Domoto T, Yang H, Bishop A E, Polak J M, Oki M
Department of Anatomy, Shimane Medical University, Izumo, Japan.
Neurosci Res. 1992 Oct;15(1-2):64-73. doi: 10.1016/0168-0102(92)90018-8.
The distributions of nerve fibers containing calcitonin gene-related peptide (CGRP), substance P (SP) and galanin (GAL) were examined in the rat rectum of mutants rats, aganglionic rats (AGRs), which completely lack the intramural nerve cells in the large intestine, and of their normal littermates. The origin of extrinsic peptide-containing nerve fibers was examined using retrograde tracing combined with immunohistochemistry in normal rats. In the rectum of normal rats, CGRP-, SP- and GAL-immunoreactive varicose fibers were observed throughout all layers of the rectal wall, and immunoreactive nerve cells were present in the enteric ganglia of colchicine-treated rats. In the aganglionic rectum of AGR, a rich supply of CGRP-immunoreactive fibers was observed in the mucosa, around the blood vessels, and in the submucous and intermuscular spaces. SP- and GAL-immunoreactive fibers in the aganglionic rectum showed a similar distribution to CGRP-immunoreactive fibers but were less dense. These results suggest that most of CGRP-positive fibers in the rectum are extrinsic whereas a large part of SP- or GAL-positive fibers are intrinsic. Fluoro-gold injected into the upper rectum of normal rat labelled nerve cells (less than 10% of total ganglion cells) in the lumbar (L1 and L2) and lumbosacral (L6 and S1) dorsal root ganglia. More than half of nerve cells in the dorsal root ganglia (L6 and S1) projecting to the rectum were immunoreactive for CGRP, and less than 10% were immunoreactive for SP or GAL. Comparison of serial sections of the dorsal root ganglion revealed that about half of the CGRP-immunoreactive cells were also positive for SP or GAL. These results indicate that SP- or GAL-positive neurons projecting to the rectum are scarce in the dorsal root ganglia. The present investigation suggests that CGRP-containing nerves are visceral afferents forming a major component of the sensory innervation of the rat rectum, and SP- and GAL-containing nerves which share their extrinsic origins appear to form a lesser proportion of the sensory innervation.
在完全缺乏大肠壁内神经细胞的突变大鼠即无神经节大鼠（AGR）及其正常同窝仔鼠的大鼠直肠中，研究了含降钙素基因相关肽（CGRP）、P物质（SP）和甘丙肽（GAL）的神经纤维分布。在正常大鼠中，采用逆行追踪结合免疫组织化学方法研究了含肽类的外在神经纤维的起源。在正常大鼠的直肠中，在直肠壁的所有层均观察到CGRP、SP和GAL免疫反应性曲张纤维，在秋水仙碱处理大鼠的肠神经节中存在免疫反应性神经细胞。在AGR的无神经节直肠中，在黏膜、血管周围以及黏膜下层和肌层间隙观察到丰富的CGRP免疫反应性纤维。无神经节直肠中的SP和GAL免疫反应性纤维显示出与CGRP免疫反应性纤维相似的分布，但密度较低。这些结果表明，直肠中大多数CGRP阳性纤维是外在性的，而大部分SP或GAL阳性纤维是内在性的。向正常大鼠的上直肠注射荧光金标记了腰段（L1和L2）和腰骶段（L6和S1）背根神经节中的神经细胞（占神经节细胞总数的不到10%）。投射到直肠的背根神经节（L6和S1）中超过一半的神经细胞对CGRP呈免疫反应性，对SP或GAL呈免疫反应性的不到10%。背根神经节连续切片的比较显示，约一半的CGRP免疫反应性细胞对SP或GAL也呈阳性。这些结果表明，投射到直肠的SP或GAL阳性神经元在背根神经节中很少见。本研究表明，含CGRP的神经是内脏传入神经，构成大鼠直肠感觉神经支配的主要成分，而具有共同外在起源的含SP和GAL的神经似乎在感觉神经支配中所占比例较小。
