Capsaicin-activated channel has a key role in the sensation of thermal and inflammatory pain. During inflammation, redox state of cells will be changed by increased production of reactive oxygen species. Oxidation of amino acid residues in proteins can be caused by a variety of oxidizing agents produced in pathophysiological conditions. In the present study, we investigated the effect of chloramine-T, which preferentially oxidizes cysteine and methionine residues, on the activity of capsaicin channel using a a whole-cell patch clamp technique in cultured dorsal root ganglion (DRG) neurons from neonatal rats. Co-application of chloramine-T (3µM) with capsaicin (0.3µM) reversibly blocked capsaicin-activated inward current (Icap) in a dose-dependent manner. Dithiothreitol (DTT, 10 mM), a reducing agent, reversed the blocking effect of chloramine-T on Icap. These results suggest that chloramine-T could decrease Icap by oxidation of cysteine residue rather than methionine in the extracellular surface of capsaicin channel in small DRG neurons, which may play an important role in the regulation of inflammatory pain transmission.

Keywords: Capsaicin receptor, chloramine-T, oxidation, DRG neuron