title: Infrared light excites cells by changing their electrical capacitance.
abstract: Optical stimulation has enabled important advances in the study of brain function and other biological processes, and holds promise for medical applications ranging from hearing restoration to cardiac pace making. In particular, pulsed laser stimulation using infrared wavelengths >1.5 μm has therapeutic potential based on its ability to directly stimulate nerves and muscles without any genetic or chemical pre-treatment. However, the mechanism of infrared stimulation has been a mystery, hindering its path to the clinic. Here we show that infrared light excites cells through a novel, highly general electrostatic mechanism. Infrared pulses are absorbed by water, producing a rapid local increase in temperature. This heating reversibly alters the electrical capacitance of the plasma membrane, depolarizing the target cell. This mechanism is fully reversible and requires only the most basic properties of cell membranes. Our findings underscore the generality of pulsed infrared stimulation and its medical potential.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Chicago, 929 E. 57th Street, GCIS W244, Illinois 60637, USA.
authors.forename: Mikhail G
authors.initials: MG
authors.lastname: Shapiro
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Homma
authors.forename: Sebastian
authors.initials: S
authors.lastname: Villarreal
authors.forename: Claus-Peter
authors.initials: CP
authors.lastname: Richter
authors.forename: Francisco
authors.initials: F
authors.lastname: Bezanilla
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology* / Q000528:radiation effects*; D025802:Electric Capacitance; D057809:HEK293 Cells; D006358:Hot Temperature; D006801:Humans; D007259:Infrared Rays; D007834:Lasers; D008051:Lipid Bilayers / Q000378:metabolism / Q000528:radiation effects*; D009865:Oocytes / Q000502:physiology / Q000528:radiation effects; D014867:Water / Q000737:chemistry / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D008051:Lipid Bilayers; D014867:Water