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Optical recording of action potentials in mammalian neurons using a microbial rhodopsin.

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.

Pubmed ID: 22120467


  • Kralj JM
  • Douglass AD
  • Hochbaum DR
  • Maclaurin D
  • Cohen AE


Nature methods

Publication Data

January 29, 2012

Associated Grants

  • Agency: NIBIB NIH HHS, Id: 1-R01-EB012498-01
  • Agency: NIH HHS, Id: DP2 OD007428
  • Agency: NIH HHS, Id: DP2 OD007428-01
  • Agency: NIBIB NIH HHS, Id: R01 EB012498
  • Agency: NIBIB NIH HHS, Id: R01 EB012498-02

Mesh Terms

  • Action Potentials
  • Animals
  • Cell Membrane
  • Fluorescent Dyes
  • HEK293 Cells
  • Halorhodopsins
  • Halorubrum
  • Hippocampus
  • Humans
  • Neurons
  • Optics and Photonics
  • Rats