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 Chronic stress induces fatal organ dysfunctions via a new neural circuit
21.08.2017 | Hokkaido University

nachricht New malaria analysis method reveals disease severity in minutes
14.08.2017 | University of British Columbia

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Nagoya physicists resolve long-standing mystery of structure-less transition

21.08.2017 | Materials Sciences

Chronic stress induces fatal organ dysfunctions via a new neural circuit

21.08.2017 | Health and Medicine

Scientists from the MSU studied new liquid-crystalline photochrom

21.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>