A genetically encoded sensor for in vivo imaging of orexin neuropeptides
Orexins (also called hypocretins) are hypothalamic neuropeptides that carry out essential functions in the central nervous system; however, little is known about their release and range of action in vivo owing to the limited resolution of current detection technologies. Here we developed a genetically encoded orexin sensor (OxLight1) based on the engineering of circularly permutated green fluorescent protein into the human type-2 orexin receptor. In mice OxLight1 detects optogenetically evoked release of endogenous orexins in vivo with high sensitivity. Photometry recordings of OxLight1 in mice show rapid orexin release associated with spontaneous running behavior, acute stress and sleep-to-wake transitions in different brain areas. Moreover, two-photon imaging of OxLight1 reveals orexin release in layer 2/3 of the mouse somatosensory cortex during emergence from anesthesia. Thus, OxLight1 enables sensitive and direct optical detection of orexin neuropeptides with high spatiotemporal resolution in living animals. ; The results are part of a project that has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 891959; to T.P.). We also acknowledge funding from the University of Zurich and the Swiss National Science Foundation (grant no. 310030_196455; to T.P.); Forschungskredit Candoc (to X.Z.); ETH Zurich (to D.B.); Swiss National Science Foundation (grant no. PCEFP3_181282; to M.S.); ERC-2017-STG (grant agreement no. 758448; to N.G.); Swiss National Science Foundation and ERC-2016-CoG (grant agreement no. 725850) (A.R.A.); University of Bern and Inselspital University Hospital (A.R.A. and M.H.S.); ERC-2014-CoG (grant agreement no. 647725) and National Institutes of Health Brain Initiative (U19 NS107464) (both to T.F.); H2020-ICT (grant agreement no. 101016787; to T.P. and T.F.). We thank J.-C. Paterna and the VVF of the Neuroscience Center Zurich for help with virus production, M. Drobizhev (Montana State ...