Martin G F, Ho R H, Hazlett J C
Department of Anatomy and Neuroscience Program, Ohio State University College of Medicine, Columbus 43210.
Brain Res Dev Brain Res. 1989 Jun 1;47(2):161-70. doi: 10.1016/0165-3806(89)90172-7.
We have employed immunocytochemical and axonal transport techniques to study the development of major projections to the dorsal striatum of the North American opossum. The opossum is born in a very immature state, 12-13 days after conception, and climbs into an external pouch where it remains attached to a nipple for several months. Its immaturity at birth and its protracted postnatal development make the opossum a good model for developmental studies. Although tyrosine hydroxylase-like immunoreactive (TH-LI), presumably dopaminergic, neurons were present in the ventral mesencephalon at birth (the presumptive substantia nigra and ventral tegmental area), there was no evidence for TH-LI axons in the striatal anlage. By postnatal day (PD)6, a few immunostained axons were found within the putamen. The subsequent growth of TH-LI axons into the striatum followed general caudal to rostral and ventrolateral to dorsomedial gradients and, at any age, they were most numerous in the areas exhibiting the greatest cytodifferentiation. By estimated (E)PD45, TH-LI axons were present in most, if not all, areas of the striatum. Serotoninergic (5-HT)-LI axons were found lateral to the presumptive striatum at birth but not within it. By PD7, however, a few 5-HT-LI axons could be identified in the putamen. The growth of 5-HT-LI axons into the striatum generally followed the same gradients described for TH-LI axons although at all ages their density was much less. Using the orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), evidence was obtained for the existence of thalamostriatal projections by PD5 and for corticostriatal projections by PD10. Crossed corticostriatal projections were present by EPD23. Our results suggest that the development of major projections to the striatum occurs postnatally in the opossum, rather than prenatally as in placental animals. The timetable for striatal innervation is discussed in light of the developmental sequences established for other motor circuits.
我们运用免疫细胞化学和轴突运输技术来研究北美负鼠背侧纹状体主要投射的发育情况。负鼠在受孕12 - 13天后出生，处于非常不成熟的状态，会爬进体外育儿袋，在那里它会附着在乳头几个月。其出生时的不成熟以及出生后漫长的发育过程使负鼠成为发育研究的良好模型。尽管出生时（推测的黑质和腹侧被盖区）腹侧中脑存在酪氨酸羟化酶样免疫反应性（TH - LI）神经元，推测为多巴胺能神经元，但纹状体原基中没有TH - LI轴突的证据。到出生后第6天（PD6），在壳核内发现了一些免疫染色的轴突。随后TH - LI轴突向纹状体的生长遵循一般从尾侧向头侧以及从腹外侧向背内侧的梯度，并且在任何年龄，它们在细胞分化最显著的区域数量最多。到估计的出生后第45天（EPD45），TH - LI轴突存在于纹状体的大部分区域（如果不是全部区域的话）。5 - 羟色胺能（5 - HT） - LI轴突在出生时在推测的纹状体外侧被发现，但不在其内部。然而，到PD7时，在壳核中可以识别出一些5 - HT - LI轴突。5 - HT - LI轴突向纹状体的生长通常遵循与TH - LI轴突相同的梯度，尽管在所有年龄其密度都要小得多。利用与辣根过氧化物酶结合的小麦胚凝集素（WGA - HRP）的顺行运输，在PD5时获得了丘脑纹状体投射存在的证据，在PD10时获得了皮质纹状体投射存在的证据。交叉的皮质纹状体投射在EPD23时出现。我们的结果表明，负鼠纹状体主要投射的发育发生在出生后，而不是像胎盘动物那样在出生前。根据为其他运动回路建立的发育顺序讨论了纹状体神经支配的时间表。
