α1-肾上腺素受体通过GABA_B受体调控脊髓背角神经元谷氨酸能突触传递

The role of α_1-adrenoceptors on glutamatergic synapse via GABA_B receptors in spinal dorsal horn

目的研究下行去甲肾上腺素系统α1-肾上腺素受体通过GABAB受体调控脊髓背角感觉神经元谷氨酸能突触传递的机制。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-肾上腺素受体激动剂苯肾上腺素刺激诱发的脊髓背角浅层神经元谷氨酸能兴奋性突触后电流(eEPSCs),给予GABAB受体特异性拮抗剂CGP55845,进一步观察GABAB受体在苯肾上腺素对突触终末eEPSCs调节过程中的作用。结果苯肾上腺素显著降低初级传入末梢单突触和多突触eEPSCs幅度,在突触后GABAB受体被从胞内阻断的条件下,再灌流CGP55845,阻断谷氨酸能突触前GABAB受体,可部分拮抗苯肾上腺素对刺激引发的EPSCs(eEPSCs)幅度的抑制作用。结论位于脊髓背角神经元α1-肾上腺素受体,通过GABAB受体抑制初级传入纤维兴奋性谷氨酸能神经冲动的传入,这种突触前对谷氨酸释放的调节可能是下行肾上腺素能系统对伤害性刺激调控的作用机制。

Objective To investigate the role of a1-adrenoceptors on glutamatergic synapse via GABAB receptors in spinal dorsal horn. Methods Using whole-cell voltage-clamp recordings on acute spinal cord slice,effect of blockade of a1-adrcnoeeptors on glutamatergic synaptic transmission was studied. Results Selective al-adrenoceptors agonist phenylephrine significantly reduced the amplitude of monosynaptic and polysynaptic EPSCs evoked from primary afferents. The inhibitory effect of phenylephfine on evoked monosynaptic and polysynaptic glutamatergic EPSCs was largely blocked by the GABAB receptor antagonist CGP55845. Conclusion Activation of a1- adrenoeeptors in the spinal cord attenuates glutamatergie input from primary afferents mainly through GABAB receptors, indicating a presynaptie inhibition in the spinal cord may be involved in the regulation of nociception by the descending noradrenergie system.