Figure 3. ASIC channels are localized at the neurites of MNCs and can be directly activated by protons to elicit excitatory inward currents.

A-C) Images show immunoreactivity of ASIC1 (ASIC1-ir, A), ASIC2a (ASIC2a-ir, B), and ASIC3 (ASIC3-ir, C) on Aβ-afferent terminals in the regions of MNCs in three rat whisker hair follicles. D) Left, illustration of focal puff-application of protons to MNCs. Middle, two traces exemplify inward currents evoked by protons (pH 5 Krebs solution) while the 1^st nodes of rat MNCs were voltage-clamped at −70 mV (bottom) and 20 mV (top). Right, I-V curve of the currents evoked by protons (pH 5, n = 7) at different voltages. E) Summary data of the amplitudes of inward currents evoked by focal puff-application of Krebs solution with pH of 7.4, 6.5, 6, 5.5, and 5.0. Additionally, focal puff-application of 5-HT, norepinephrine (NE), glutamate, and acetylcholine (ACh) each at 2 mM did not evoke any current. The MNCs were voltage-clamped at −69 mV. F) Traces exemplify inward currents evoked by protons (pH 5) in the absence (control, left) and presence (right) of 200 μM amiloride. G) Pooled data of the amplitude of inward currents evoked by protons (pH 5) in the absence (control) and presence of 200 μM amiloride. H) Similar to G, except that diminazene (100 μM) was tested. The 1^st nodes were voltage-clamped at −69 mV. Data represent independent observations and mean ± SEM, *p < 0.05, paired Student’s t-test.