Petersen M, LaMotte R H
Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06510 USA.
Pain. 1993 Jul;54(1):37-42. doi: 10.1016/0304-3959(93)90097-9.
Capsaicin excites a subset of dorsal root ganglion (DRG) neurons by inducing an inward current. We have examined this inward current in response to high concentrations of protons in the external medium. The experiments were done in freshly dissociated DRG cells under whole-cell voltage-clamp conditions. The amplitude of the current evoked by capsaicin (200-300 nM) was increased with increasing concentrations of protons (pH 6.9-6.3). Increasing the acidification of the external medium from a physiological pH of 7.3 to 6.3 enhanced 7-fold the current induced by capsaicin (300 nM). Cells unresponsive to capsaicin in a physiological pH were also unresponsive to capsaicin in an acidic solution. There was a progressive decrease in the amplitude of the capsaicin-evoked current when the drug was repeatedly applied either at a physiological pH or an acidic pH of 6.3. Exposure of the cell to acidic solutions of capsaicin did not subsequently increase an evoked inward current when capsaicin was applied at a physiological pH nor did it lead to an inward current evoked by proton ions where there had been none. Our results suggest that increased proton concentrations in the extracellular medium could play an important modulatory role in the function of chemosensitive sensory neurons.
辣椒素通过诱导内向电流来激活一部分背根神经节（DRG）神经元。我们研究了在外部介质中高浓度质子作用下的这种内向电流。实验是在全细胞电压钳制条件下对新鲜解离的DRG细胞进行的。辣椒素（200 - 300 nM）诱发的电流幅度随着质子浓度增加（pH 6.9 - 6.3）而增大。将外部介质的酸化程度从生理pH 7.3提高到6.3，可使辣椒素（300 nM）诱导的电流增强7倍。在生理pH下对辣椒素无反应的细胞，在酸性溶液中对辣椒素也无反应。当在生理pH或酸性pH 6.3下重复应用该药物时，辣椒素诱发的电流幅度会逐渐降低。当在生理pH下应用辣椒素时，将细胞暴露于辣椒素酸性溶液中，随后并不会增加诱发的内向电流，而且在原本不存在由质子离子诱发内向电流的情况下，也不会导致产生内向电流。我们的结果表明，细胞外介质中质子浓度的增加可能在化学敏感感觉神经元的功能中发挥重要的调节作用。
