Second Harmonic Generation in Neurons: Electro-Optic Mechanism of Membrane Potential Sensitivity

Second harmonic generation (SHG) from membrane-bound chromophores can be used to image membrane potential in neurons. We investigate the biophysical mechanism responsible for the SHG voltage sensitivity of the styryl dye FM 4-64 in pyramidal neurons from mouse neocortical slices. SHG signals are exq...

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Bibliographic Details
Published in:Biophysical journal 2007-09, Vol.93 (5), p.L26-L28
Main Authors: Jiang, Jiang, Eisenthal, Kenneth B., Yuste, Rafael
Format: Article
Language:English
Subjects:
Action Potentials
Animals
Biophysical Letters
Biophysics
Biophysics - methods
Calibration
Electrochemistry - methods
Electrodes
Kinetics
Lasers
Membrane Potentials
Membranes
Models, Biological
Models, Statistical
Neurons
Neurons - metabolism
Optics and Photonics
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Summary:Second harmonic generation (SHG) from membrane-bound chromophores can be used to image membrane potential in neurons. We investigate the biophysical mechanism responsible for the SHG voltage sensitivity of the styryl dye FM 4-64 in pyramidal neurons from mouse neocortical slices. SHG signals are exquisitely sensitive to the polarization of the incident laser light. Using this polarization sensitivity in two complementary approaches, we estimate a ∼36° tilt angle of the chromophore to the membrane normal. Changes in membrane potential do not affect the polarization of the SHG signal. The voltage response of FM 4-64 is faster than 1 ms and does not reverse sign when imaged at either side of its absorption peak. We conclude that FM 4-64 senses membrane potential through an electro-optic mechanism, without significant chromophore membrane reorientation, redistribution, or spectral shift.
ISSN:0006-3495
1542-0086
DOI:10.1529/biophysj.107.111021