Figure 5

Capsaicin-induced intracellular calcium signals and inward currents were compromised in TLR4 KO sensory neurons. A and B. DRG neurons from WT and TLR4 KO mice were cultured and treated with capsaicin (0.02-10 μM), and intracellular calcium was monitored by calcium imaging assays. Percentage of responding cells (A) and average net increase of [Ca⁺⁺]_i (Δ ratio (340 nm/380 nm)) in the responding population (B) are shown in graphs (n = 5 with 791, 232, 335, and 215 cells measured; *p < 0.005). Numbers of capsaicin-responding cells and average calcium [Ca⁺⁺]_i increase were compromised in TLR4 KO neurons. C. TRPA1-dependent calcium signals measured after AITC (1 μM) treatment. TRPA1-mediated calcium signals were not altered in TLR4 KO neurons. D. Capsaicin-induced inward currents measured by whole cell patch-clamp recording. Average inward current amplitude in capsaicin-responding TLR4 KO neurons (n = 43; *p < 0.005) was lower than in WT neurons (n = 39; *p < 0.005). E. TRPV1 expression was measured by immunohistochemistry using WT and TLR4 KO DRG sections. The percentage of TRPV1-expressing neurons and size distribution were not noticeably altered in TLR4 KO DRG. Representative pictures are shown. Scale bar, 25 μm.