Mitrofanis J
Department of Human Anatomy, University of Oxford, UK.
Eur J Neurosci. 1994 Dec 1;6(12):1864-82. doi: 10.1111/j.1460-9568.1994.tb00578.x.
This study examines the connections of the thalamic reticular and perireticular cell groups in developing ferrets. Small crystals of Dil (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) were implanted into either the dorsal thalamus or the cerebral cortex of aldehyde-fixed prenatal and postnatal ferret brains. A small implant of Dil into the presumptive lateral geniculate nucleus during early prenatal development [between embryonic day 23 (E23) and E25] reveals many retrogradely labelled cells in the reticular nucleus. At E40, just before birth, the number of cells retrogradely labelled in the reticular nucleus has become reduced compared to earlier prenatal implants, whether from small or large implants of Dil into the lateral geniculate nucleus. By postnatal day 7, an adult-like pattern of retrograde labelling is seen in the reticular nucleus; at this age, a small implant of Dil limited to the lateral geniculate nucleus retrogradely labels a discrete group of cells located in the caudal regions of the reticular nucleus. In the internal capsule, adjacent to the reticular nucleus, there are two distinct groups of neurons. One group, called the large-celled perireticular zone (LPR), enters the internal capsule very early in development (from E25; Mitrofanis, J., Eur. J. Neurosci., 6, 253-263, 1994) and is not labelled from the lateral geniculate nucleus at any developmental stage. Small implants of Dil into presumptive visual and somatosensory cortices shows that the LPR lies in a distinct region of the primordial internal capsule. Corticothalamic and thalamocortical axons turn sharply in the region of the LPR, whilst corticospinal and corticobulbar axons pass straight through the LPR on towards their more caudal targets. Later, after both sets of axons have reached their targets, the LPR is not seen in the internal capsule. The other group of cells in the internal capsule, called the small-celled perireticular zone (SPR), forms a distinct band of cells lying midway between the reticular nucleus and the globus pallidus. These cells enter the internal capsule much later in development, at about E40. Unlike the cells in the LPR, cells in the SPR are retrogradely labelled after an implant of Dil into the lateral geniculate nucleus, and there are many which remain in the adult (Clemence, A. E. and Mitrofanis, J., J. Comp. Neurol., 322, 167-181, 1992).
本研究探讨了发育中的雪貂丘脑网状核和网状周细胞群的联系。将Dil（1,1'-二辛基-3,3,3',3'-四甲基吲哚羰花青高氯酸盐）小晶体植入醛固定的产前和产后雪貂脑的背侧丘脑或大脑皮层。在产前早期发育阶段[胚胎第23天（E23）至E25]，将一小片Dil植入推测的外侧膝状体核，可在网状核中发现许多逆行标记的细胞。在E40，即出生前，与早期产前植入相比，无论将Dil小剂量还是大剂量植入外侧膝状体核，网状核中逆行标记的细胞数量都已减少。到出生后第7天，在网状核中可见到类似成年动物的逆行标记模式；在这个年龄，仅植入外侧膝状体核的一小片Dil可逆行标记位于网状核尾侧区域的一组离散细胞。在内囊，与网状核相邻，有两组不同的神经元。一组称为大细胞网状周带（LPR），在发育早期（从E25开始；米特罗法尼斯，J.，《欧洲神经科学杂志》，6，253 - 263，1994）就进入内囊，在任何发育阶段都不会被外侧膝状体核标记。将Dil小剂量植入推测的视觉和体感皮层显示，LPR位于原始内囊的一个独特区域。皮质丘脑和丘脑皮质轴突在LPR区域急剧转向，而皮质脊髓和皮质延髓轴突则直接穿过LPR向更靠尾侧的靶点延伸。后来，在两组轴突都到达靶点后，在内囊中就看不到LPR了。内囊中的另一组细胞称为小细胞网状周带（SPR），形成一条位于网状核和苍白球之间中间位置的独特细胞带。这些细胞在发育后期，大约在E40时才进入内囊。与LPR中的细胞不同，将Dil植入外侧膝状体核后，SPR中的细胞会被逆行标记，并且在成年动物中仍有许多细胞存在（克莱门斯，A. E.和米特罗法尼斯，J.，《比较神经学杂志》，322，167 - 181，1992）。
