Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Alzheimer’s: Cellular Mechanism Provides Explanation Model for Declining Memory Performance

21.09.2016

Loss of neuronal contacts impairs nerve cells that control activity of the hippocampus

Alzheimer’s disease triggers memory and learning disorders. To date, the causes are poorly understood. Now, researchers of the German Center for Neurodegenerative Diseases (DZNE) are shedding light on a possible mechanism: As Martin Fuhrmann and co-workers describe in the journal “Neuron,” loss of neuronal contacts that release the neurotransmitter acetylcholine impairs the function of specific nerve cells.


This microscopy image depicts the neuronal network of the hippocampus including O-LM interneurons (red and yellow) and other cell types. The current study shows that interneuron dysfunction may contribute to learning deficits associated with Alzheimer’s disease. Source: DZNE / Julia Steffen

The affected “interneurons” regulate activity of the hippocampus, which is considered to be the brain’s memory control center. The results of this study may pave the way for a more effective treatment of memory disorders associated with Alzheimer’s.

Brain cells are interlinked with each other into a freeway for nerve impulses. For this network to work properly, different types of cells have to harmonize to fulfill their tasks. For instance, while some brain cells pass on signals in a way that triggers firing of downstream cells, others slow down signal transmission. “Usually, there is a fine-tuned balance between excitation and inhibition.

It is presumed that this interplay is disturbed by Alzheimer’s,” explains DZNE researcher Dr. Martin Fuhrmann. “This may cause nerve cells to become hyperactive, which leads to discharges that resemble epileptic conditions. In Alzheimer’s disease, the hippocampus is among the first brain areas to be affected and the region where learning and memory processes occur.”

Inhibitory Cells Under the Microscope

Consequently, the Bonn-based neurobiologist and his team colleagues investigated a specific class of neurons that are referred to as “O-LM interneurons”. They act upon other hippocampal neurons and thereby restrain their activity. This effect is called “inhibition.”

To date, little was known on the role these interneurons play in Alzheimer’s disease. Hence, the researcher trained mice – healthy specimen and others who displayed typical symptoms of Alzheimer’s – to recognize a certain environment. Moreover, Fuhrmann and his colleagues used microscopy techniques to track how the interneurons adapted to the learning task.

Usually, during learning existing connections between neurons are modified and new ones created. Indeed, the researchers observed such changes happening at the interneurons of the healthy mice. However, in the rodents that exhibited symptoms of Alzheimer’s, cellular wiring was disturbed and connections were not established in some cases. Besides, these mice had problems to recognize their training environment.

What caused the faulty wiring? The researchers found out that this effect was triggered by the loss of a specific set of cellular connections that normally reach out to the interneurons. “Already in the early stages of Alzheimer’s cholinergic projections degenerate. Their name derives from the fact that they release a neurotransmitter called ‘acetylcholine’,” Fuhrmann says.

“Some of these connections usually link up to the interneurons we investigated. When they get lost this has direct impact on the interneurons. Their cellular wiring becomes dysfunctional, which impairs their ability to inhibit others cells.”

Study Results Support the “Cholinergic Hypothesis”

It has long been suspected that memory decline associated with Alzheimer’s may be caused by the loss of cholinergic projections. Reduction of these cellular contacts leads to a deficiency of acetylcholine. Hence, one treatment approach is to counteract the shortage of the neurotransmitter through medication, which turned out to be not successful on the long-term. However, the current work elucidates how acetylcholine might be related to memory function on the cellular level.

“Our study now points to a mechanism that may be relevant for humans. The loss of cholinergic connections impairs the regulating ability of hippocampal interneurons. This worsens memory performance,” Fuhrmann explains. “Looking ahead, these findings could help to develop drugs to treat memory problems caused by Alzheimer’s more effectively than it is possible today.”

Original publication
Dysfunction of somatostatin positive interneurons associated with memory deficits in an Alzheimer’s disease model.
Lena C. Schmid, Manuel Mittag, Stefanie Poll, Julia Steffen, Jens Wagner, Hans-Rüdiger Geis, Inna Schwarz, Boris Schmidt, Martin K. Schwarz, Stefan Remy und Martin Fuhrmann.
Neuron, DOI: 10.1016/j.neuron.2016.08.034

Contact
Dr. Marcus Neitzert
DZNE, Communications
+49 (0) 228 / 43302-271
marcus.neitzert(at)dzne.de

Dr. Marcus Neitzert | idw - Informationsdienst Wissenschaft
Further information:
http://www.dzne.de/en/about-us/public-relations/meldungen/2016/press-release-no-12.html

Further reports about: Alzheimer’s Cellular DZNE Neuron acetylcholine cholinergic nerve cells neurons

More articles from Health and Medicine:

nachricht One gene closer to regenerative therapy for muscular disorders
01.06.2017 | Cincinnati Children's Hospital Medical Center

nachricht The gut microbiota plays a key role in treatment with classic diabetes medication
01.06.2017 | University of Gothenburg

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>