The dark matter of the brain
Electrical synapses - omnipresent and yet hardly explored
Date:
April 5, 2022
Source:
Max-Planck-Gesellschaft
Summary:
They are part of the brain of almost every animal species, yet
they remain usually invisible even under the electron microscope.
FULL STORY ==========================================================================
They are part of the brain of almost every animal species, yet they remain usually invisible even under the electron microscope. "Electrical synapses
are like the dark matter of the brain," says Alexander Borst, director
at the MPI for Biological Intelligence, in foundation (i.f). Now a team
from his department has taken a closer look at this rarely explored
brain component: In the brain of the fruit fly Drosophila, they were
able to show that electrical synapses occur in almost all brain areas
and can influence the function and stability of individual nerve cells.
========================================================================== Neurons communicate via synapses, small contact points at which chemical messengers transmit a stimulus from one cell to the next. We may remember
this from biology class. However, that is not the whole story. In addition
to the commonly known chemical synapses, there is a second, little-known
type of synapse: the electrical synapse. "Electrical synapses are much
rarer and are hard to detect with current methods. That's why they have
hardly been researched so far," explains Georg Ammer, who has long been fascinated by these hidden cell connections. "In most animal brains, we therefore don't know even basic things, such as where exactly electrical synapses occur or how they influence brain activity." An electrical
synapse connects two neurons directly, allowing the electrical current
that neurons use to communicate, to flow from one cell to the next
without a detour. Except in echinoderms, this particular type of synapse
occurs in the brain of every animal species studied so far. "Electrical synapses must therefore have important functions: we just do not know
which ones!" says Georg Ammer.
Distribution in the brain To track down these functions, Ammer and his
two colleagues, Rene'e Vieira and Sandra Fendl, labelled an important
protein building block of electrical synapses. In the brain of fruit
flies, they were thus able to show that electrical synapses do not occur
in all nerve cells, but in almost all areas of the brain. By selectively switching off the electrical synapses in the area of visual processing,
the researchers could show that the affected neurons' reaction to certain stimuli is much weaker. Furthermore, without electrical synapses, some
nerve cell types became unstable and began to oscillate spontaneously.
"The results suggest that electrical synapses are important for diverse
brain functions and can play very different functional roles, depending on
the type of neuron," Ammer summarizes. "These synapses should therefore
also be integrated in connectome studies." The connectome is a map of
all neurons and their connections in a brain or brain area. Often, this information is reconstructed from electron microscope images -- where electrical synapses are largely invisible. How these can be integrated
into connectome investigations and what other secrets electrical synapses
hold, is subject for further studies.
========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Georg Ammer, Rene'e M. Vieira, Sandra Fendl, Alexander
Borst. Anatomical
distribution and functional roles of electrical synapses in
Drosophila.
Current Biology, 2022; DOI: 10.1016/j.cub.2022.03.040 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220405143540.htm
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