The ligand that came from within.

Recent evidence suggests that the endogenous activators of neuronal vanilloid (capsaicin) receptors should be sought inside, not outside, the neuron. 12-Lipoxygenase metabolites of arachidonic acid, produced by pain-inducing mediators such as bradykinin, might trigger vanilloid receptor activation by interacting with an intracellular site on the receptor. Are these lipid-like second messengers the long-sought endogenous vanilloids?