TNCB triggers ATP release in the skin. Mice received ATP-dependent luciferase-expressing HEK293 cells into the right ear pinna. The injected ear was painted 24 h later with acetone or 3% TNCB in acetone, and luciferin was injected i.p. immediately after painting. ATP was injected into the ear pinna as a positive control. Imaging was performed 10 min later. One out of three representative experiments is shown (top). Bioluminescence was quantified for the different conditions (bottom).