Zaidi Faisal N, Todd Krista, Enquist Lynn, Whitehead Mark C
Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093, USA.
J Comp Neurol. 2008 Dec 20;511(6):753-72. doi: 10.1002/cne.21869.
The present study evaluates the central circuits that are synaptically engaged by very small subsets of the total population of geniculate ganglion cells to test the hypothesis that taste ganglion cells are heterogeneous in terms of their central connections. We used transsynaptic anterograde pseudorabies virus labeling of fungiform taste papillae to infect single or small numbers of geniculate ganglion cells, together with the central neurons with which they connect, to define differential patterns of synaptically linked neurons in the taste pathway. Labeled brain cells were localized within known gustatory regions, including the rostral central subdivision (RC) of the nucleus of the solitary tract (NST), the principal site where geniculate axons synapse, and the site containing most of the cells that project to the parabrachial nucleus (PBN) of the pons. Cells were also located in the rostral lateral NST subdivision (RL), a site of trigeminal and sparse geniculate input, and the ventral NST (V) and medullary reticular formation (RF), a caudal brainstem pathway leading to reflexive oromotor functions. Comparisons among cases, each with a random, very small subset of labeled geniculate neurons, revealed "types" of central neural circuits consistent with a differential engagement of either the ascending or the local, intramedullary pathway by different classes of ganglion cells. We conclude that taste ganglion cells are heterogeneous in terms of their central connectivity, some engaging, predominantly, the ascending "lemniscal," taste pathway, a circuit associated with higher order discriminative and homeostatic functions, others engaging the "local," intramedullary "reflex" circuit that mediates ingestion and rejection oromotor behaviors.
本研究评估了由膝状神经节细胞总数中非常小的子集通过突触连接的中枢回路，以检验味觉神经节细胞在其中枢连接方面存在异质性这一假设。我们使用经突触的逆行伪狂犬病病毒标记菌状味蕾乳头，来感染单个或少量的膝状神经节细胞以及它们与之连接的中枢神经元，以确定味觉通路中突触连接神经元的差异模式。标记的脑细胞定位于已知的味觉区域内，包括孤束核（NST）的嘴侧中央亚区（RC），这是膝状轴突突触形成的主要部位，以及包含大部分投射到脑桥臂旁核（PBN）的细胞的部位。细胞也位于嘴侧外侧NST亚区（RL），这是三叉神经和稀疏膝状神经输入的部位，以及腹侧NST（V）和延髓网状结构（RF），这是一条通向反射性口部运动功能的脑干尾侧通路。对每个病例进行比较，每个病例都有随机的、非常小的一部分标记的膝状神经元子集，结果揭示了中枢神经回路的“类型”，这与不同类别的神经节细胞对上行或局部髓内通路的差异参与一致。我们得出结论，味觉神经节细胞在其中枢连接性方面是异质的，一些细胞主要参与上行的“lemniscal”味觉通路，这是一个与高阶辨别和稳态功能相关的回路，另一些细胞则参与“局部”的髓内“反射”回路，该回路介导摄取和排斥口部运动行为。
