HXA3 produces direct activation of TRPV1 and TRPA1 in sensory neurons. (A) Representative micrographs of cultured rat sensory neurons before (Upper) and after (Lower) application of 1 μM HXA3. Arrowheads, Fura-2–loaded cells exhibiting Ca2+ mobilization in response to HXA3. (Scale bars, 50 μm.) (B) Representative traces of HXA3-evoked calcium responses in rat sensory neurons and attenuation by the TRPA1 antagonist HC030031 (Upper) or the TRPV1 antagonist AMG9810 (Lower). Peak Ca2+ responses represent mean change in fluorescence ratio (Δ340/380) ± SEM. (C) HXA3-evoked Ca2+-responses were reduced by HC030031 (10 μM) (VEH, 0.117 ± 0.01 vs. HC030031, 0.001 ± 0.02; ***P < = 0.001, n = 16 cells, 4 rats) and AMG 9810 (1 μM) (VEH, 0.159 ± 0.03 vs. AMG9810 0.061 ± 0.03; *P < 0.05, n = 5 cells, 3 rats). (D) HXA3 (1 μM) also increased calcium mobilization in HEK-TRPA1-tet [TRPA1(+) Induced, 0.077 ± 0.008 vs. TRPA1(−) Uninduced control, 0.020 ± 0.004; ***P < 0.001, n = 4 cells] and in CHO-TRPV1 cells [TRPV1(+) 0.070 ± 0.001 vs. TRPV1(−) CHO control, 0.012 ± 0.001; *P < 0.05, n = 3–5 cells]. (E) Representative traces of HXA3-evoked calcium responses in mouse sensory neurons from WT (Top) and attenuation in TRPA1 (Middle), or TRPV1 knockout (KO) (Bottom). (F) Percent of WT, TRPA1, or TRPV1 KO neurons in which 1 μM HXA3 increased free intracellular Ca2+ levels. (WT, 15.2 ± 4.9% n = 42 cells; TRPA1 KO, 0.0 ± 0.0%, n = 34 cells; TRPV1 KO, 1.1 ± 1.1%; n = 51 cells; *P < = 0.05, 3 mice per group). Cell viability was confirmed using 50 mM K+; functional TRPV1 or TRPA1 receptors were verified with 500 nM capsaicin or 5 μM icilin, respectively. VEH, artificial CSF.