Calcium imaging indicates functional expression of P2X and TRPV1 receptors. A, examples of Ca2+ transients in mouse TG neurons activated by 2 s application of 10 μM α, β-meATP or 1 μM capsaicin. a, example of cell responding to α, β-meATP only ('purinergic phenotype'); b, responding to capsaicin only ('vanilloid phenotype'); c, responding to both agonists ('mixed phenotype'). All cells respond to pulse application of KCl. B, number of neurons sensitive to α, β-meATP (regardless of their response to capsaicin), to capsaicin (regardless of their response to α, β-meATP) or to both agonists, for mouse (n = 346; left) and rat (n = 41; right) TG neurons. Neurons (kept in culture for 24 h) were identified by their responsiveness to 15 mM KCl (1 s), while satellite cells and fibroblasts did not respond to this agent. Note that the percent of cells responding to capsaicin was higher in the rat (55%) than in the mouse (33%).