Fig. 2: Bidirectional optogenetic activation and inhibition of neurons with red and blue light stimulation.

a Schematic strategy for co-expressing ChrimsonR and stGtACR2 in the ventral tegmental area (VTA) of DAT-cre mice. b Immunostained fluorescence images of the VTA region expressing DAPI (blue), stGtACR2 (green), and ChrimsonR (red) and a merged image, 3 weeks after viral injection. c Zoomed view showing cells co-expressing stGtACR2 (green) and ChrimsonR (red). d Percentages of stGtACR2-, ChrimsonR- and co-expressing neurons among DAPI cells in the VTA (mean ± s.e.m., 3 slices per mouse, n = 3 mice). e Illustration of the experiment setup with combined blue (480 nm) and red (633 nm) laser beams (spot diameter ~1 mm) for optogenetic stimulating brain slices during patch-clamp recordings in vitro. f Example traces showing neural activation by pulsed red light at different irradiances (20 Hz, 10-ms pulse, 20-pulse train). g Activated spike probability as a function of red irradiances (mean ± s.e.m., n = 4 cells). h Example photocurrents of neurons at membrane potentials varied from −105 to −5 mV (bottom to top), under continuous blue light illumination (duration 5 s, irradiance 8 mW/mm²). i Example traces of neural inhibition by continuous blue light at different irradiances (duration 0.5 s). j Inhibited spike probability as a function of blue irradiances (mean ± s.e.m., n = 5 cells). k Traces presenting bidirectional spike activation and inhibition with alternating red and blue illuminations (Patching current +90 pA; Red: duration 3 s, 20 Hz, 10-ms pulse, 2.2 mW/mm²; Blue: duration 3 s, 8.5 mW/mm²). l Example traces of neural activities with simultaneous red and blue illuminations at different irradiances (duration 6 s). m Summarized plot of measured spike probability (normalized mean values) as a function of red and blue irradiances (n = 5 cells). The stars indicate the position of the four example traces shown in (l). Source data are provided as a Source Data file.