Woolf T B, Shepherd G M, Greer C A
Section of Neuroanatomy, Yale University School of Medicine, New Haven, Connecticut 06510.
Synapse. 1991 Mar;7(3):181-92. doi: 10.1002/syn.890070303.
The morphology of olfactory bulb granule cell spines and their dendrodendritic synaptic relations with mitral and tufted cell dendrites were examined using serial electron micrographs and 3D computer reconstructions. Most granule cell spines were pedunculated with large elliptical heads and necks (stems) longer than those described for exclusively postsynaptic spines elsewhere in the nervous system. The spines typically contained a mitochondrion, which most likely reflects the metabolic requirements of the presynaptic functions of these spines. In several cases multiple spine heads were observed connected to the parent dendritic trunk via a common neck. In addition, dendritic varicosities making synaptic connections were noted. In the data set sampled, all of the reconstructions supported the hypothesis of divergence of granule cell connectivity: in no instance was a granule cell found to contact repeatedly the same mitral or tufted cell dendrite. Examination of the topological organization of reciprocal dendrodendritic synaptic connections with mitral/tufted cell dendrites revealed parallel rows of spine heads on mitral/tufted secondary dendrites separated by intervening zones of several microns in which no synaptic appositions were found. The results provide evidence regarding rules of connectivity underlying the function of local circuits in mediating lateral inhibition in the external plexiform layer of the olfactory bulb.
利用系列电子显微镜照片和三维计算机重建技术，研究了嗅球颗粒细胞棘突的形态及其与二尖瓣细胞和簇状细胞树突的树突 - 树突突触关系。大多数颗粒细胞棘突有蒂，头部呈大椭圆形，颈部（柄）比神经系统其他部位仅作为突触后棘突所描述的更长。这些棘突通常含有一个线粒体，这很可能反映了这些棘突突触前功能的代谢需求。在一些情况下，观察到多个棘突头部通过共同的颈部与母树突干相连。此外，还注意到有形成突触连接的树突膨体。在所采样的数据集中，所有重建结果都支持颗粒细胞连接发散的假说：未发现颗粒细胞反复接触同一个二尖瓣细胞或簇状细胞树突的情况。对与二尖瓣/簇状细胞树突相互的树突 - 树突突触连接的拓扑组织进行检查发现，二尖瓣/簇状细胞二级树突上的棘突头部平行排列，中间间隔数微米的区域未发现突触附着。这些结果为嗅球外丛状层介导侧向抑制的局部回路功能的连接规则提供了证据。
