Hagenacker Tim, Büsselberg Dietrich
Institut für Physiologie, Universitätsklinikum Essen, Essen, Germany.
J Peripher Nerv Syst. 2007 Dec;12(4):277-84. doi: 10.1111/j.1529-8027.2007.00149.x.
Modulation of intracellular calcium (Ca2+) has a major impact on processing of nociceptive signals. While activation of the transient receptor potential vanilloid-1 (TRPV-1) receptor/channel complex increases Ca2+ by Ca2+ entry from the extracellular space, as well as by Ca2+ release from intracellular stores, the Ca2+ entry through voltage-activated calcium channels (VACCs) is modulated simultaneously. To clarify the relations between Ca2+ and the activation of TRPV-1 receptor and VACC currents [I(TRPV-1) and I(Ca(V))], we performed voltage clamp experiments using Ba2+ as well as Ca2+ as a charge carrier. The TRPV-1 receptor was activated by the application of 0.5 microM capsaicin, and the currents through TRPV-1 and VACC [I(TRPV-1) and I(Ca(V))] were measured either when Ca2+ release from intracellular stores was pharmacologically promoted or prevented. With Ba2+ as the divalent charge carrier, capsaicin (0.5 microM) reduced I(Ca(V)) (elicited by a depolarization to 0 mV) to 52.7 +/- 4.5% of baseline, and the elicited current through the TRPV-1 receptor/channel complex was 6.6 +/- 0.9% [relative to peak I(Ca(V))]. These currents were significantly different when Ca2+ was used as charge carrier: the I(Ca(V)) reductions were decreased to 17.8 +/- 5.9% of baseline, while the I(TRPV-1) was as high as 57.1 +/- 9.1% of I(Ca(V)). Increases of Ca2+ by releasing Ca2+ from intracellular stores (using caffeine, 10 mM) before the application of capsaicin increased the I(TRPV-1) (14.1 +/- 7%), while the I(Ca(V)) was decreased to 51.6 +/- 4.9% compared with control. A preexperimental partial reduction of the Ca2+ release from the stores by dantrolene (5 microM) resulted in less pronounced effects [24.5 +/- 8.8%, relative to peak I(Ca(V))] for I(TRPV-1), and a reduction to 35.4 +/- 3% of baseline for I(Ca(V)) after capsaicin application.
细胞内钙（Ca2+）的调节对伤害性信号的处理有重大影响。瞬时受体电位香草酸受体1（TRPV-1）受体/通道复合物的激活会通过细胞外空间的Ca2+内流以及细胞内钙库的Ca2+释放来增加Ca2+，同时通过电压门控钙通道（VACC）的Ca2+内流也会受到调节。为了阐明Ca2+与TRPV-1受体激活及VACC电流[I(TRPV-1)和I(Ca(V))]之间的关系，我们使用Ba2+以及Ca2+作为电荷载体进行了电压钳实验。通过施加0.5微摩尔辣椒素激活TRPV-1受体，并在药理学上促进或阻止细胞内钙库释放Ca2+的情况下测量通过TRPV-1和VACC的电流[I(TRPV-1)和I(Ca(V))]。以Ba2+作为二价电荷载体时，辣椒素（0.5微摩尔）将I(Ca(V))（由去极化至0毫伏引发）降低至基线的52.7±4.5%，通过TRPV-1受体/通道复合物引发的电流为6.6±0.9%[相对于I(Ca(V))峰值]。当使用Ca2+作为电荷载体时，这些电流有显著差异：I(Ca(V))的降低降至基线的17.8±5.9%，而I(TRPV-1)高达I(Ca(V))的57.1±9.1%。在施加辣椒素之前，通过从细胞内钙库释放Ca2+（使用10毫摩尔咖啡因）来增加Ca2+会增加I(TRPV-1)（14.1±7%），而与对照相比，I(Ca(V))降低至51.6±4.9%。丹曲林（5微摩尔）在实验前部分减少钙库的Ca2+释放，导致I(TRPV-1)的作用不太明显[相对于I(Ca(V))峰值为24.5±8.8%]，在施加辣椒素后I(Ca(V))降低至基线的35.4±3%。
