Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers make surprise discovery that some neurons can transmit three signals at once

08.03.2005


Findings reported in Nature Neuroscience give new understanding to how cells in auditory system organize before hearing develops



Generations of neuroscientists have been indoctrinated into believing that our senses, thoughts, feelings and movements are orchestrated by a communication network of brain cells, or neurons, each responsible for relaying one specific chemical message called a neurotransmitter. Either neurons release a neurotransmitter that excites a neighboring cell, thereby triggering an electrical discharge and enhancing brain activity, or they dispatch a signal that quells a neuron’s activity. So, when researchers at the University of Pittsburgh discovered that immature rat brain cells could fire a simultaneous three-punch salvo – three neurotransmitters bursting out of a single cell -- it was a finding they knew would excite more than just neurons.

Just as surprising, they report in the lead article of this month’s Nature Neuroscience, is that by definition these three neurotransmitters are seemingly at odds with each other. One, glutamate, is a textbook excitatory neurotransmitter; while the other two, GABA and glycine, are quintessential inhibitory neurotransmitters.


Information is transmitted between neurons when one cell releases a neurotransmitter at a synapse, the point of contact between cells. When released from a cell, neurotransmitters are sent on a one-way ride that dead ends at the membrane of the adjacent cell. Like lock and key, they bind to specific receptors on the surface of the receiving cell, causing its electrical activity to be enhanced or inhibited.

The first week after birth marks a critical phase in the developing rat brain, a time period comparable to three months gestation in a human, when neurons are meticulously organizing and self-selecting to assemble into specific brain structures and neuronal networks. It has long been known that a specific receptor for glutamate, the NMDA receptor, plays a crucial role in these processes, but how inhibitory synapses, which account for about half of the brain’s cellular connections, would gain access to these receptors has long puzzled researchers. But now, the Pittsburgh researchers believe they have solved some of the mystery. During this crucial period, immature inhibitory synapses also release the excitatory neurotransmitter glutamate, and by mimicking excitatory synapses, can stimulate NMDA receptors.

"It first appeared odd to us that an immature inhibitory synapse would want to release an excitatory neurotransmitter. After all, this contradicts the most basic principles that have defined the field of neuroscience. But when we also found that this glutamate activates NMDA receptors at the most critical stage of brain development and organization, we realized that this could explain a number of fundamental questions," explained Karl Kandler, Ph.D., associate professor of neurobiology at the University of Pittsburgh School of Medicine, and the study’s senior author.

"These findings shed new light on how inhibitory synapses evolve and are assembled into functional circuits in the developing brain," he added.

Many brain disorders, like epilepsy, schizophrenia and depression, involve deficits that prevent normal inhibition of cells. Dr. Kandler’s research could eventually provide insight into the biological cause of these disorders and help to identify novel approaches for prevention and treatment. Further study could have particular implications for dyslexia and tinnitus – often referred to as ringing in the ears – which can be caused by abnormal inhibitory signaling within the auditory system, a region of the brain that is the focus of Dr. Kandler’s research.

Before there can be practical clinical applications several questions need to be answered, including how GABA, glycine and glutamate synapses cooperate to activate NMDA receptors. In the traditional sense, when inhibitory synapses are mature, they would never release glutamate, nor would they be able to depolarize a cell, both of which are required for NMDA receptor activation. But, as if by design, during the exact period when the auditory brain is undergoing refinement, the GABA and glycine neurotransmitters can produce depolarizations, a process that normally can only be achieved by excitatory transmitters.

It is not yet known how long the cells retain this unique capacity, for how long the neurons are able to release all three neurotransmitters or what causes the cells to stop releasing glutamate as they mature. But according to the study’s first author, Deda C. Gillepsie, Ph.D., a post-doctoral associate working with Dr. Kandler, things become more normalized within three weeks of birth, or about one week after hearing is fully developed. So, perhaps early auditory experience provides the signals that stop the cells from releasing glutamate, which is a prerequisite for correctly processing auditory information.

"It will be interesting to find out whether abnormal hearing, such as partial deafness or hearing dominated by noise, which in humans can affect normal language development, would cause glutamate to still be released. Finding such an association would be intriguing, but for now this remains just an hypothesis that will require much study, Dr. Gillespie said.

The third author of the study is Gunsoo Kim, Ph.D., who is now pursuing post-doctoral studies at the University of California, San Francisco.

Lisa Rossi | EurekAlert!
Further information:
http://www.upmc.edu

More articles from Life Sciences:

nachricht The dense vessel network regulates formation of thrombocytes in the bone marrow
25.07.2017 | Rudolf-Virchow-Zentrum für Experimentelle Biomedizin der Universität Würzburg

nachricht Fungi that evolved to eat wood offer new biomass conversion tool
25.07.2017 | University of Massachusetts at Amherst

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA mission surfs through waves in space to understand space weather

25.07.2017 | Physics and Astronomy

Strength of tectonic plates may explain shape of the Tibetan Plateau, study finds

25.07.2017 | Earth Sciences

The dense vessel network regulates formation of thrombocytes in the bone marrow

25.07.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>