Figure 8.

Proton-evoked inward currents in Nav1.8-ChR2-EYFP–negative Aβ-afferent neurons in L4 DRGs of mice. A, Experimental setting for recordings of proton-evoked currents in Nav1.8-ChR2-EYFP–negative Aβ-afferent neurons in L4 DRGs. An L4 DRG with an attached peripheral afferent bundle was anchored in a recording chamber. Whole-cell patch–clamp recordings were made from DRG neurons. Electrical stimulation was applied to the peripheral afferent bundle with a suction electrode to evoke APs. As illustrated in A, an acidified Krebs’ solution, pH 5, was applied to the recorded neuron. B, C, Image shows L4 DRG neurons under 40× bright-field (B) and fluorescent microscopy (C). An asterisk in each image indicates a large-sized Nav1.8-ChR2-EYFP–negative Aβ-afferent neuron. The shadow of a recording electrode can be seen on the right side of the asterisk. D, Overlay image of B and C to show the Nav1.8-ChR2-EYFP–negative (asterisk indicated) and Nav1.8-ChR2-EYFP–positive (green color) Aβ-afferent neurons. E, Sample trace shows an AP evoked by electrical stimulation to an afferent nerve bundle at its peripheral site, and the AP was recorded from a Nav1.8-ChR2-EYFP–negative Aβ-afferent neuron. F–H, Pooled data show CV (F), soma diameters (G), and AP widths (H) of Nav1.8-ChR2-EYFP–negative Aβ-afferent neurons. I, Sample trace shows an inward current evoked by protons, pH 5 (Krebs’ solution), in a Nav1.8-ChR2-EYFP–negative Aβ-afferent neuron. J, The percentage of Nav1.8-ChR2-EYFP–negative Aβ-afferent neurons being proton-responsive (n = 16) and not proton-responsive (n = 9). K, Pooled data of proton-evoked inward currents in Nav1.8-ChR2-EYFP–negative Aβ-afferent neurons in L4 DRGs (n = 16). Data represent individual observations and mean ± SEM.