Bjaalie J G, Brodal P
Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Norway.
Neurosci Res. 1997 Mar;27(3):199-210. doi: 10.1016/s0168-0102(96)01149-2.
We have studied the convergence and divergence in the pontocerebellar pathway. Two or three different fluorescent tracers were injected in separate folia of the parafloccular complex. Retrogradely labelled cells were quantitatively recorded. The estimated total number of labelled neurones in the pontine nuclei contralateral to the injection sites was 18000 (median; range 5000-46000; 14 cell populations, six animals). Using stereological principles, the total number of neurones on one side in the pontine nuclei was estimated to be 490000 (mean; n = 6). Thus, approximately 4% of the total number of neurones in the pontine nuclei would project to a single parafloccular folium. Assuming that the highest estimates of labelled cells are the most representative, the proportion would be 9%. Considering that the volume injected makes up a tiny fraction of the total cerebellar cortical volume, these figures reflect an extreme convergence. After injections in adjacent folia we observed 19-27% double labelling. The double labelling frequency dropped steeply with increasing distance between injections. The strong convergence and limited local axonal branching suggest the existence of extensive branching to widely separated cerebellar regions.
我们研究了脑桥小脑通路的汇聚和发散情况。将两到三种不同的荧光示踪剂分别注射到旁绒球复合体的不同小叶中。对逆行标记的细胞进行了定量记录。注射部位对侧脑桥核中标记神经元的估计总数为18000个（中位数；范围5000 - 46000个；14个细胞群，6只动物）。根据立体学原理，估计脑桥核一侧神经元的总数为490000个（平均值；n = 6）。因此，脑桥核中约4%的神经元会投射到单个旁绒球小叶。假设标记细胞的最高估计值最具代表性，该比例将为9%。考虑到注射的体积仅占小脑皮质总体积的极小部分，这些数字反映了极端的汇聚情况。在相邻小叶注射后，我们观察到19 - 27%的双重标记。双重标记频率随着注射部位之间距离的增加而急剧下降。强烈的汇聚和有限的局部轴突分支表明存在广泛分支至广泛分离的小脑区域。
