Gulyás A I, Hájos N, Freund T F
Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.
J Neurosci. 1996 May 15;16(10):3397-411. doi: 10.1523/JNEUROSCI.16-10-03397.1996.
Spine-free calretinin-immunoreactive (CR-IR) interneurons form a subpopulation of GABAergic cells in the rat hippocampus. A characteristic feature of these cells--located in all areas and layers--is the frequent dendro-dendritic and axo-dendritic contacts they form with each other. In this study we examined in detail the connectivity of these neurons by reconstructing their dendritic and axonal arbor and by identifying their postsynaptic targets. Radially running dendrites of CR-IR cells, located in different layers, intermingled into long braids. An average cell was in contact with dendrites of three to seven other CR-IR cells. Reconstruction of the dendritic trees from six consecutive sections demonstrated that at least 15 cells may participate in a dendro-dendritically connected cluster. Electron microscopical examination revealed that regularly spaced zonula adherentia connect the touching dendrites. The postsynaptic targets of CR-IR neurons have been examined using postembedding immunogold staining for GABA. CR-containing GABA-immunoreactive axons of local origin formed multiple symmetrical synaptic contacts (two to five) exclusively on GABAergic dendrites (CR-negative as well as CR-positive). Two to 10 CR-IR axons may converge onto a single CR-IR neuron, often from cells belonging to the same dendro-dendritically connected cluster. Using double immunocytochemistry, CR-IR cells were shown to heavily innervate calbindin D28k-containing interneurons and VIP-containing basket cells but avoided the parvalbumin-containing basket and axo-axonic cells. The unique connectivity of CR-IR cells may enable them to play a crucial role in the generation of synchronous, rhythmic hippocampal activity by controlling other interneurons terminating on different dendritic and somatic compartments of principal cells.
无棘钙视网膜蛋白免疫反应性（CR-IR）中间神经元构成大鼠海马中GABA能细胞的一个亚群。这些细胞的一个特征——位于所有区域和层——是它们彼此之间频繁形成树突-树突和轴突-树突接触。在本研究中，我们通过重建这些神经元的树突和轴突分支并识别其突触后靶点，详细研究了它们的连接性。位于不同层的CR-IR细胞的径向树突相互交织成辫状。一个平均的细胞与三到七个其他CR-IR细胞的树突接触。对连续六个切片中的树突进行重建表明，至少15个细胞可能参与一个树突-树突连接的簇。电子显微镜检查显示，规则间隔的紧密连接连接着相互接触的树突。使用包埋后免疫金染色法检测GABA，研究了CR-IR神经元的突触后靶点。来自局部的含CR的GABA免疫反应性轴突仅在GABA能树突（CR阴性和CR阳性）上形成多个对称突触接触（两到五个）。两到10个CR-IR轴突可能汇聚到单个CR-IR神经元上，通常来自属于同一个树突-树突连接簇的细胞。使用双重免疫细胞化学方法显示，CR-IR细胞大量支配含钙结合蛋白D28k的中间神经元和含血管活性肠肽的篮状细胞，但避开含小白蛋白的篮状细胞和轴突-轴突细胞。CR-IR细胞独特的连接性可能使它们通过控制终止于主细胞不同树突和胞体区室的其他中间神经元，在同步、节律性海马活动的产生中发挥关键作用。
