P物质对大鼠三叉神经节神经元H＋-门控电流的调制

Modulation of proton-gated current by substance P in trigeminal ganglion neurons of rat

目的探讨P物质（sP）对大鼠三叉神经节（TG）神经元膜H＋-门控电流的调制作用及其机制。方法急性分离TG神经元，通过排管快速换液装置行胞外给药，电极内灌药行胞内透析后，采用全细胞膜片钳技术记录神经元膜H＋-门控电流。结果依照我们在背根神经节（DRG）神经元分类的方式，同样可将TG神经元H＋-门控电流也分为四型，即T-型、S-型、B-型、O-型：共加sP和H＋能浓度依赖性增强S-型H＋-门控电流，SP受体拮抗剂GR82334不能阻断此作用：共加SP和H＋能增强B-型H＋-门控电流，GR82334和胞内透析GDP—B—S能阻断SP对B．型H＋-门控电流的这一增强作用，而预加sP则抑制B-型HL门控电流，并以短暂成分尤为明显，此抑制效应不能被GR82334阻断。结论SP对H＋-门控电流的调制依ASIC亚基组成不同，其作用机制有所不同；S-型H＋-门控电流的ASIC分子膜外结构上可能存在SP的别构位点。

Objective To investigate the modulatory effect of substance P （SP） on proton-gated current in the membrane of rat trigeminal ganglion （TG） neurons and its underlying mechanism. Methods Neurons were isolated mechanically and enzymatically from TG of rat. Whole-cell patch clamp technique was used for recording the proton-gated current in freshly isolated neurons. Results Proton-gated currents recorded from rat TG neurons could be classified into 4 distinct types： T-type, S-type, B-type and O-type in the present study. Co-application of SP and proton potentiated S-type proton-gated currents in a concentration-dependent manner, and the potentiation was not blocked by SP receptor antagonist, GR82334; co-application of SP and proton potentiated B-type proton-gated currents, and GR82334 and intracellular dialysis of GDP-β-S blocked the potentiation of SP. Pre-application of SP inhibited B-type proton-gated current, especially the transient component. The inhibition could not be reversed by pretreatment with GR82334. Conclusions The mechanisms of modulation of proton-gated current by SP is associated with the difference of their makeup of subunits of acid-sensing ion channels （ASICs）, and there may be an allosteric position of SP in the outside framework of ASICs in neuronal membrane.