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目的研究α1-肾上腺素受体(α1-AR)调控脊髓背角感觉神经元谷氨酸能突触传递的作用机制。方法在急性切取的腰段脊髓切片上,利用全细胞膜片钳法记录α1-AR激动剂苯肾上腺素对脊髓背角浅层神经元抑制性和兴奋性突触后电流(IPSCs和eEPSCs)的影响。结果苯肾上腺素对IPSCs频率产生剂量依赖性兴奋作用,此作用可被α1-AR特异性拮抗剂WB4101完全拮抗。苯肾上腺素对eEPSCs振幅的抑制作用可以部分被GABAA受体拮抗剂印防己毒素(picrotoxin,PTX)拮抗。结论位于脊髓背角神经元的α1-AR,促进初级传入纤维在脊髓背角释放γ-氨基丁酸(GABA),进而主要通过GABAA受体抑制初级传入纤维兴奋性谷氨酸能神经冲动的传入。下行肾上腺素能系统可能通过GABAA受体机制参与突触前对谷氨酸递质释放的调节作用。
Objective To investigate the mechanism of α1-adrenergic receptor (α1-AR) regulating glutamate synaptic transmission in sensory neurons of spinal dorsal horn. Methods Whole-cell patch-clamp technique was used to record the effect of phenylephrine, an α-AR agonist, on the inhibitory and excitatory postsynaptic currents (IPSCs and ePSCs) of the spinal dorsal horn neurons in acutely transected lumbar spinal cord slices . Results Phenylephrine had a dose-dependent and excitatory effect on the frequency of IPSCs. This effect was completely antagonized by the α1-AR specific antagonist WB4101. The inhibitory effect of phenylephrine on the amplitude of eEPSCs can be partially antagonized by the GABAA receptor antagonist picrotoxin (PTX). Conclusion α1-AR, located in the dorsal horn of spinal cord, promotes the release of γ-aminobutyric acid (GABA) by primary afferent fibers in the dorsal horn of the spinal cord and thus inhibits primary afferent glutamatergic impulses of primary afferent fibers via the GABAA receptor The incoming. Down-regulation of adrenergic system may participate in presynaptic modulation of glutamate neurotransmitter release through the GABAA receptor mechanism.