Distribution of cholinergic contacts on Renshaw cells in the rat spinal cord: a light microscopic study
Distribution of cholinergic contacts on Renshaw cells in the rat spinal cord: a light microscopic study
复制标题
DOI：
10.1111/j.1469-7793.1999.787ab.x
复制
发表时间：
1999-03-15
影响因子：
5.5
通讯作者：
Fyffe, REW
中科院分区：
文献类型：
--
作者：
Alvarez, FJ;Dewey, DE;Fyffe, REW
1.免疫组织化学方法显示大鼠脊髓胆碱能终末的囊泡型乙酰胆碱转运体(VAChT)。为了确定这些终末与Renshaw细胞的关系，我们用免疫组织化学双重标记的方法对Renshaw细胞进行免疫组织化学标记。腹角的vii。使用计算机辅助重建系统对总共50个伦肖细胞进行了定量分析，以提供接触部位的准确定位和体细胞和树突表面积的确定。在Calbindin D28k标记的Renshaw细胞胞体中可追踪到长达413微米的树突状突起，在Gen标记的细胞中可追踪到长达184微米的树突。在50个Renshaw细胞上共观察到3330个胆碱能终末，每个细胞有21-138个终末对位，平均每个细胞有66.6+/-25.56个接触。绝大多数(83.5%)的终末与树突相对，而不是胞体。胆碱能触点的总密度从胞体和近端树突起的25微米处略高于1个/100微米(2)增加到距离胞体50~250微米的树突表面的4~5个/100微米(2)。单个突触前纤维经常与单个Renshaw细胞的胞体和/或树突形成多个接触。针对Renshaw细胞的Vacht免疫反应终末直径从0.6~6.9微米不等(平均2.26+/-0.94；n=986)，平均小于与运动神经元相关的胆碱能C终末，但大于与其他腹角间神经元接触的Vacht免疫反应终末。Renshaw细胞上胆碱能终末密度高、体积较大，可能与运动神经元与Renshaw细胞之间存在较强的突触联系有关。事实上，大多数接触分布在树突上，这使得运动神经元轴突的侧支输入容易受到位于胞体和近端树突上的显著的甘氨酸能抑制性突触的抑制。兴奋性胆碱能突触和抑制性甘氨酸能突触的相对位置和结构特征可能解释了为什么伦肖细胞虽然能够在运动轴突后以很高的频率放电，但在运动活动中的放电频率似乎相对较低。
1. Cholinergic terminals in the rat spinal cord were revealed by immunohistochemical detection of the vesicular acetycholine transporter (VAChT). In order to determine the relationships of these terminals to Renshaw cells, we used dual immunolabelling with antibodies against gephyrin or calbindin D28k to provide immunohistochemical identification of Renshaw cells in lamina. VII of the ventral horn.2. A total of 50 Renshaw cells were analysed quantitatively using a computer-aided reconstruction system to provide accurate localization of contact sites and determination of somatic and dendritic surface area. Dendrites could be traced for up to 413 mu m from the soma in calbindin D28k-identified Renshaw cells and up to 184 mu m in gephyrin-identified cells.3. A total of 3330 cholinergic terminals were observed on 50 Renshaw cells, with a range of 21-138 terminal appositions per cell (mean 66.6 +/- 25.56 contacts per cell). The vast majority (83.5%) of the terminals were apposed to dendrites rather than the soma. The overall density of cholinergic contacts increased from a little above 1 per 100 mu m(2) on the soma and initial 25 mu m of proximal dendrites to 4-5 per 100 mu m(2) on the surface of dendritic segments located 50-250 mu m from the soma. Single presynaptic fibres frequently formed multiple contacts with the soma and/or dendrites of individual Renshaw cells.4. VAChT-immunoreactive terminals apposed to Renshaw cells varied in size from 0.6 to 6.9 mu m in diameter (mean 2.26 +/- 0 94; n. = 986) and were on average smaller than the cholinergic C-terminals apposed to motoneurones, but larger than VAChT-immunoreactive terminals contacting other ventral horn interneurones.5. The high density and relatively large size of many cholinergic terminals on Renshaw cells presumably correlates with the strong synaptic connection between motoneurones and Renshaw cella. The fact, that the majority of contacts are distributed over the dendrites makes the motoneurone axon collateral input susceptible to inhibition by the prominent glycinergic inhibitory synapses located on the soma and proximal dendrites. The relative positions and structural features of the excitatory cholinergic and inhibitory glycinergic synapses may explain why Renshaw cells, although capable of firing at very high frequency following motor axon stimulation, appear to fire at relatively low rates during locomotor activity.