目的　观察大鼠延髓背角 (MDH)Ⅲ层深部内绿色荧光蛋白 (GFP)基因重组病毒标记神经元的形态学特点。　方法　将GFP基因重组病毒注入Ⅲ层深部后感染并标记神经元 ,标记结果用免疫组织化学染色显示 ,重塑后观察神经元形态。　结果　在远离注射区的MDHⅢ层深部可见少量单个GFP标记的神经元。根据GFP标记神经元的形态学特征 ,尤其是其轴突及其分支的特点 ,可将标记神经元分为投射神经元和中间神经元。投射神经元的轴突分支向Ⅲ层浅部、Ⅱ层和 或延髓网状结构延伸。中间神经元的轴突分支较密集且主要集中于Ⅲ层。　结论　根据GFP标记神经元的轴突及其分支特点 ,可将MDHⅢ层深部的神经元分为投射神经元和中间神经元 ;GFP基因重组病毒标记技术是研究神经元形态的有效手段 Objective To observe the morphological characteristics of green fluorescent protein (GFP) gene-tagged neurons in deep layer Ⅲ of medullary dorsal horn (MDH) in rats. Methods The GFP recombinant virus was injected into the deep layer Ⅲ and infected and labeled neurons. The results of immunohistochemical staining showed that the morphology of neurons was observed after remodeling. Results A small number of single GFP-labeled neurons were observed in the deep layers of MDH far away from the injection site. According to the morphological characteristics of GFP labeled neurons, especially their axons and their branches, the labeled neurons can be divided into projection neurons and intermediate neurons. The axon branches of the projecting neurons extend to the superficial layer III, layer II and / or medulla oblongata. The axons in the interneurons are more dense and mainly focus on the third layer. Conclusion According to the characteristics of axon and branch of GFP-labeled neurons, the neurons in the deep layer of MDH can be divided into projectile neurons and interneurons. The recombinant GFP-tagged viral marker is an effective method to study neuronal morphology