Caged Vanilloid Ligands for Activation of TRPV1 Receptors by 1- and 2-Photon Excitation
Citations Over TimeTop 25% of 2006 papers
Abstract
Nociceptive neurons in the peripheral nervous system detect noxious stimuli and report the information to the central nervous system. Most nociceptive neurons express the vanilloid receptor, TRPV1, a nonselective cation channel gated by vanilloid ligands such as capsaicin, the pungent essence of chili peppers. Here, we report the synthesis and biological application of two caged vanilloids: biologically inert precursors that, when photolyzed, release bioactive vanilloid ligands. The two caged vanilloids, Nb-VNA and Nv-VNA, are photoreleased with quantum efficiency of 0.13 and 0.041, respectively. Under flash photolysis conditions, photorelease of Nb-VNA and Nv-VNA is 95% complete in approximately 40 micros and approximately 125 micros, respectively. Through 1-photon excitation with ultraviolet light (360 nm), or 2-photon excitation with red light (720 nm), the caged vanilloids can be photoreleased in situ to activate TRPV1 receptors on nociceptive neurons. The consequent increase in intracellular free Ca(2+) concentration ([Ca(2+)](i)) can be visualized by laser-scanning confocal imaging of neurons loaded with the fluorescent Ca(2+) indicator, fluo-3. Stimulation results from TRPV1 receptor activation, because the response is blocked by capsazepine, a selective TRPV1 antagonist. In Ca(2+)-free extracellular medium, photoreleased vanilloid can still elevate [Ca(2+)](i), which suggests that TRPV1 receptors also reside on endomembranes in neurons and can mediate Ca(2+) release from intracellular stores. Notably, whole-cell voltage clamp measurements showed that flash photorelease of vanilloid can activate TRPV1 channels in <4 ms at 22 degrees C. In combination with 1- or 2-photon excitation, caged vanilloids are a powerful tool for probing morphologically distinct structures of nociceptive sensory neurons with high spatial and temporal precision.
Related Papers
- → Analgesic transient receptor potential vanilloid‐1‐active compounds inhibit native and recombinant T‐type calcium channels(2019)19 cited
- → Inhibition by capsazepine of resiniferatoxin- and capsaicin-induced contractions of guinea pig trachea.(1994)65 cited
- → Stimulation by Capsaicin of Duodenal HCO3− Secretion via Afferent Neurons and Vanilloid Receptors in Rats: Comparison with Acid-Induced HCO3− Response(2003)36 cited
- → Capsaicin-induced desensitization is prevented by capsazepine but not by ruthenium red in guinea pig bronchi(1998)9 cited
- → Using the nematode C. elegans to assay the effectiveness of novel anti‐nociceptive compounds targeting transient receptor potential vanilloid 1 (TRPV1) channels(2008)