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 Mantis shrimp vs. disco clams: Colorful sea creatures do more than dazzle
19.11.2019 | University of Colorado at Boulder

nachricht Deep-sea bacteria copy their neighbors' diet
19.11.2019 | Max-Planck-Institut für Marine Mikrobiologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Atoms don't like jumping rope

Nanooptical traps are a promising building block for quantum technologies. Austrian and German scientists have now removed an important obstacle to their practical use. They were able to show that a special form of mechanical vibration heats trapped particles in a very short time and knocks them out of the trap.

By controlling individual atoms, quantum properties can be investigated and made usable for technological applications. For about ten years, physicists have...

Im Focus: Images from NJIT's big bear solar observatory peel away layers of a stellar mystery

An international team of scientists, including three researchers from New Jersey Institute of Technology (NJIT), has shed new light on one of the central mysteries of solar physics: how energy from the Sun is transferred to the star's upper atmosphere, heating it to 1 million degrees Fahrenheit and higher in some regions, temperatures that are vastly hotter than the Sun's surface.

With new images from NJIT's Big Bear Solar Observatory (BBSO), the researchers have revealed in groundbreaking, granular detail what appears to be a likely...

Im Focus: New opportunities in additive manufacturing presented

Fraunhofer IFAM Dresden demonstrates manufacturing of copper components

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden has succeeded in using Selective Electron Beam Melting (SEBM) to...

Im Focus: New Pitt research finds carbon nanotubes show a love/hate relationship with water

Carbon nanotubes (CNTs) are valuable for a wide variety of applications. Made of graphene sheets rolled into tubes 10,000 times smaller than a human hair, CNTs have an exceptional strength-to-mass ratio and excellent thermal and electrical properties. These features make them ideal for a range of applications, including supercapacitors, interconnects, adhesives, particle trapping and structural color.

New research reveals even more potential for CNTs: as a coating, they can both repel and hold water in place, a useful property for applications like printing,...

Im Focus: Magnets for the second dimension

If you've ever tried to put several really strong, small cube magnets right next to each other on a magnetic board, you'll know that you just can't do it. What happens is that the magnets always arrange themselves in a column sticking out vertically from the magnetic board. Moreover, it's almost impossible to join several rows of these magnets together to form a flat surface. That's because magnets are dipolar. Equal poles repel each other, with the north pole of one magnet always attaching itself to the south pole of another and vice versa. This explains why they form a column with all the magnets aligned the same way.

Now, scientists at ETH Zurich have managed to create magnetic building blocks in the shape of cubes that - for the first time ever - can be joined together to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

High entropy alloys for hot turbines and tireless metal-forming presses

05.11.2019 | Event News

 
Latest News

The measurements of the expansion of the universe don't add up

19.11.2019 | Physics and Astronomy

Ayahuasca compound changes brainwaves to vivid 'waking-dream' state

19.11.2019 | Health and Medicine

Mantis shrimp vs. disco clams: Colorful sea creatures do more than dazzle

19.11.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>