 
the susceptibility and sensitivity to pain, he said.

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