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

Small dorsal root ganglion (DRG) neurons are characterized by sensitivity t o capsaicin. In acutely isolated rat DRG neurons, the effect of neomycin, o ne of the aminoglycoside antibiotics, on capsaicin-evoked current and volta ge responses was examined using whole-cell patch-clamp recording. We showed for the first time that neomycin dose-dependently inhibited capsaicin-evok ed currents with half-maximal inhibitory concentration at 130.60 muM (n=70) . Under current-clamp condition, depolarization and firing rate evoked by c apsaicin became weakened when neomycin was perfused to the neurons (n= 10). Neomycin had no significant effect on the resting potentials of DRG neuron s. These results suggest that neomycin could inhibit capsaicin-sensitive re sponses in small DRG neurons, which may contribute to neomycin-induced peri pheral analgesia. (C) 2001 Published by Elsevier Science Ireland Ltd.