Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brainstem blocks pain to protect key behaviors

08.11.2005


Certain behaviors, such as eating, drinking and urinating, are so crucial to survival that the brains of all vertebrates contain clusters of nerve cells that can suppress pain long enough to allow the animal to eat, drink -- or pee -- in peace.



A report from researchers at the University of Chicago, published early online in the Proceedings of the National Academy of Sciences, shows that by activating "OFF" cells and shutting down "ON" cells in the ventromedial medulla (VMM) – a small region in the brain stem – animals provide themselves with a form of "eating-induced analgesia," allowing them to complete essential tasks even in a difficult situation.

"Escaping pain and potential dangers may be important protective behaviors, but eating, drinking, and eliminating wastes are absolutely essential," said study author Peggy Mason, Ph.D., professor in the department of neurobiology, pharmacology and physiology (NPP) at the University of Chicago. "What we found was a very effective system that lets these animals focus on the essentials and postpone concerns that are slightly less pressing. It’s as if they could give themselves a six-second dose of morphine, allowing hunger to override pain."


Mason and colleague Hayley Foo, research associate in NPP, studied adult male rats in containers with a wire mesh floor that enabled them to deliver radiant heat to one hind paw. The heat caused no damage but was annoying enough to make the animal withdraw that paw within seconds.

When the rats ate, however, they postponed retracting the heated paw for six to eight seconds and continued to eat.

Food choice made no difference. Rats focused just as intently on standard rat chow as when munching chocolate chips, yogurt drops or butter cookies.

Although earlier studies found that eating took precedence over pain in food-deprived animals, this is the first study to show that feeding suppressed pain in well-fed animals.

To understand the neural basis of this form of pain suppression, the researchers next inserted electrodes to monitor brain activity in feeding rats.

The suspected source of pain relief was a cluster of cells in the VMM. In 1979, Howard Fields of the University of California at San Francisco identified two groups of neurons in the brain stem that could enhance or inhibit pain. Neurons that "facilitate" pain, which he labeled "ON cells, fire in bursts when animals are awake and are inactive during slow-wave sleep. "OFF" cells, which suppress pain, are active during slow-wave sleep.

Foo and Mason, who completed her post-doctoral training in Fields’ laboratory, found that the pain-enhancing ON cells were inhibited and the pain-suppressing OFF cells were excited during feeding, results that duplicated the effects of morphine. The changes occurred only during selected portions of eating, while the animal was both holding and chewing the food. A similar response took place when the animals drank water or urinated.

This response "protects critical behaviors from disruption," the authors note, "allowing an animal to nourish itself without being distracted." (Animals that don’t urinate are at high-risk for infections.)

As a final test the authors used drugs to inactivate the VMM. This completely eliminated the delayed response to pain.

"This is the best evidence so far on the biological significance of OFF cell activity," said UCSF’s Fields, who was not connected with the study. "It is a major step in understanding the neurobiological mechanisms of decision making in the face of conflict -- in this case the choice between whether to feed or flee. Off cells help you feed instead of flee."

Mason and Foo also found, however, that in situations that might be more dangerous, the feed-or-flee balance could be tipped the other way. Given just before feeding, a strong puff of air – perhaps indicating a nearby predator -- activated ON cells, and restored pain sensation. Such "predation-related stimuli," the authors speculate, "activate ON cells and thereby evoke a state of vigilant eating without concurrent sensory suppression."

"We have known for a long time that these cells could be manipulated by opioids, such as morphine," said Mason, "but we had no good explanation of what their natural role might be." Their prime location -- in the brain stem, the "Gold Coast of neuroanatomical property" -- suggests that they "must do something crucial." This study indicates that they "protect against distraction. They give precedence to essential behaviors."

Defects in this system could be linked to various disorders, Mason suggests, such as sudden infant death syndrome. Overactive OFF cells during sleep could mask the discomfort of oxygen deprivation.

Fields suspects that the link between eating and pain relief, in a society where the risks of caloric plenty far exceeds those of predation, may even be related to obesity. "Are OFF cells promoting bravery," he asked, "or gluttony?"

John Easton | EurekAlert!
Further information:
http://www.uchospitals.edu

More articles from Health and Medicine:

nachricht NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures
17.11.2017 | National Institute of Standards and Technology (NIST)

nachricht High speed video recording precisely measures blood cell velocity
15.11.2017 | ITMO University

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>