Neomycin blocks capsaicin-evoked responses in rat dorsal root ganglion neurons

Small dorsal root ganglion (DRG) neurons are characterized by sensitivity to capsaicin. In acutely isolated rat DRG neurons, the effect of neomycin, one of the aminoglycoside antibiotics, on capsaicin-evoked current and voltage responses was examined using whole-cell patch-clamp recording. We showed for the first time that neomycin dose-dependently inhibited capsaicin-evoked currents with half-maximal inhibitory concentration at 130.60 microM (n=70). Under current-clamp condition, depolarization and firing rate evoked by capsaicin became weakened when neomycin was perfused to the neurons (n=10). Neomycin had no significant effect on the resting potentials of DRG neurons. These results suggest that neomycin could inhibit capsaicin-sensitive responses in small DRG neurons, which may contribute to neomycin-induced peripheral analgesia.