Researchers know dendritic spines play a vital role. These tiny membranous structures protrude from dendrites’ branches; spread across the entire dendritic tree, the spines on one neuron collect signals from an average of 1,000 others. But more than a century after they were discovered, their function still remains only partially understood.
A Northwestern University researcher, working in collaboration with scientists at the Howard Hughes Medical Institute (HHMI) Janelia Farm Research Campus, has recently added an important piece of the puzzle of how neurons “talk” to one another. The researchers have demonstrated that spines serve as electrical compartments in the neuron, isolating and amplifying electrical signals received at the synapses, the sites at which neurons connect to one another.
The key to this discovery is the result of innovative experiments at the Janelia Farm Research Campus and computer simulations performed at Northwestern University that can measure electrical responses on spines throughout the dendrites.
A paper about the findings, “Synaptic Amplification by Dendritic Spines Enhances Input Cooperatively,” was published November 22 in the journal Nature.
“This research conclusively shows that dendritic spines respond to and process synaptic inputs not just chemically, but also electrically,” said William Kath, professor of engineering sciences and applied mathematics at Northwestern’s McCormick School of Engineering, professor of neurobiology at the Weinberg College of Arts and Sciences, and one of the paper’s authors.
Dendritic spines come in a variety of shapes, but typically consist of a bulbous spine head at the end of a thin tube, or neck. Each spine head contains one or more synapses and is located in very close proximity to an axon coming from another neuron.
Scientists have gained insight into the chemical properties of dendritic spines: receptors on their surface are known to respond to a number of neurotransmitters, such as glutamate and glycine, released by other neurons. But because of the spines’ incredibly small size — roughly 1/100 the diameter of a human hair — their electrical properties have been harder to study
In this study, researchers at the HHMI Janelia Farm Research Campus used three experimental techniques to assess the electrical properties of dendritic spines in rats’ hippocampi, a part of the brain that plays an important role in memory and spatial navigation. First, the researchers used two miniature electrodes to administer current and measure its voltage response at different sites throughout the dendrites.
They also used a technique called “glutamate uncaging,” a process that involves releasing glutamate, an excitatory neurotransmitter, to evoke electrical responses from specific synapses, as if the synapse had just received a signal from a neighboring neuron. A third process utilized a calcium-sensitive dye — calcium is a chemical indicator of a synaptic event — injected into the neuron to provide an optical representation of voltage changes within the spine.
At Northwestern, researchers used computational models of real neurons — reconstructed from the same type of rat neurons — to build a 3D representation of the neuron with accurate information about each dendrites’ placement, diameter, and electrical properties. The computer simulations, in concert with the experiments, indicated that spines’ electrical resistance is consistent throughout the dendrites, regardless of where on the dendritic tree they are located.
While much research is still needed to gain a full understanding of the brain, knowledge about spines’ electrical processing could lead to advances in the treatment of diseases like Alzheimer’s and Huntington’s diseases.
“The brain is much more complicated than any computer we’ve ever built, and understanding how it works could lead to advances not just in medicine, but in areas we haven’t considered yet,” Kath said. “We could learn how to process information in ways we can only guess at now.”
Other authors of the paper, all of HHMI Janelia Farm Research Campus, include lead author Mark T. Harnett, Judit K. Makara, Nelson Spruston (formerly of Northwestern University), and Jeffrey C. Magee, the senior author on the paper.
Megan Fellman | Source: EurekAlert!
Further information: www.northwestern.edu
More articles from Life Sciences:
Molecular snapshot of the plant immune system’s signal box
11.12.2013 | Max Planck Institute for Plant Breeding Research, Köln
Successful Teamwork: Unusual fungal metabolites with antitumor activity discovered by crowdsourcing
11.12.2013 | Angewandte Chemie International Edition
The molecular architecture of three key proteins and their complexes reveals how plants fine-tune their immune response to pathogens
Plants rarely get sick in their natural environment. When the threat of infection arises, a quick decision is made about the necessary countermeasures. The course is set by a protein which forms complexes with its partner proteins for this purpose.
Jane Parker from the Max Planck Institute for Plant Breeding ...
Researchers studying speciation of butterfly orchids on the Azores have been startled to discover that the answer to a long-debated question "Do the islands support one species or two species?" is actually "three species".
Hochstetter's Butterfly-orchid, newly recognized following application of a battery of scientific techniques and reveling in a complex taxonomic history worthy of Sherlock Holmes, is arguably Europe's rarest orchid species. Under threat in its mountain-top retreat, the orchid urgently requires conservation recognition.
A lavishly illustrated publication, titled "Systematic revision of Platanthera in ...
Researchers from Brown University and the University of Hawaii have found some mineralogical surprises in the Moon's largest impact crater.
Data from the Moon Mineralogy Mapper that flew aboard India's Chandrayaan-1 lunar orbiter shows a diverse mineralogy in the subsurface of the giant South Pole Aitken basin.
The differing mineral signatures could be reflective of the minerals dredged up at the time of the giant impact 4 billion years ago, ...
In power electronics systems bonded connections create the central electrical connections between adjoining surfaces.
The quality of these bonded connections is one of the main factors that determines the reliability and availability of drive systems in electric vehicles, and hence constitutes a major design challenge for German auto manufacturers aiming to electrify their vehicles.
Now the partners participating in the RoBE (Robust Bonds in ...
International team of scientists develops new feedback method for optimizing the laser pulse shapes used in the control of chemical reactions
In many ways, traditional chemical synthesis is similar to cooking. To alter the final product, you can change the ingredients or their ratio, change the method of mixing ingredients, or change the temperature or pressure of the environment of the ingredients.
Like an accomplished chef, chemists have become very skilled ...
11.12.2013 | Information Technology
11.12.2013 | Life Sciences
11.12.2013 | Agricultural and Forestry Science
11.12.2013 | Event News
10.12.2013 | Event News
05.12.2013 | Event News