Skip to main content
. Author manuscript; available in PMC: 2008 Aug 30.
Published in final edited form as: J Neurosci Methods. 2007 May 6;164(2):225–239. doi: 10.1016/j.jneumeth.2007.05.002

Fig. 1. Voltage-induced spectral shift of the blue VSDs.

Fig. 1

(A) Simultaneous whole-cell and optical (JPW-3080) recordings of three APs evoked by somatic current injection. In this and following panels both optical traces (532 nm and 658 nm) were obtained in the same ROI selected on a basal dendrite 45 – 65 μm from the soma. (B) Same as in A except different VSD (PY-1266). (C) Same as in A except different VSD (JPW-4090). (D) Schematic representation of a spectral shift, which is thought to underlie voltage-sensitivity of fast dyes. Absorption spectrum for JPW-3080 at hyperpolarized (grey contour) and depolarized membrane potential (black contour). Upon depolarization the absorbance maximum (vertical grey line - max) shifts toward longer wavelengths. Gray arrow indicates the direction of the electrochromic shift. Excitation wavelengths shorter than the max (e.g. 532 nm) generate negative optical signals (downward pointing arrow). Excitation wavelengths longer than max (e.g. 658 nm) produce positive optical signals (upward pointing arrow). (E) Same as in D except the absorption maximum of JPW-4090 is below 532 nm. Because both excitation lines (532 and 658 nm) are longer than max, both lines generate positive optical signals. Spectra contours shown in D and E are not real data. They are shown here to illustrate the impact of voltage-induced spectral shift on the size and polarity of voltage-sensitive dye signals.