NSAIDs modulate GABA-activated currents via Ca2+-activated Cl- channels in rat dorsal root ganglion neurons

摘要

The ability of non-steroidal anti-inflammatory drugs (NSAIDs) to modulate gamma-aminobutyrate (GABA) -activated currents via Ca2+-activated Cl-channels in rat dorsal root ganglion neurons (DRG), was examined in the present study. During the preparation of DRG neurons harvested from Sprague-Dawley rats, the whole-cell recording technique was used to record the effect of NSAIDs on GABA-activated inward currents, and the expression levels of the TMEM16A and TMEM16B subunits were revealed. In the event that DRG neurons were pre-incubated for 20 sec with niflumic acid (NFA) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) prior to the administration of GABA, the GABA-induced inward currents were diminished markedly in the majority of neurons examined (96.3%). The inward currents induced by 100 mu mol/l GABA were attenuated by (0 +/- 0.09%; neurons = 4), (5.32 +/- 3.51%; neurons = 6), (21.3 +/- 4.00%; neurons = 5), (33.8 +/- 5.20%; neurons = 17), (52.2 +/- 5.10%; neurons = 4) and (61.1 +/- 4.12%; neurons = 12) by 0.1, 1, 3, 10, 30 and 100 mu mol/l NFA, respectively. The inward currents induced by 100 mumol/l GABA were attenuated by (13.8 +/- 6%; neurons = 6), (23.2 +/- 14.7%; neurons = 6) and (29.7 +/- 9.1%; neurons = 9) by 3, 10 and 30 mu mol/l NPPB, respectively. NFA and NPPB dose-dependently inhibited GABA-activated currents with half maximal inhibitory concentration (IC50) values of 6.7 and 11 mu mol/l, respectively. The inhibitory effect of 100 mu mol/l NFA on the GABA-evoked inward current were also strongly inhibited by nitrendipine (NTDP; an L-type calcium channel blocker), 1,2-bis(2-aminophenoxy) ethane-N, N, N', N' -tetraacetic acid tetrakis (a highly selective calcium chelating reagent), caffeine (a widely available Ca2+ consuming drug) and calcium-free extracellular fluid, in a concentration-dependent manner. Immunofluorescent staining indicated that TMEM16A and TMEM16B expression was widely distributed in DRG neurons. The results suggest that NSAIDs may be able to regulate Ca2+-activated chloride channels to reduce GABAA receptor-mediated inward currents in DRGs.