Taste, temperature and pain sensations are neurologically linked
Date:
March 21, 2022
Source:
University of Oklahoma
Summary:
Biologists have found that the brain categorizes taste, temperature
and pain-related sensations in a common region of the brain and
that the brain also groups these sensations together as either
pleasant or aversive, potentially offering new insights into how
scientists might better understand the body's response to and
treatment of pain.
FULL STORY ==========================================================================
If you have eaten a chili pepper, you have likely felt how your body
reacts to the spicy hot sensation. New research published by biologists
at the University of Oklahoma shows that the brain categorizes taste, temperature and pain- related sensations in a common region of the
brain. The researchers suggest the brain also groups these sensations
together as either pleasant or aversive, potentially offering new insights
into how scientists might better understand the body's response to and treatment of pain.
==========================================================================
"The spicy hot sensation you get from a chili pepper is actually a
pain sensation...this follows activation of pain-related fibers that
innervate the tongue and are heat sensitive," said Christian H. Lemon,
Ph.D., an associate professor in the Department of Biology in the Dodge
Family College of Arts and Sciences at OU. "What happens is a chemical
in chili peppers, called capsaicin, causes activation of pain fibers
and 'tricks' the neurons to react like there is a heat stimulus in your
mouth, so you'll notice when you eat spicy foods, your body will react
to try to remove the heat - your blood vessels can dilate and you can
start to sweat because your body 'thinks' it's overheating." Lemon,
who is also a member of the OU Institute for Biomedical Engineering,
Science and Technology, and researchers in his lab, Jinrong Li, Ph.D.,
and?Md Sams Sazzad Ali, Ph.D., published an article in The Journal
of Neuroscience that examines how taste, temperature and pain-related sensations interact in the brain. Their article was also selected for
the journal's Featured Research section.
"Neural messages associated with pain are partly carried by neural
circuits involved with sensing temperature," Lemon said. "This would
explain, for example, why when you touch a hot stove, it's a burning
pain. There are intimate ties between temperature and pain, and there
are intimate ties between temperature and taste...just about everything
we eat is either warmed or cooled, and that's known to have a fairly
robust effect on the way we perceive certain tastes." The research
team wanted to better understand how temperature and pain intersect
with taste neurologically. Building on their previous research that had
shown that temperature and taste signals come together in a particular
section of the midbrain, Lemon's research group used mouse models under anesthesia to artificially stimulate temperature and pain-related fibers, combined with a physiological method to monitor the actions occurring
in the brain to determine the connection between these senses.
"It's been known that temperature and taste can activate some of the
same cells in the brain, but this was rarely systematically studied,"
he said. "We wanted to know if the temperature responses that we were
seeing in this part of the brain were actually attributable to activation
of thermal and pain-related fibers that innervate the head, face and
mouth. To do this we used a modern genetic technology where we could
insert a protein into these 'temperature/ pain' cells that allowed us to control these cells with blue light -- we could turn the cells on with
a light, like a light switch." "What we found is that these neurons
that scientists have studied for a long time as taste neurons actually
respond to artificial stimulation of these temperature/pain cells," he
added. "This is significant because most scientists that have looked at
taste, they're usually only studying neural circuits from the perspective
of taste. Pain scientists are usually only looking at pain- related
responses, but they actually come together in this part of the midbrain,
and not only do they come together, they do so in a very systematic way
where preferred tastes and preferred temperatures are separated from
adverse taste and temperatures in terms of the way that the responses
are happening in this part of the brain." The researchers categorize
preferred or pleasurable tastes as something sweet, like sugar, whereas
adverse tastes are bitter -- which can signify that something may be toxic
or harmful. Similarly, people, and mice, have preferred temperatures,
like a comfortably warmed or cooled environment as compared to an extreme
cold or extreme heat stimulus.
Through this artificial stimulation of temperature/pain cells
and the corresponding taste neurons, they discovered the brain
segregated preferable tastes and temperatures from adverse tastes and temperatures. This finding offers new insights into how these senses
interact, which could have implications for how scientists understand
the brain's responses to stimuli that cause pain.
"What our results show is that in a midbrain circuit there's a very
orderly representation of taste and temperature hedonics -- whether
or not something is pleasurable or aversive -- dependent on input from
these temperature/pain cells," Lemon said. "These findings suggest that
the brain is actually using common cells to represent information from different senses where there are relationships between the senses. Since
pain has ties to temperature sensing, these results might provide clues
as to how temperature or pain signals might interact with other senses,
which could be important for developing novel therapeutic strategies
for pain management."
========================================================================== Story Source: Materials provided by University_of_Oklahoma. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Jinrong Li, Md Sams Sazzad Ali, Christian H. Lemon. TRPV1-Lineage
Somatosensory Fibers Communicate with Taste Neurons in the Mouse
Parabrachial Nucleus. The Journal of Neuroscience, 2022; 42 (9):
1719 DOI: 10.1523/JNEUROSCI.0927-21.2021 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220321115901.htm
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