title: Optical recording of action potentials in mammalian neurons using a microbial rhodopsin.
abstract: Reliable optical detection of single action potentials in mammalian neurons has been one of the longest-standing challenges in neuroscience. Here we achieved this goal by using the endogenous fluorescence of a microbial rhodopsin protein, Archaerhodopsin 3 (Arch) from Halorubrum sodomense, expressed in cultured rat hippocampal neurons. This genetically encoded voltage indicator exhibited an approximately tenfold improvement in sensitivity and speed over existing protein-based voltage indicators, with a roughly linear twofold increase in brightness between -150 mV and +150 mV and a sub-millisecond response time. Arch detected single electrically triggered action potentials with an optical signal-to-noise ratio >10. Arch(D95N) lacked endogenous proton pumping and had 50% greater sensitivity than wild type but had a slower response (41 ms). Nonetheless, Arch(D95N) also resolved individual action potentials. Microbial rhodopsin-based voltage indicators promise to enable optical interrogation of complex neural circuits and electrophysiology in systems for which electrode-based techniques are challenging.
authors: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, USA.
authors: Joel M
authors: JM
authors: Kralj
authors: Adam D
authors: AD
authors: Douglass
authors: Daniel R
authors: DR
authors: Hochbaum
authors: Dougal
authors: D
authors: Maclaurin
authors: Adam E
authors: AE
authors: Cohen
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D057809:HEK293 Cells; D025602:Halorhodopsins / Q000235:genetics / Q000378:metabolism*; D055352:Halorubrum / Q000737:chemistry; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D009474:Neurons / Q000502:physiology*; D055095:Optics and Photonics; D051381:Rats
chemical_list: D005456:Fluorescent Dyes; D025602:Halorhodopsins