Genetic approach to trace construction of taste neuronal circuitries

为了深入了解味觉信息是如何通过大脑中特定的核中继来处理和整合的，并解决味觉神经元回路构建的潜在机制，我们应用遗传学方法通过选择性表达跨突触示踪剂tWGA-DsRed来描绘苦味和甜味的神经元回路，在小鼠的苦味或甜味反应味觉受体细胞中。在全脑的连续冠状切片中检测了从味觉反应细胞或甜味反应细胞转移的tWGA-DsRed的空间分布。在全脑的三维图像中分析tWGA-DsRed标记的神经元的位置，所述三维图像通过组装从连续切片图像提取的脑结构来重建。虽然标记密度可能受到示踪剂的运输和降解效率的影响，这可能在神经元类型之间变化，但标记的神经元 ...更多信息 通过tWGA-DsRed，从甜味反应性味觉受体细胞转移的位于孤束核和味觉皮层的更前部区域，与来自甜味反应性味觉受体细胞的相比。在成年小鼠的味觉皮层中，两种品系的tWGA-DsRed标记神经元的分散区域似乎沿着前后轴部分重叠。这种遗传学方法可能是有价值的，调查的细胞和分子方面的建设和完善的味觉神经元回路介导的味觉歧视。在甜味神经元回路的发育阶段，位于孤束核和味觉皮层的最前部的神经元最初接受来自甜味反应味觉受体细胞的tWGA-DsRed，显示出甜和苦输入之间的明显分离。结果表明，预先指定的神经元对可以选择性地构建神经元回路来处理苦味或甜味信息。少

To gain insight into how gustatory information is processed and integrated by the specific nuclear relays in the brain, and to address the mechanisms underlying the construction of taste neuronal circuitries, we applied a genetic approach to delineate the neuronal circuitries of bitter and sweet taste by selectively expressing the transsynaptic tracer, tWGA-DsRed, in either bitter-or sweet-responsive taste receptor cells in mice. The spatial distribution of tWGA-DsRed that was transferred from either bitter-or sweet-responsive taste receptor cells was detected in the serial coronal sections of the whole brain. Locations of tWGA-DsRed-labeled neurons were analyzed in three-dimensional images of the whole brain, which were reconstructed by assembling the brain structures extracted from the serial section images. Although the labeling density is likely to be influenced by the efficiencies of transport and degradation of the tracer, which may vary among neuronal types, the neurons labeled … More by tWGA-DsRed that was transferred from sweet-responsive taste receptor cells were located in the more anterior regions of both the solitary tract nuclei and the gustatory cortex, compared with those from bitter-responsive taste receptor cells. In the gustatory cortex of adult mice, the dispersed areas of tWGA-DsRed-labeled neurons in two strains appeared to partly overlap along the anterior-posterior axis. This genetic approach may be valuable for investigating the cellular and molecular aspects underlying the construction and refinement of taste neuronal circuitries to mediate taste discrimination. During the developmental stages of sweet taste neuronal circuitries, the neurons located in the most anterior parts of both the solitary tract nuclei and the gustatory cortex initially received tWGA-DsRed originating from sweet-responsive taste receptor cells, showing clear segregation between sweet and bitter inputs. The results suggest that the pre-specified neuron pairs may selectively construct the neuronal circuitries to process either bitter or sweet taste information. Less