Anderson C W, Nishikawa K C
Department of Biological Sciences, Northern Arizona University, Flagstaff 86011-5640, USA.
Brain Res. 1997 Oct 17;771(2):285-91. doi: 10.1016/s0006-8993(97)00803-2.
Previously, we suggested that afferents are present in the hypoglossal nerve of the leopard frog, Rana pipiens. The basis for this was behavioral data obtained after transection of the hypoglossal nerve. These afferents coordinate the timing of tongue protraction with mouth opening during feeding. The goal of the present study was to define anatomically these hypoglossal afferents in Rana pipiens. Retrograde tracing was performed using horseradish peroxidase, fluorescent dextran amines and neurobiotin. Data show that the cell bodies of hypoglossal afferents are located in the dorsal root ganglion of the third spinal nerve and enter the brainstem through its dorsal root. The afferents ascend in the dorsomedial funiculus and move laterally after they pass the obex. They project in the granular layer of the cerebellum and the medial reticular formation. The cervical afferents that travel in this pathway are known to carry proprioceptive and cutaneous sensory information. We hypothesize that the presence of afferents in the hypoglossal nerve is a derived characteristic of anurans, which has resulted from the re-routing of afferent fibers from the third spinal nerve into the hypoglossal nerve. The appearance of hypoglossal afferents coincides with the morphological acquisition of a highly protrusible tongue.
此前，我们曾提出豹蛙（北美牛蛙）的舌下神经中存在传入神经。这一结论的依据是舌下神经横断后获得的行为学数据。这些传入神经在进食过程中协调伸舌与张口的时间。本研究的目的是从解剖学上确定北美牛蛙的这些舌下神经传入神经。使用辣根过氧化物酶、荧光葡聚糖胺和神经生物素进行逆行追踪。数据显示，舌下神经传入神经的细胞体位于第三脊髓神经的背根神经节，通过其背根进入脑干。传入神经在背内侧索中上行，经过闩部后向外侧移动。它们投射到小脑颗粒层和内侧网状结构。已知沿此路径走行的颈传入神经携带本体感觉和皮肤感觉信息。我们推测，舌下神经中传入神经的存在是无尾类动物的一个衍生特征，这是由于传入纤维从第三脊髓神经重新路由到舌下神经所致。舌下神经传入神经的出现与高度可伸展舌头的形态学获得相一致。
