Papp E C, Hajos N, Acsády L, Freund T F
Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest.
Neuroscience. 1999 May;90(2):369-82. doi: 10.1016/s0306-4522(98)00455-2.
Vasoactive intestinal polypeptide-immunoreactive interneurons are known to form three anatomically and neurochemically well-characterized neuron populations in the hippocampus. Two of these establish synaptic contacts selectively with other GABAergic cells (interneuron-selective cells), whereas the third type innervates pyramidal cell bodies and proximal dendrites like a conventional basket cell. Our aim was to examine which of the vasoactive intestinal polypeptide-containing interneuron populations are among the targets of GABAergic septohippocampal and serotonergic raphe-hippocampal pathways. Anterograde tracing with Phaseolus vulgaris leucoagglutinin combined with double immunocytochemistry for vasoactive intestinal polypeptide was used at the light and electron microscopic levels. Our results show that both interneuron-selective cells and vasoactive intestinal polypeptide-containing basket cells receive synaptic input from the medial septum and median raphe nucleus. The GABAergic component of the septohippocampal pathway establishes multiple contacts on both cell types. In the case of the raphe-hippocampal projection, single or double contacts were more frequent on vasoactive intestinal polypeptide-positive interneuron selective cells (76%), whereas multiple contacts predominated on basket cells (83%). The extrinsic GABAergic innervation of interneuron-selective cells in the hippocampus indicates a complex interaction among GABAergic systems, which might ensure the timing and rhythmic synchronization of inhibitory processes in the hippocampus. On the other hand, our results suggest that the serotonergic effect on perisomatic inhibition is exerted via vasoactive intestinal polypeptide-containing basket cells that are functionally distinct from their parvalbumin-positive relatives, which appear to escape control of serotonergic as well as local interneuron-selective cells.
已知血管活性肠肽免疫反应性中间神经元在海马体中形成三个在解剖学和神经化学上特征明确的神经元群体。其中两个群体选择性地与其他γ-氨基丁酸能细胞（中间神经元选择性细胞）建立突触联系，而第三种类型则像传统的篮状细胞一样支配锥体细胞体和近端树突。我们的目的是研究哪些含血管活性肠肽的中间神经元群体是γ-氨基丁酸能隔海马通路和5-羟色胺能中缝海马通路的靶点。在光学和电子显微镜水平上，使用菜豆白细胞凝集素进行顺行追踪并结合血管活性肠肽的双重免疫细胞化学。我们的结果表明，中间神经元选择性细胞和含血管活性肠肽的篮状细胞都接受来自内侧隔区和中缝正中核的突触输入。隔海马通路的γ-氨基丁酸能成分在这两种细胞类型上都建立了多个突触联系。就中缝海马投射而言，在血管活性肠肽阳性的中间神经元选择性细胞上，单个或双重突触联系更为常见（76%），而在篮状细胞上，多个突触联系占主导（83%）。海马体中中间神经元选择性细胞的外在γ-氨基丁酸能神经支配表明γ-氨基丁酸能系统之间存在复杂的相互作用，这可能确保海马体中抑制过程的时间和节律同步。另一方面，我们的结果表明，5-羟色胺对躯体周围抑制的作用是通过含血管活性肠肽的篮状细胞发挥的，这些细胞在功能上与其小白蛋白阳性的亲属不同，后者似乎不受5-羟色胺能以及局部中间神经元选择性细胞的控制。
