Figure 1.

Oleocanthal excites trigeminal neurons through TRPA1 channel activation. a, OC (5 μm) evokes calcium influx into cultured rat trigeminal neurons as assessed by fura-2 ratiometric imaging (F₃₄₀/F₃₈₀). In a, the representative trace of one neuron shows that cells sensitive to OC are also activated by AITC (50 μm). The horizontal bars indicate the duration of compound application. The 40 mm KCl solutions were applied as a control for neuronal activity. b, Dose–response curve for OC-evoked responses in rat trigeminal neurons. The curve was generated by averaging the peak amplitude of the responses (fura-2 ratio) of all the OC-sensitive cells (n > 18 /data points). OC chemical structure is indicated on the graph. c, Sensitivity to OC (5 μm) is correlated to sensitivity to AITC (50 μm) in trigeminal neurons (n > 40 per experiment). d, Rodent trigeminal neurons deprived of functioning TRPA1 are unresponsive to OC. HC-030031 (HC) (20 μm) inhibited 5 μm OC-evoked rat trigeminal neuron activation (examined cells, n = 191) (left) and neurons from TRPA1^−/− mice (n = 187, from 5 mice) are not excited by OC (right). *p < 0.05 versus control [vehicle for left panel; wild-type (WT) for right panel], t test. Error bars indicate SEM.