Divalent cations induce desensitization of the heat activation pathway but not the capsaicin activation pathway. (A) Normalized current traces demonstrating transient activation of TRPV1 by 130 mM extracellular Ba²⁺ (left) or Mg²⁺ (right), followed by rapid desensitization. (B) Time course of whole-cell current (black trace) at +80 mV evoked first by heat (red trace below current trace) and subsequently by 3 µM capsaicin (black bar above current trace). (C) Same as for B, but in the presence of 130 mM Ba²⁺ instead of Na⁺. (D) Box-and-whisker plot of the ratio between current evoked by raising temperature to 45°C and current evoked by 3 µM capsaicin in a bath solution containing the indicated cations. ***, P < 0.001; n = 4–5. (E) Schematic gating diagram illustrating the separation of the capsaicin activation pathway and the heat–Mg²⁺–Ba²⁺ pathway (left). In the presence of Mg²⁺ or Ba²⁺, the heat–Mg²⁺–Ba²⁺ pathway is desensitized over time but the capsaicin activation remains functional (right).