5-HT_2受体介导大鼠DRG神经元膜GABA 激活电流的增强作用(英文)

5-HT_2 receptor mediated the potentiation of GABA-activated current in the membrane of the dorsal root ganglion neurons of rat

目的 探讨 5 HT对大鼠DRG神经元膜GABA 激活电流的调节作用及其机制。方法 在新鲜分离的大鼠DRG神经元标本上,以全细胞膜片钳技术记录膜电流,用排管快速换液装置行胞外给药,以胞内透析技术分析信号转导途径。结果 给予GABA可使多数受检细胞产生浓度依赖性内向电流 (IGABA)。预加 5 HT,可使IGABA增加。此效应可被 5 HT2受体特异性激动剂α methyl 5 HT( 1×10-6mol·L-1 )所模拟,被 5 HT2受体选择性拮抗剂cyproheptadine所阻断。在部分细胞, 5 HT本身可引起由 5 HT3受体介导的快速内向电流,但并未发现该电流与 5 HT对IGABA的增强作用有必然的联系。从GABA激活电流的量效曲线可见,预加 5 HT后和对照曲线相比,阈浓度不变、EC50值相近,IGABA最大值增加 33. 6%。胞内透析GDP β S或H 7可取消 5 HT增强IGABA的效应,而透析H 9无效。结论 5 HT可增强GABA 激活电流,其机制为 5 HT2受体激活后通过PKC引起GABAA受体胞内磷酸化所致。

Aim To explore the modulation of 5-HT on GABA-activated current (I GABA) in the membrane of rat dorsal root ganglion (DRG) neurons and its mechanism. Methods Rat DRG neurons were isolated mechanically and enzymatically, on which whole-cell patch clamp recording and repatch technique for intracellular dialysis were performed. Results In the majority of neurons examined (92.0%, 69/75) GABA induced a concentration-dependent inward current. In neurons sensitive to GABA preapplication of 5-HT produced potentiation effect (82.6%, 57/69) on I GABA. Preapplication of 5-HT at concentrations of 1×10 -6, 1×10 -5, 1×10 -4 and 1×10 -3 mol·L -1 potentiated I GABA by ( 35±8)% (n=8), (47±11)% (n=10), (65±17)% (n=9) and (75±18)% (n=11), respectively. This effect was mimicked by α-methyl-5-HT (1×10 -6 mol·L -1), a specific 5-HT 2 receptor agonist, and reversed by cyproheptadine, a selective 5-HT 2 receptor antagonist. The potentiation of I GABA by 5-HT was irrespective to whether the I 5-HT presents or not in a subset of neurons. The concentration-response curves for GABA before and after pretreatment with 5-HT manifested the same threshold value and similar EC 50 (2.0×10 -5 and 1.9×10 -5 mol·L -1, respectively), while the maximal value of I GABA for the latter was 33.6% higher than that for the former. Intracellular dialysis with GDP-β-S or H-7 abolished the potentiation of I GABA by 5-HT, while H-9 did not. Conclusion 5-HT can potentiate GABA-activated current via PKC-dependent phosphorylation of GABA A receptor following the activation of 5-HT 2 receptor.