Cox R G, Peusner K D
George Washington University School of Medicine, Washington, D.C. 20037.
J Comp Neurol. 1990 Jul 22;297(4):564-81. doi: 10.1002/cne.902970409.
The purpose of the present study was to place horseradish peroxidase on the distal processes of the three ampullary nerves in 6-8-week-old chickens so that we could identify the ganglion cells associated with each nerve and trace the specific central pathways taken by each nerve in the brainstem. We are especially interested in the pathways of the colossal vestibular fibers, which may play a role in a fast reflex pathway as suggested by their large caliber and electrotonic mode of transmission in the tangential vestibular nucleus. The cells of origin of each ampullary nerve occupy discrete portions of the vestibular ganglion. Those vestibular ganglion cells giving rise to the posterior ampullary nerve (PAN) occupy the posterior portion of Scarpa's ganglion; the ganglion cells producing the anterior (AAN) and lateral (LAN) ampullary nerves occupy the anterior ganglion, within the dorsal and ventral portions, respectively. Centrally the vestibular fibers occupy discrete portions of the tangential vestibular nucleus before bifurcating into ascending and descending tracts. The tangential nucleus receives afferents from the colossal fibers, which form spoon endings, and also from the fine vestibular fibers, which form small terminals. The ascending fibers of the posterior ampullary nerve are associated with the nucleus piriformis; the ascending fibers of the anterior and lateral ampullary nerves occupy discrete cell groups of the vestibulo-cerebellar nucleus. All three ampullary nerves have descending branches that course through the retrotangential nucleus into the descending vestibular nucleus (DVN). Within the descending vestibular nucleus, the descending fibers of the posterior ampullary nerve run dorsally and centrally, whereas fibers of the anterior ampullary nerve course ventromedially, and the lateral ampullary nerve fibers take a ventrolateral course until all three fiber bundles converge in the posterior tip of the descending vestibular nucleus. The ascending and descending fibers of each ampullary nerve form collaterals that pass to the ventrolateral and dorsomedial parts of the medial vestibular nucleus. These collaterals are derived exclusively from the fine and medium diameter vestibular fibers. Some of these ascending fibers form a distinctive tract that courses posteriorly within medial regions of the dorsomedial part of the medial vestibular nucleus. The colossal vestibular fibers, which are found within all three ampullary nerves, conform to the ampullary pathways as described, excluding the innervation of the medial vestibular nucleus.
本研究的目的是将辣根过氧化物酶置于6至8周龄鸡的三条壶腹神经的远端突起上，以便我们能够识别与每条神经相关的神经节细胞，并追踪每条神经在脑干中所走的特定中枢通路。我们尤其对巨大前庭纤维的通路感兴趣，正如它们在切向前庭核中的大口径和电紧张传播模式所表明的那样，这些纤维可能在快速反射通路中发挥作用。每条壶腹神经的起源细胞占据前庭神经节的不同部分。那些发出后壶腹神经（PAN）的前庭神经节细胞占据斯卡帕神经节的后部；产生前壶腹神经（AAN）和外侧壶腹神经（LAN）的神经节细胞分别占据前神经节的背侧和腹侧部分。在前庭纤维进入切向前庭核的离散部分后，再分成升支和降支。切向核接收来自形成匙状终末的巨大纤维以及形成小终末的细前庭纤维的传入纤维。后壶腹神经的升支与梨状核相关；前壶腹神经和外侧壶腹神经的升支占据前庭小脑核的离散细胞群。所有三条壶腹神经都有降支，它们穿过切向后核进入降前庭核（DVN）。在降前庭核内，后壶腹神经的降支向背侧和中央走行，而前壶腹神经的纤维向腹内侧走行，外侧壶腹神经纤维走行于腹外侧，直到所有三个纤维束在前庭核后部尖端汇聚。每条壶腹神经的升支和降支形成侧支，这些侧支通向内侧前庭核的腹外侧和背内侧部分。这些侧支仅来自细和中等直径的前庭纤维。其中一些升支形成一条独特的束，在背内侧部分的内侧前庭核的内侧区域向后走行。在所有三条壶腹神经中都能找到的巨大前庭纤维，遵循上述壶腹通路，但不包括内侧前庭核的神经支配。
