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 Nerves control the body’s bacterial community
26.09.2017 | Christian-Albrechts-Universität zu Kiel

nachricht Ageless ears? Elderly barn owls do not become hard of hearing
26.09.2017 | Carl von Ossietzky-Universität Oldenburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The fastest light-driven current source

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

Graphene is up to the job

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Nerves control the body’s bacterial community

26.09.2017 | Life Sciences

Four elements make 2-D optical platform

26.09.2017 | Physics and Astronomy

Goodbye, login. Hello, heart scan

26.09.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>