Fig. 3. Effect of lyral on Ca²⁺ levels in HEK293 cells expressing MOR23. (A) Chemical structures of odorants used in this study. (B) Effect of various treatments on Ca²⁺ levels. (top) Pseudocolored images of fura-2-loaded HEK293 cells stimulated with 3 mM odorant or isoproterenol (Iso). Iso, which causes Ca²⁺ increase in HEK293 cells via intrinsic ß-adrenergic receptors and transfected G15, was used as a control for G15 co-transfection. Scale bar, 20 µm. (bottom) The Ca²⁺ response profile of MOR23-expressing HEK293 cells. Odorants were applied for 15 seconds during the time indicated by the bars, and cells were continuously washed with buffer between stimulant applications. B, bourgenonal; H, heptanal; LY, lyral.