van Raamsdonk W, Smit-Onel M J, Maslam S, Velzing E, de Heus R
Department of Experimental Zoology, University of Amsterdam, The Netherlands.
Acta Histochem. 1998 Apr;100(2):133-48. doi: 10.1016/S0065-1281(98)80022-6.
Effects of spinal cord transection on the synaptology of zebrafish spinal motoneurons were studied. The transection was made at the level of the 14th vertebra and the synaptology of motoneuron somata and dendrites was analysed at the level of the 21st to the 23rd vertebrae at one month and three months after transection. Horseradish peroxidase, applied to the myotomal muscle, was used to label motoneuron somata and dendritic branches in central and in lateral areas of the neuropil (referred to as central and lateral dendritic profiles). Boutons impinging on motoneurons were classified according to the morphology of the vesicles. We discerned R-boutons with spherical vesicles, F-boutons with flat vesicles and DC-boutons with at least one dense core vesicle. The apposition lengths of R-, F- and DC-boutons and the circumference of labelled profiles were determined to assess the proportional covering of boutons on somata and dendrites. Ratio's of covering with R- and F-boutons (R/F ratio) for somata, central and lateral dendritic profiles were 1.1, 2.1, and 2.1 in control fish and 0.5, 0.5 and 0.9 in lesioned fish at one month after transection, respectively. The total covering of motoneurons in lesioned fish was decreased by 20% on somata and by 30% on lateral dendritic profiles, whereas central dendritic profiles did not change significantly. At three months after transection the R/F ratio's for somata, central and lateral dendritic profiles were 0.5, 0.7 and 0.6, respectively. The total covering on somata and central and lateral dendritic profiles was at control levels. The anatomical aspects of the changes in synaptology indicate that in control fish 50 to 60% of the R-boutons on the motoneuron surface originate from descending axons. In contrast, almost all F-boutons seem to be from local origin.
研究了脊髓横断对斑马鱼脊髓运动神经元突触学的影响。横断在第14节椎骨水平进行，在横断后1个月和3个月，对第21至23节椎骨水平的运动神经元胞体和树突的突触学进行分析。将辣根过氧化物酶应用于肌节肌肉，用于标记神经毡中央和外侧区域（称为中央和外侧树突轮廓）的运动神经元胞体和树突分支。根据囊泡的形态对与运动神经元接触的终扣进行分类。我们识别出具有球形囊泡的R终扣、具有扁平囊泡的F终扣和具有至少一个致密核心囊泡的DC终扣。测定R终扣、F终扣和DC终扣的贴附长度以及标记轮廓的周长，以评估终扣在胞体和树突上的比例覆盖情况。在横断后1个月，对照鱼的胞体、中央和外侧树突轮廓的R终扣与F终扣覆盖比例（R/F比例）分别为1.1、2.1和2.1，而损伤鱼分别为0.5、0.5和0.9。损伤鱼运动神经元的总覆盖在胞体上减少了20%，在外侧树突轮廓上减少了30%，而中央树突轮廓没有显著变化。在横断后3个月，胞体、中央和外侧树突轮廓的R/F比例分别为0.5、0.7和0.6。胞体、中央和外侧树突轮廓的总覆盖处于对照水平。突触学变化的解剖学方面表明，在对照鱼中，运动神经元表面50%至60%的R终扣起源于下行轴突。相比之下，几乎所有F终扣似乎都来自局部起源。
