Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brain cells seen recycling rapidly to speed communications

12.06.2003


The tiny spheres inside brain cells that ferry chemical messengers into the synapse make their rounds much more expeditiously than once assumed, National Institute of Mental Health (NIMH) - funded researchers have discovered. They used a dye to track the behavior of such synaptic vesicles in real time, in rat brain cells. Rather than fusing completely with the cell membrane and disgorging their dye contents all at once, brain vesicles more often remained intact, secreting only part of the tracer cargo in each of several repeated, fleeting contacts with the membrane, report Richard Tsien, D.Phil., Stanford University, and colleagues Alex Aravanis and Jason Pyle, in the June 5, 2003 Nature. Dubbed "kiss-and-run" recycling, this allows for more efficient communication between brain cells, suggest the researchers.

Brain cells communicate in a process that begins with an electrical signal and ends with a neurotransmitter binding to a receptor on the receiving neuron. It lasts less than a thousandth of a second, and is repeated billions of times daily in each of the human brain’s 100 billion neurons. Much of the action is happening inside the secreting cell. There, electrical impulses propel vesicles into the cell wall to spray the neurotransmitter into the synapse. Likened to soap bubbles merging, or bubbles bursting at the surface of boiling water, this process of membrane fusion (*RealPlayer format) may hold clues about what goes wrong in disorders of thinking, learning and memory, including schizophrenia and other mental illnesses thought to involve disturbances in neuronal communication.

Neurons must recycle a finite number of vesicles. In "classical" membrane fusion, the vesicle totally collapses and mixes with the cell membrane, requiring a complex and time-consuming and retrieval and recycling process. Yet, Tsien and colleagues point out that this process was discovered in huge neurons, such as those in squid giant synapses, with tens or hundreds of thousands of vesicles per nerve terminal. By contrast, they find that the comparatively tiny nerve terminals of the mammalian brain must make do with only about 30 functional vesicles – hardly enough to keep up with the split-second demands of synaptic communication if vesicles can only be replenished via the, one-shot classical process, they argue. Hence, the "kiss-and-run" hypothesis.



To observe single vesicles in action, Tsien and colleagues put a fluorescent dye into nerve terminals in cultured neurons from the rat hippocampus, a key memory hub involved in learning. The dye was later washed out of neuronal membranes, but it remained trapped in the vesicles, enabling the researchers to take snapshots of their activity at synapses following electrical stimulation, using a microscope, pulses of fluorescent light, and a CCD imaging device.

When they tracked single vesicles following stimulation, they usually observed a series of abrupt and lasting -- albeit partial -- decreases in fluorescence, indicating multiple fusion events. Yet, only rarely was there a full loss of fluorescence, indicating full classical collapse.

"A likely explanation is that most fusion events were simply too brief to permit dye to escape completely," noted Tsien and colleagues. "After rapid retrieval by a process that maintained vesicle integrity, vesicles remained available for repeated fusion, supporting their repeated re-use for neurotransmitter release. Vesicles are readily refilled with neurotransmitter so each fusion can send a meaningful signal. Together, brief fusion, rapid retrieval and re-use would enable small nerve terminals of the central nervous system to get full mileage from their limited set of vesicles."

Only at times of "all-out vesicular mobilization" would most of the hippocampal neuron vesicles likely shift to the classical mode of membrane fusion, they concluded.

Another study published in the same issue of Nature by Dr. Charles Stevens, The Salk Institute, and colleagues, also found evidence in support of "kiss-and-run."


NIMH is part of the National Institutes of Health (NIH), the Federal Government’s primary agency for biomedical and behavioral research. NIH is a component of the U.S. Department of Health and Human Services.

Video Archive: "Calcium Channels and Local and Long Distance Signaling on Both Sides of the Synapse," Richard Tsien, D.Phil., Stanford University, NIH Neuroscience Seminar Series, Dec. 10, 2001. http://www.nimh.nih.gov/videos/tsien.cfm.




Jules Asher | EurekAlert!
Further information:
http://www.nimh.nih.gov/videos/tsien.cfm
http://www.nimh.nih.gov/

More articles from Life Sciences:

nachricht Synthetic nanoparticles achieve the complexity of protein molecules
24.01.2017 | Carnegie Mellon University

nachricht Immune Defense Without Collateral Damage
24.01.2017 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Arctic melt ponds form when meltwater clogs ice pores

24.01.2017 | Earth Sciences

Synthetic nanoparticles achieve the complexity of protein molecules

24.01.2017 | Life Sciences

PPPL physicist uncovers clues to mechanism behind magnetic reconnection

24.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>