Transient receptor potential (TRP) channels are ion channels that are involved in sensing pain, temperature, and pressure. Vanilloid receptor 1 (TRPV1) channels mediate the response to noxious heat, and thus its activation results in sensations of burning and pain. TRPV1 can be activated by capsaicin, which is the major constituent of chili peppers.

Dirk Trauner and his team, Ludwig-Maximilians-Universität, Munich, Germany, wanted to investigate the synthesis and properties of photoswitchable azobenzene derivatives of known TRPV1 antagonists, as they postulated that the cis and trans configurations would have different antagonistic properties. A series of six compounds was synthesized and tested, and two of the azobenzene derivatives were found to act as trans antagonists upon voltage activation of TRPV1. Furthermore, one of these active compounds also acted as a cis antagonist upon stimulation with capsaicin.

Use of photoswitchable compounds shows that light can be used as an input signal to stimulate TRP channels, and that a photoswitchable antagonist and agonist can be used together in the optical control of ion channels.

• Optical Control of TRPV1 Channels,
  Marco Stein, Andreas Breit, Timm Fehrentz, Thomas Gudermann, Dirk Trauner,
  Angew. Chem. Int. Ed. 2013, 52, 9845–9848
  DOI: 10.1002/anie.201302530