• Illuminating real-time brain dynamics of

    From ScienceDaily@1:317/3 to All on Thu Feb 10 21:30:42 2022
    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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