Neurons communicate through electrochemical signaling within a complex network. These signals are composed of changes in membrane potentials and are traditionally measured with the aid of (toxic) fluorescent labels or invasive electrical probes. Here, we demonstrate an improvement in label-free second harmonic neuroimaging sensitivity by ~3 orders of magnitude using a wide-field medium repetition rate illumination. We perform a side-by-side patch-clamp and second harmonic imaging comparison to demonstrate the theoretically predicted linear correlation between whole neuron membrane potential changes and the square root of the second harmonic intensity. We assign the ion induced changes to the second harmonic intensity to changes in the orientation of membrane interfacial water, which is used to image spatiotemporal changes in the membrane potential and K+ ion flux. We observe a non-uniform spatial distribution and temporal activity of ion channels in mouse brain neurons.
Bibliographical noteFunding Information:
This work was supported by the Julia Jacobi Foundation and the Swiss National Foundation (grant number 200021_146884). The authors would like to thank E. Ruchti, E. Gasparetto and M. Wirth for providing the neuronal cultures, B.S. Sermet for help with the patch-clamp measurements and P. Marquet and I. Allaman for discussions.
© 2018, The Author(s).
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)