Marfurt C F, Del Toro D R
J Comp Neurol. 1987 Jul 15;261(3):450-9. doi: 10.1002/cne.902610309.
The methods of transganglionic transport of horseradish peroxidase (HRP) and horseradish peroxidase--wheat germ agglutinin (HRP-WGA) were used to determine the location within the trigeminal ganglion of the primary afferent neurons that innervate the rat central cornea, and the brainstem and spinal cord termination sites of these cells. In each of 18 animals, solutions of HRP or HRP-WGA were applied to the scarified corneal surface and allowed to infiltrate into the corneal epithelium and stroma for 15 minutes. Postmortem examination of the corneal whole mounts from the experimental animals, and of corneas and neural tissues from several control animals, showed that the HRP/HRP-WGA remained confined to the central cornea with no spread into adjacent intra- or extraorbital tissues. HRP-labeled corneal afferent somata were located in the dorsal part of the ophthalmic region of the ipsilateral trigeminal ganglion. The central fibers of the corneal afferent neurons projected very heavily to interstitial nuclei of Cajal in the spinal tract of V at the level of caudal pars interpolaris and rostral pars caudalis, lightly to the pars caudalis/C1 transition zone, and sparsely to the dorsal horn of spinal cord segments C1-C3. The trigeminal main sensory nucleus, pars oralis, the rostral three-fourths of pars interpolaris, and an extensive midregion of pars caudalis were totally devoid of reaction product. Terminal fields in caudal pars caudalis and in the spinal cord dorsal horn were concentrated largely in the outer half of lamina II, with lesser accumulations in lamina I, the deeper half of lamina II, and in lamina III. The present study demonstrates for the first time by means of an anatomical tracing procedure the brainstem termination sites of corneal afferent neurons in the rat. The patchy, discontinuous nature of the corneal afferent projection to the caudal trigeminal brainstem nuclear complex (TBNC), and the total lack of corneal projections to rostral subdivisions of the TBNC, provide an exception to the general rule of trigeminal organization in which most areas of the head and face are represented as continuous columns throughout the rostrocaudal extent of the ipsilateral TBNC.
采用辣根过氧化物酶（HRP）和辣根过氧化物酶-小麦胚芽凝集素（HRP-WGA）的跨神经节运输方法，来确定支配大鼠角膜中央的初级传入神经元在三叉神经节内的位置，以及这些细胞在脑干和脊髓的终末部位。在18只动物中，将HRP或HRP-WGA溶液应用于划痕的角膜表面，使其渗入角膜上皮和基质15分钟。对实验动物的角膜全层标本以及几只对照动物的角膜和神经组织进行死后检查，结果显示HRP/HRP-WGA仍局限于角膜中央，未扩散至相邻的眶内或眶外组织。HRP标记的角膜传入神经元胞体位于同侧三叉神经节眼支区域的背侧部分。角膜传入神经元的中枢纤维大量投射至三叉神经脊束核尾侧极间部和头侧尾部水平的Cajal间质核，少量投射至尾部/C1过渡区，稀疏投射至脊髓C1-C3节段的背角。三叉神经主感觉核口部、极间部头侧四分之三以及尾部广泛的中部区域完全没有反应产物。尾侧尾部和脊髓背角的终末场主要集中在Ⅱ层外侧半，在Ⅰ层、Ⅱ层内侧半和Ⅲ层有较少的聚集。本研究首次通过解剖追踪方法证实了大鼠角膜传入神经元在脑干的终末部位。角膜传入纤维向尾侧三叉神经脑干核复合体（TBNC）投射的斑片状、不连续性质，以及TBNC头侧亚区完全缺乏角膜投射，为三叉神经组织的一般规则提供了一个例外，在该规则中，头面部的大多数区域在同侧TBNC的整个 rostrocaudal 范围内表现为连续的柱状结构。
