P物质对大鼠DRG神经元H+门控电流的调制作用

 目的：观察P物质（SP）对神经元H+门控电流的调制作用及其可能存在的机制。方法：采用全细胞膜片钳技术分别记录pH 4.0、pH 5.0、pH 6.0及共加H+ 与SP情况下，急性分离的大鼠背根神经节（DRG)神经元H+门控电流的形式。通过胞内透析技术分析SP对H+门控电流可能的调控机制。结果：H+门控电流可划分为短暂内流型（T型）、持续内向电流型（S型）、反向电流型（O型）及双相内向电流型（B型）。SP对S型和B型中持续成分的H+门控电流有明显增强作用，这种电流幅值增强达（85.53±22.93）%，约81.8%细胞的这种增强效应不能被选择性的SP受体NK1拮抗剂阻断，而非肽类的SP受体NK1拮抗剂对约75%的DRG神经元可明显阻断这种增强效应;SP对S型和B型中持续成分的H+门控电流也有明显抑制作用,抑制的幅值达（48.46±4.45）%，并且约88.9%细胞的这种抑制效应不能被SP受体NK1拮抗剂所阻断。通过胞内透析技术在细胞内液中加入GDP-β-S后不能消除SP对H+门控电流的调制作用。结论：H+门控电流有T型、S型、O型及B型4种电流类型。SP对H+门控电流有增强和抑制的双向调节作用。SP可能通过G蛋白偶联受体通路及与H+门控离子通道的某一位点直接结合来发挥对H+门控电流的双向调节调制作用。

Modulating action of substance P on H+-gated current in rat dorsal root ganglion neurons

AIM：To investigate the effects of substance P (SP) on the modulation of H+-gated current in neurons. METHODS：Whole-cell patch-clamp technique was used to record the H+-gated current in the acutely isolated rat dorsal root ganglion (DRG) neurons at pH 4.0, pH 5.0, pH 6.0, and both SP and H+. The modulating action of SP on H+-gated current in the acutely isolated rat DRG neurons was studied by intracellular dialysis. RESULTS：H+-gated currents recorded at pH 5.0 were divided into 4 types: transient inward (T-type),sustained inward (S-type),biphasic inward (B-type) and opposite (O-type). SP exhibited obvious enhancing effect on the sustained component of S-type and B-type  H+-gated currents, and the enhancing current amplitude was (85.53±22.93)%. However, the enhancing effect was not blocked by the SP receptor NK1 antagonist in about 81.8% DRG neurons. The enhancing effect was blocked by nonpeptidic SP receptor antagonist in about 75% DRG neurons. SP also exhibited obvious inhibitory effect on the sustained component of S-type and B-type H+-gated currents, and the inhibitory current amplitude was (48.46±4.45)%. However, the inhibitory effect was not blocked by the SP receptor antagonist in about 88.9% DRG neurons. After intracellular dialysis, GDP-β-S could not block the modulating action of SP on H+-gated currents. CONCLUSION：There are 4 types of H+-gated currents in acutely isolated rat DRG neurons: T-type, S-type, B-type and O-type. The modulating action of SP on H+-gated current exhibits both enhancement and inhibition. The regulatory mechanism includes G-protein-coupled receptor pathway and the binding of SP to a locus of H+-gated ion channels to exert modulating action on the H+-gated current.