Star-cells 'shine' to make sense of touch
Astrocytic GABA fine-tunes tactile sensory acuity

Date:
September 8, 2020
Source:
Institute for Basic Science
Summary:
A research group reports a rather surprise finding as to how GABA
works to control the tactile sense. GABA, known for its inhibitory
function, actually enhances the sensory input processing by
accelerating the signal processing and sharpening the sensitivity
of signal magnitude.



FULL STORY ========================================================================== Parents might be familiar with their toddlers gotten messy with
flour. Feeling the soft texture of flour, kids can spend the whole
time and create, explore and learn through the messy play. Such tactile
sensory play is an effective stimulus for children's senses as the tactile system includes the entire network of skin. Thalamus in the brain is
where general sensory inputs are filtered in and out, yet it has remained elusive as to what specific mechanism fine-tunes the sense of touch.


==========================================================================
Led by Dr. C. Justin Lee at the Center for Cognition and Sociality
within the Institute for Basic Science (IBS) in Daejeon, South Korea,
and Dr. CHEONG Eunji at Yonsei University, the joint research team has
revealed the production pathway of the sense of touch. They found that
the persistent regulation (tonic) of ?-aminobutyric acid (GABA), which is
the main inhibitory transmitter in the astrocytes (star-shaped cells), generates the sense of touch. "Contrary to the conventional assumption, thalamic astrocytes were found to synthesize GABA using an enzyme
called diamine oxidase (DAO), rather than MAOB, previously known as a GABA-producing enzyme in cerebellar astrocytes," says KOH Wuhyun, first
author of the study. The research team also found that the production of
GABA is completed by an enzyme called Aldh1a1. The team confirmed that
the GABA produced is released through Best1 channel in astrocytes. They
also experimentally proved that astrocytic tonic GABA in the thalamus
controls our brain's acuity to make sense of touch.

The study reports a rather surprise finding as to how GABA works to
control the tactile sense. GABA, known for its inhibitory function,
actually enhances the sensory input processing by accelerating the signal processing and sharpening the sensitivity of signal magnitude. "The brain cannot accurately distinguish saturated neuronal signals. It is like
that too much exposure to light results in an overly bright photo. GABA's inhibitory action removes extreme values of signals and accentuates the information of each signal. This fine-tuning helps neurons to be more
sensible to various range of signals," explains Koh.

In behavioral experiments, the research team verified that tonic GABA dynamically controls tactile discrimination. They used sandpaper with
various grits; the smaller the grit number the more coarse the particles,
the larger the number the more fine. Its tactile-based novel object
recognition test showed that astrocytic knockdown models of Best1, DAO,
and Aldh1a1 reported a significantly lower discrimination ability compared
to the control group. The team also confirmed the effect of enhancement
of tonic GABA: Overly-charged models demonstrated a greatly enhanced
ability of discrimination. They were able to notify relatively small
change of textile, (?80). Normal models usually recognize a difference
of ?180 or more.

Co-corresponding author, Dr. CHEONG Eunji states, "Detecting a
small change of the surroundings marks the beginning of our cognitive
function. This study uncovered a novel mechanism of manipulating sensory acuity, offering a breakthrough for the study of sensory and cognitive functions." "This is the first example of how the astrocytes in the
thalamus actively participate in important cognitive processes, such as
sensory discrimination.

Astrocytes "shine" in the brain to actively engage in cognitive
functions, just as the stars in the night sky." notes Dr. C. Justin Lee, co-corresponding author.


========================================================================== Story Source: Materials provided by Institute_for_Basic_Science. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Hankyul Kwak, Wuhyun Koh, Sangwoo Kim, Kiyeong Song, Jeong-Im
Shin, Jung
Moo Lee, Elliot H. Lee, Jin Young Bae, Go Eun Ha, Ju-Eun Oh, Yongmin
Mason Park, Sunpil Kim, Jiesi Feng, Seung Eun Lee, Ji Won Choi,
Ki Hun Kim, Yoo Sung Kim, Junsung Woo, Dongsu Lee, Taehwang Son,
Soon Woo Kwon, Ki Duk Park, Bo-Eun Yoon, Jaeick Lee, Yulong Li,
Hyunbeom Lee, Yong Chul Bae, C. Justin Lee, Eunji Cheong. Astrocytes
Control Sensory Acuity via Tonic Inhibition in the Thalamus. Neuron,
2020; DOI: 10.1016/ j.neuron.2020.08.013 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200908113333.htm

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