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. 2016 Aug 3;6:30570. doi: 10.1038/srep30570

Figure 1. Intraneural injection of AAV6-hSyn-SwiChR-eYFP enables optogenetic inhibition of nociceptors during illumination in vitro and in vivo.

Figure 1

(a) SwiChR-eYFP+ neurons project to i), v) lamina I/IIo in the spinal cord, are ii) unmyelinated, form free nerve endings in the iii) glabrous and iv) hairy paw and vi) are small in diameter. vi) Histogram based on 3 DRGs from 2 mice. n = 362 SwiChR+ neurons (green), n = 1078 SwiChR− neurons (grey). Scale bars: spinal cord (i): 250 μm, spinal cord (iv): 500 μm, nerve: 25 μm, paw (iii): 150 μm, paw (iv): 200 μm. Colors: i), ii), and v) magenta: myelin, green: SwiChR-eYFP. iii), iv) magenta: PGP9.5, green: SwiChR-eYFP. (b) i) Representative DRG sections showing overlap between SwiChR-eYFP and calcitonin gene-related peptide (CGRP), substance P (SP), isolectin B4 (IB4) binding neurons, and neurofilament-200 (NF200). Colors: green: SwiChR-eYFP, magenta: marker, white: overlap, arrowheads: co-expressing neurons. Scale bar: 100 μm. ii), and iii) Quantification, showing ii) percentage of SwiChR-eYFP+ neurons expressing a marker, and iii) percentage of neurons expressing a marker that co-express SwiChR-eYFP. Group data from >300 SwiChR-eYFP+ or marker + neurons from 3 different DRG sections from different mice. (c) i) Reversal potential of SwiChR relative to measured VAP and Vrest. (P = 0.0002, pH = 7.4: n = 14 cells for Vrev , n = 15 cells for VAP , n = 21 cells for Vrest ; pH = 6.0: n = 8 cells for Vrev , n = 7 cells for VAP , n = 9 cells for Vrest). Gray zones: mean ± SEM. ii) Photocurrent amplitudes at VAP . (P = 0.000174, pH = 7.4: n = 15 cells; pH = 6.0: n = 9). iii) Changes in cellular input resistance during and after blue light application normalized to pre-light value (pH = 7.4: P = 0.0018, n = 12 cells; pH = 6.0: P = 0.0050, n = 6 cells). (d) Mechanical and thermal thresholds and latencies increase significantly during blue-light illumination in SwiChR+ and iC1C2+ mice, but not YFP+ mice. *P < 0.05, **P < 0.01, ***P < 0.001.