小鼠脊髓内存在抑制性含锌神经元

EXISTENCE OF INHIBITORY ZINC-CONTAINING NEURONS IN MOUSE SPINAL CORD

目的探讨小鼠脊髓中是否含有抑制性的含锌神经元。方法应用锌金属自显影技术、免疫电镜技术和共聚焦激光扫描显微术,研究游离锌离子、锌转运蛋白(zinc transporter 3,ZnT3)与(glutamic acid decarboxylate,GAD)在小鼠脊髓内的共存情况。结果小鼠脊髓内至少有三种含锌神经元轴突终末,其中大多数为GAD阳性即γ-氨基丁酸能含锌神经元轴突终末,另外两种分别为GAD阴性含扁圆形小泡的甘氨酸能含锌神经元轴突终末和含圆形清亮小泡的兴奋性谷氨酸能含锌神经元轴突终末。结论在哺乳动物脊髓内存在大量的抑制性含锌神经元。锌离子从抑制性含锌神经元轴突终末释放到突触间隙内,作为神经调质作用于突触后的GABA受体或甘氨酸受体,参与脊髓运动和感觉功能的调控。

Objective To explore the existence of zinc-containing neurons in the mouse spinal cord. Methods Autometallography, immuno-electron microscopy and confoeal laser scanning microscopy were used to investigate the colocalization of zinc ion, zinc transporter ZnT3 and glutarnic acid decarboxylate （GAD）. Results At least three types of zinc-containing neurons could be observed in the mouse spinal cord. The majority of zinc-containing terminals were GAD positive GABAergic terminals. The other two types of zinc-containing terminals were GAD negative inhibitory glycinergic terminals with flat vesicles, and excitatory glutaminergic terminals with round clear vesicles. Conclusion Most of the zinc-containing terminals in the mouse spinal cord are inhibitory. Zinc ions are released into the synaptic cleft. In the extracellular fluid, zinc interacts with postsynaptic GABA receptors or glycine receptors, and plays a role as a neuromodulator. Finally, zinc is involved in both motor and sensory processing at the spinal cord level.