CAPSAICIN ACTIVATED CURRENTS IN RAT DORSAL-ROOT GANGLION-CELLS

Capsaicin is a pungent-tasting compound produced by plants in the Caps ium family that activates a subset of primary afferent neurons associa ted with pain and thermoreception. Previous studies from dorsal root g anglion (DRGs) neurons suggest that many of capsaicin's physiological responses are a consequence of its activating a cation-selective curre nt, To further characterize the responses to capsaicin whole-cell patc h-clamp measurements were performed on rat DRGs to which 0.1-10 mu M c apsaicin was continuously applied. The capsaicin-activated currents ex hibited marked variability in their thresholds, amplitude (to 15 nA), rates of desensitization, and the number of distinct maxima in the evo ked current. Similar responses were found in rat trigeminal ganglion c ells. The heterogeneity in the magnitude of the currents evoked by 0.1 mu M capsaicin likely reflects different types of capsaicin-sensitive neurons; a result consistent with in vitro extracellular recordings f rom capsaicin-sensitive sensory afferents (Seno and Dray 1993).