Illuminating real-time brain dynamics of neuropeptides with a
fluorescent biosensor
Date:
February 10, 2022
Source:
University of Zurich
Summary:
Neuropeptides play fundamental roles in modulating cellular and
circuit functions within the brain. One such signaling molecule
-- orexin - - regulates arousal and wakefulness, and its failure
can lead to constant daytime sleepiness (narcolepsy). Researchers
have now developed a fluorescent orexin biosensor to observe this
molecule 'live' in the living mouse brain.
FULL STORY ==========================================================================
In the brain, billions of neural cells act in concert to coordinate both
basic and higher functions of the organism. They use a special language
to communicate with each other: molecules known as neuropeptides or neurotransmitters. One example of such a signaling molecule system
is orexin.
Normally, it regulates arousal, wakefulness, motivation and
appetite. Defects in the release or sensing of orexin neuropeptides cause,
both in humans and in animals, a disease called narcolepsy. Affected individuals suffer from overwhelming daytime drowsiness and often exhibit cataplexic states, in which they remain conscious but are unable to
control body movement, resulting in a sort of paralysis.
========================================================================== Shedding light on the internal workings of the mouse brain Tommaso
Patriarchi from the Institute of Pharmacology and Toxicology at the
University of Zurich (UZH) and his team have now developed a genetically encoded biosensor whose fluorescent properties enable them to study
orexin action and release mechanisms "live" and with high-resolution
in the brain of living mice. "The direct link between this particular neuropeptide system and its dramatic alteration in human brain functions
in narcolepsy, led us to study orexin in more detail," says Patriarchi.
The new orexin biosensor named "OxLight1" is based on a specially
designed green fluorescent protein integrated into the human orexin
receptor. "Marking the receptor with a fluorescent protein makes it
visible under the microscope.
When the neuropeptide binds to the receptor, it makes it light up,"
Patriarchi adds. OxLight1 thus offers practically a real-time outlook
on orexin release in living animals like the mouse.
Illuminating previously invisible aspects of healthy brain function
"To understand how neuropeptides systems like orexin act to maintain a
healthy brain function, we need to be able to first observe the messages carried by these neuropeptides and then learn to interpret them,"
says Patriarchi. Up to now, this has been practically impossible due
to the lack of tools that could provide a readout with high spatial and temporal resolution. The researchers therefore used their new biosensor to investigate the relationship between neuronal activity and neuropeptide
release in living animals, one of the most pressing and long-sought
questions in neurophysiology that has remained elusive until now.
They showed that the level of orexin release correlates with both
frequency and duration of neuronal activation. "The exquisite sensitivity
and speed of OxLight1 allowed us to track endogenous orexin release
associated with natural behaviors such as spontaneous running or acute
stress," says Patriarchi. As a result, they were able to demonstrate in
the living brain that orexin signals can occur in the form of relatively short-lived, or "phasic" bursts of release.
Investigating the neural disease mechanisms of narcolepsy The team then investigated orexins dynamics across sleep/wake transitions. By combining photometry imaging of orexin dynamics and neuronal activity recordings
to score the sleep status of the animals, the researchers observed for
the first time that a rapid drop in orexin levels occurs during REM sleep
of the mice. Further work with colleagues from the Istituto Italiano di Tecnologia in Italy, experts in two-photon microscopy, revealed another
so far unknown process: spatially localized orexin fluctuations occurring
in the somatosensory cortex upon awakening from anesthesia. This latter collaborative work was conducted within the framework of the recently
awarded European project DEEPER.
"After deciphering orexin release and neuronal activity in the healthy
brain, we are now using OxLight1 to investigate the mechanisms of brain diseases like narcolepsy and addiction," says Tommaso Patriarchi. This
research is the first outcome of a project for which Tommaso Patriarchi received an ERC Starting Grant in 2020.The biosensors that his team has developed are now being used to investigate brain function in laboratories around the world. By continuing to expand their neuro-technological
toolbox the researchers also aim to establish next-generation screening
assays for drug development.
special promotion Explore the latest scientific research on sleep and
dreams in this free online course from New Scientist -- Sign_up_now_>>> ========================================================================== Story Source: Materials provided by University_of_Zurich. Note: Content
may be edited for style and length.
========================================================================== Journal Reference:
1. Loi"c Duffet, Seher Kosar, Mariangela Panniello, Bianca Viberti,
Edward
Bracey, Anna D. Zych, Arthur Radoux-Mergault, Xuehan Zhou,
Jan Dernic, Luca Ravotto, Yuan-Chen Tsai, Marta Figueiredo,
Shiva K. Tyagarajan, Bruno Weber, Miriam Stoeber, Nadine Gogolla,
Markus H. Schmidt, Antoine R. Adamantidis, Tommaso Fellin, Denis
Burdakov, Tommaso Patriarchi. A genetically encoded sensor for in
vivo imaging of orexin neuropeptides.
Nature Methods, 2022; 19 (2): 231 DOI: 10.1038/s41592-021-01390-2 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/02/220210114018.htm
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