Nikkhah G, Cunningham M G, Cenci M A, McKay R D, Björklund A
Department of Medical Cell Research, University of Lund, Sweden.
J Neurosci. 1995 May;15(5 Pt 1):3548-61. doi: 10.1523/JNEUROSCI.15-05-03548.1995.
Reconstruction of the nigrostriatal pathway by long axon growth derived from dopamine-rich ventral mesencephalic (VM) transplants grafted into the substantia nigra may enhance their functional integration as compared to VM grafts implanted ectopically into the striatum. Here we report on a novel approach by which fetal VM grafts are implanted unilaterally into the substantia nigra (SN) of 6-hydroxydopamine (6-OHDA)-lesioned neonatal pups at postnatal day 3 (P3) using a microtransplantation technique. The results demonstrate that homotopically placed dopaminergic neurons survive and integrate well into the previously 6-OHDA-lesioned neonatal SN region. Moreover, the tyrosine hydroxylase (TH)-positive neurons extended axons rostrally along the white matter tract of the internal capsule closely following the course of the original nigrostriatal pathway. The graft reestablished a TH-positive axon terminal network in the ipsilateral caudate-putamen, with the highest density in the medial and central parts. Retrograde labeling with Fluoro-Gold from the host striatum demonstrated that most of the transplant neurons giving rise to the graft-derived fiber outgrowth were TH-positive, but revealed also a small proportion of projecting neurons which were TH-negative. Amphetamine-induced striatal Fos expression was normalized in the caudate-putamen ipsilateral to the intranigral VM grafts, showing hyperexpression in some areas of the striatum, and the apomorphine-induced Fos expression seen in the 6-OHDA-lesioned animals was completely reversed on the grafted side. These findings indicate that the graft-derived dopaminergic reinnervation of the striatum is functional. The microtransplantation strategy may provide new avenues for the exploration of morphological and functional integration of fetal dopamine neurons in the nigrostriatal system and give new insights into the mechanisms controlling long-distance axon growth in the brain.
与异位植入纹状体的腹侧中脑（VM）移植相比，将富含多巴胺的VM移植到黑质，通过长轴突生长重建黑质纹状体通路，可能会增强其功能整合。在此，我们报告一种新方法，即使用微移植技术，在出生后第3天（P3）将胎儿VM移植单侧植入6-羟基多巴胺（6-OHDA）损伤的新生幼崽的黑质（SN）。结果表明，同位放置的多巴胺能神经元存活并很好地整合到先前6-OHDA损伤的新生SN区域。此外，酪氨酸羟化酶（TH）阳性神经元沿着内囊的白质束向头端延伸轴突，紧密跟随原始黑质纹状体通路的行程。移植在同侧尾状核-壳核重新建立了TH阳性轴突终末网络，在内侧和中央部分密度最高。用Fluoro-Gold从宿主纹状体进行逆行标记表明，产生移植衍生纤维生长的大多数移植神经元是TH阳性的，但也显示出一小部分投射神经元是TH阴性的。安非他明诱导的纹状体Fos表达在黑质内VM移植同侧的尾状核-壳核中恢复正常，在纹状体的某些区域显示过度表达，并且在6-OHDA损伤动物中看到的阿扑吗啡诱导的Fos表达在移植侧完全逆转。这些发现表明，移植衍生的纹状体多巴胺能再支配是有功能的。微移植策略可能为探索胎儿多巴胺能神经元在黑质纹状体系统中的形态和功能整合提供新途径，并为控制大脑中长距离轴突生长的机制提供新见解。
