Gracia-Llanes Francisco Javier, Crespo Carlos, Blasco-Ibáñez José Miguel, Marqués-Marí Ana Isabel, Martínez-Guijarro Francisco José
Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Valencia, E-46100, Burjasot, Spain.
Eur J Neurosci. 2003 Oct;18(7):1751-63. doi: 10.1046/j.1460-9568.2003.02895.x.
This study investigates the targets of the population of vasoactive intestinal polypeptide (VIP)-containing deep short-axon cells of the rat olfactory bulb (OB), combining single- and double-immunocytochemical approaches under light and electron microscopy. It has been assumed that deep short-axon cells innervate granule cells in the mammalian OB, but their synaptic connectivity has not been demonstrated to date. Our results indicate that, instead of the accepted scheme of the bulbar circuitry, VIP-containing deep short-axon cells are gamma-aminobutyric acid (GABA)ergic interneurons specialized in the selective innervation of other GABAergic deep short-axon cells. Their axons contact with the perisomatic region and the dendritic portions of subsets of deep short-axon cells that contain VIP, calbindin D-28k and neuropeptide Y. Electron microscopy reveals axo-somatic and axo-dendritic symmetrical synapses from VIP-containing boutons. Taken altogether, our data show that the VIP-containing deep short-axon cells of the rat OB form an interneuronal network that modulates the function of other interneurons different from granule cells. They might be involved indirectly in the inhibition or disinhibition of principal cells or might participate in the generation of oscillatory activity and in the synchronization of populations of interneurons and, then, of principal cells. Present data demonstrate that modulation of the OB by local circuits is more complex than the simple inhibition from periglomerular cells and granule cells, and remark the importance of considering the contribution of other classes of GABAergic interneurons different from periglomerular cells and granule cells to the bulbar circuitry.
本研究结合光镜和电镜下的单免疫细胞化学和双免疫细胞化学方法，对大鼠嗅球（OB）中含血管活性肠肽（VIP）的深层短轴突细胞群体的靶标进行了研究。人们一直认为，哺乳动物嗅球中的深层短轴突细胞支配颗粒细胞，但迄今为止，它们的突触连接尚未得到证实。我们的结果表明，与公认的嗅球回路模式不同，含VIP的深层短轴突细胞是γ-氨基丁酸（GABA）能中间神经元，专门选择性地支配其他GABA能深层短轴突细胞。它们的轴突与含VIP、钙结合蛋白D-28k和神经肽Y的深层短轴突细胞亚群的胞体周围区域和树突部分接触。电子显微镜显示含VIP的终扣形成轴体和轴树对称突触。综上所述，我们的数据表明，大鼠嗅球中含VIP的深层短轴突细胞形成了一个中间神经元网络，该网络调节不同于颗粒细胞的其他中间神经元的功能。它们可能间接参与对主细胞的抑制或去抑制，或者可能参与振荡活动的产生以及中间神经元群体进而主细胞群体的同步化。目前的数据表明，局部回路对嗅球的调节比来自球周细胞和颗粒细胞的简单抑制更为复杂，并强调了考虑不同于球周细胞和颗粒细胞的其他GABA能中间神经元类别对嗅球回路贡献的重要性。
