Banfro F T, Mize R R
Department of Anatomy, Louisiana State University Medical Center, New Orleans 70112, USA.
Brain Res. 1996 Sep 16;733(2):273-83. doi: 10.1016/0006-8993(96)00563-x.
Projection neurons from the superior colliculus (SC) to the cuneiform region (CFR) of the midbrain form distinct cell clusters in the intermediate gray layer which precisely overlap the cholinergic fiber patches in this region of the cat SC (Jeon and Mize, J. Comp. Neurol., 337 (1993) 127-150). The acetylcholine (ACh)-containing fiber patches do not express ACh until after birth. It is not known when the cell clusters first appear. In this study, we examined the development of the clusters by retrogradely labeling the cells with a tracer injected into the CFR. Kittens aged from embryonic day E34 to E57 and postnatal day P1 to P14 were perfused with aldehyde fixatives and crystals of the carbocyanine dye DiI were placed into the CFR. After 5- to 8-week incubations, the SC was sectioned and examined using epi-fluorescent microscopy. At E34, very few labeled cells and fibers were present in SC. Between E41 and E46, both labeled cells and fibers were found within the intermediate gray (IGL) and deep gray (DGL) layers of SC. In one E46 case, a few labeled cells were grouped together within the IGL, suggesting the onset of clusters seen at later ages. By E51, DiI labeling produced an obvious pattern of clustered cells. Up to 4 clusters were seen in a single section, each containing 4-12 labeled neurons. By E57, labeled cell clusters were conspicuous in the IGL in caudal sections and the number of cells per cluster was increased. This pattern was also present at birth (P1). Scattered labeled neurons were also found outside the clusters and throughout the deep layers as were fibers innervating this region of SC. In summary, the axonal projections of the IGL clustered cells appear to reach the cuneiform region as early as E46 and are well-developed by E57. The clustering of efferent neurons precedes the formation of cholinergic fiber patches in the cat SC which is first identifiable using ChAT antibodies around the second postnatal week of life.
从中脑上丘（SC）投射到中脑楔形区（CFR）的投射神经元，在中间灰质层形成不同的细胞簇，这些细胞簇与猫SC该区域的胆碱能纤维斑精确重叠（Jeon和Mize，《比较神经学杂志》，337（1993）127 - 150）。含乙酰胆碱（ACh）的纤维斑在出生后才表达ACh。细胞簇首次出现的时间尚不清楚。在本研究中，我们通过向CFR注射示踪剂逆行标记细胞，来研究这些细胞簇的发育情况。对胚胎期E34至E57以及出生后第1天至第14天的小猫灌注醛类固定剂，并将羰花青染料DiI的晶体置于CFR中。经过5至8周的孵育后，对SC进行切片并使用落射荧光显微镜检查。在E34时，SC中存在极少的标记细胞和纤维。在E41至E46之间，在SC的中间灰质（IGL）层和深灰质（DGL）层中均发现了标记细胞和纤维。在一个E46的样本中，一些标记细胞在IGL内聚集在一起，提示在较晚年龄出现的细胞簇开始形成。到E51时，DiI标记产生了明显的细胞簇模式。在单个切片中可看到多达4个细胞簇，每个簇包含4 - 12个标记神经元。到E57时，在尾侧切片的IGL中标记细胞簇很明显，且每个簇中的细胞数量增加。这种模式在出生时（P1）也存在。在细胞簇之外以及整个深层中也发现了散在的标记神经元，还有支配SC该区域的纤维。总之，IGL簇状细胞的轴突投射最早在E46时似乎就到达了楔形区，到E57时已发育良好。在猫的SC中，传出神经元的聚集先于胆碱能纤维斑的形成，胆碱能纤维斑最早在出生后第二周左右可通过ChAT抗体识别。
