Figure 3.

Menthol- and capsaicin-induced increases in intracellular Ca²⁺ levels and membrane currents in DRG neurons were reduced and enhanced, respectively, by PDBu (1 μm). a, Twenty selected neurons in a coverslip were individually tracked for changes in intracellular Ca²⁺ levels (F/F_o) while exposing them to menthol (30μm) and capsaicin (100 nm) before and after PDBu. Five neurons responded to menthol, two neurons responded to capsaicin, and one responded to both. Menthol responses were almost completely abolished(b), whereas capsaicin responses were significantly enhanced after PDBu(c). Note that capsaicin responses are larger and longer lasting. d, Time course of PDBu induced downregulation of menthol (100μm)-induced response. e, Menthol (100μm)-induced membrane currents were significantly reduced. f, Capsaicin (100 nm)-induced currents were significantly potentiated after pretreatment with PDBu. g, h, Summary graphs showing menthol-induced calcium responses are significantly reduced (p < 0.01), and capsaicin responses are significantly potentiated (100 nm capsaicin, p < 0.01; 1μm capsaicin, p < 0.05) after PDBu. i, j, Summary graph showing significant inhibition (p < 0.01) of menthol-induced and significant potentiation (p < 0.01) of capsaicin-induced currents after PDBu. Cap, Capsaicin; Men, menthol. Data are represented as mean ± SEM.