Naumann T, Kermer P, Frotscher M
Institute of Anatomy, University of Freiburg, Germany.
J Comp Neurol. 1994 Dec 8;350(2):161-70. doi: 10.1002/cne.903500202.
Most cholinergic projection neurons in the medial septal nucleus (MS) lose their capability to synthesize choline acetyltransferase (ChAT) after axotomy by bilateral fimbria-fornix transection. We have recently shown that identified septohippocampal neurons survive axotomy up to 10 weeks and display fine-structural characteristics of cells in control rats. However, the fate and functional role of these neurons remained unclear. Here we describe observations made in rats which survived axotomy for 6 months. Adult Sprague-Dawley rats were subjected to bilateral transection of the fimbria-fornix system. In some animals septohippocampal projection neurons were labeled by the retrograde fluorescent tracer Fluoro-Gold (FG) prior to axotomy. After varying survival times following fimbria-fornix transection, the animals were fixed and sections of the septal region immunostained for ChAT. Three weeks postlesion, the number of ChAT-positive cells in the MS was reduced to 19% of control, suggesting a severe neuronal loss. However, 10 weeks and 6 months after axotomy this value increased to 28% and 54%, respectively. Fine-structural analysis of ChAT-positive neurons after 6 months survival revealed all characteristics of vital cells including normal input synapses. The majority of these cells could be identified as former septohippocampal projection neurons by the presence of FG. We conclude that many neurons in the MS have the capacity to restore their transmitter synthesis in a long-lasting process following axotomy.
内侧隔核（MS）中的大多数胆碱能投射神经元在双侧穹窿-海马伞横断切断轴突后失去合成胆碱乙酰转移酶（ChAT）的能力。我们最近发现，已确定的隔-海马神经元在轴突切断后可存活长达10周，并表现出与对照大鼠细胞相似的精细结构特征。然而，这些神经元的命运和功能作用仍不清楚。在此，我们描述了对轴突切断后存活6个月的大鼠的观察结果。成年Sprague-Dawley大鼠接受双侧穹窿-海马伞系统横断。在一些动物中，在轴突切断前用逆行荧光示踪剂氟金（FG）标记隔-海马投射神经元。在穹窿-海马伞横断后的不同存活时间后，将动物处死并对隔区切片进行ChAT免疫染色。损伤后3周，MS中ChAT阳性细胞的数量减少至对照的19%，表明神经元严重丢失。然而，轴突切断后10周和6个月，该值分别增加到28%和54%。对存活6个月后的ChAT阳性神经元进行的精细结构分析揭示了活细胞的所有特征，包括正常的输入突触。通过FG的存在，这些细胞中的大多数可被鉴定为以前的隔-海马投射神经元。我们得出结论，MS中的许多神经元在轴突切断后的长期过程中具有恢复其递质合成的能力。
