The inhibitory effect of α-methyl-5-HT on ATP-activated currents in rat dorsal root ganglion neurons

Abstract The purpose of this study was to explore the inhibitory effect of α-methyl-5- hydroxytryptamine (α-methyl-5-HT) on ATP-activated current (IATP) in rat dorsal root ganglion (DRG) neurons. Whole-cell patch clamp experiment was performed on cultured rat DRG neurons. One minute after treatment with α-methyl-5-HT, ATP (10-4 mol/L) activation current in rat DRG neurons was inhibited. However, this inhibitory effect was independent of the current caused by α-methyl-5-HT. The dose-response curve for IATP showed that α-methyl-5-HT significantly shifted it. The Kd values of ATP-activated currents before and after the pre-addition of α-methyl-5-HT were similar (4.23×10-5 mol/L vs. 6.81×10-5 mol/L). Furthermore, cyproheptadine (10-6 mol/L), an antagonist of 5-HT2 receptor, can reverse the inhibition of α-methyl-5-HT. After intracellular dialysis of KN93 (CaMKII inhibitor) and H7 (PKC inhibitor), this inhibition was also completely eliminated. In conclusion, our results showed that α-methyl-5-HT inhibited ATP-activated current through activating the 5-HT2 receptor and resulting in phosphorylation of the ATP receptor. It was caused by the activation of G protein coupled receptor and corresponding intracellular signaling transduction cascade.

摘要 本研究旨在探讨α-甲基-5-羟色胺（α-methyl-5-HT）对大鼠背根神经节（DRG）神经元中ATP激活电流（IATP）的抑制作用。实验对培养的大鼠DRG神经元开展全细胞膜片钳记录。经α-甲基-5-HT处理1分钟后，大鼠DRG神经元的ATP（10^-4 mol/L）激活电流受到显著抑制。但该抑制效应与α-甲基-5-HT自身诱导产生的电流无关。ATP激活电流的剂量-反应曲线结果显示，α-甲基-5-HT可使曲线显著右移。预先给予α-甲基-5-HT前后，ATP激活电流的Kd值相近（4.23×10^-5 mol/L 与 6.81×10^-5 mol/L）。进一步实验发现，5-羟色胺2型受体（5-HT2受体）拮抗剂赛庚啶（10^-6 mol/L）可逆转α-甲基-5-HT的抑制作用。在通过细胞内透析给予Ca²⁺/钙调蛋白依赖性蛋白激酶II（CaMKII）抑制剂KN93及蛋白激酶C（PKC）抑制剂H7后，该抑制效应也被完全消除。综上，本研究结果表明，α-甲基-5-HT通过激活5-HT2受体，引发ATP受体的磷酸化，从而抑制ATP激活电流，该过程由G蛋白偶联受体激活及下游细胞内信号转导级联反应介导。