Chiocchetti Roberto, Grandis Annamaria, Bombardi Cristiano, Lucchi Maria L, Dal Lago Davide Tadini, Bortolami Ruggero, Furness John B
Department of Veterinary Morphophysiology and Animal Productions, University of Bologna, 40064 Bologna, Ozzano Emilia, Italy.
Cell Tissue Res. 2006 Feb;323(2):183-96. doi: 10.1007/s00441-005-0075-2. Epub 2005 Oct 14.
To investigate extrinsic origins of calcitonin gene-related peptide immunoreactive (CGRP-IR) nerve fibres in the sheep ileum, the retrograde fluorescent tracer Fast Blue (FB) was injected into the ileum wall. Sections of thoraco-lumbar dorsal root ganglia (DRG) and distal (nodose) vagal ganglia showing FB-labelled neurons were processed for CGRP immunohistochemistry. The distribution of CGRP-IR in fibres and nerve cell bodies in the ileum was also studied. CGRP-IR enteric neurons were morphometrically analysed in myenteric (MP) and submucosal plexuses (SMP) of lambs (2-4 months). Sensory neurons retrogradely labelled with FB were scattered in T5-L4 DRG but most were located at the upper lumbar levels (L1-L3); only a minor component of the extrinsic afferent innervation of the ileum was derived from nodose ganglia. In the DRG, 57% of retrogradely labelled neurons were also CGRP-IR. In cryostat sections, a dense network of CGRP-IR fibres was observed in the lamina propria beneath the epithelium, around the lacteals and lymphatic follicles (Peyer's platches), and along and around enteric blood vessels. Rare CGRP-IR fibres were also present in both muscle layers. Dense pericellular baskets of CGRP-IR fibres were observed around CGRP-negative somata. The only CGRP-IR nerve cells were well-defined Dogiel type II neurons localised in the MP and in the external and internal components of the SMP. CGRP-IR neurons in the myenteric ganglia were significantly larger than those in the submucosal ganglia (mean profile areas: about 1,400 mum(2) for myenteric neurons, 750 mum(2) for submucosal neurons). About 6% of myenteric neurons and 25% of submucosal neurons were CGRP-IR Dogiel type II neurons. The percentages of CGRP-IR neurons that were also tachykinin-IR were about 9% (MP) and 42% (SMP), whereas no CGRP-IR neurons exhibited immunoreactivity for vasoactive intestinal peptide, nitric oxide synthase or tyrosine hydroxylase in either plexus. Thus, CGRP immunoreactivity occurs in the enteric nervous system of the sheep ileum (as in human small intestine and MP of pig ileum) in only one morphologically defined type of neuron, Dogiel type II cells. These are probably intrinsic primary afferent neurons.
为研究绵羊回肠中降钙素基因相关肽免疫反应性（CGRP-IR）神经纤维的外源性起源，将逆行荧光示踪剂快蓝（FB）注入回肠壁。对显示FB标记神经元的胸腰段背根神经节（DRG）和远端（结状）迷走神经节切片进行CGRP免疫组织化学处理。还研究了回肠中CGRP-IR在纤维和神经细胞体中的分布。对羔羊（2 - 4个月）肌间神经丛（MP）和黏膜下神经丛（SMP）中的CGRP-IR肠神经元进行形态计量分析。经FB逆行标记的感觉神经元散在于T5 - L4 DRG中，但大多数位于腰段上部（L1 - L3）；回肠的外源性传入神经支配中只有一小部分来自结状神经节。在DRG中，57%的逆行标记神经元也是CGRP-IR。在冰冻切片中，在上皮下方的固有层、乳糜管和淋巴滤泡（派伊尔结）周围以及肠血管周围和沿肠血管观察到密集的CGRP-IR纤维网络。在两层肌肉中也存在少量CGRP-IR纤维。在CGRP阴性的胞体周围观察到密集的CGRP-IR纤维细胞周篮。唯一的CGRP-IR神经细胞是明确的多极II型神经元，位于MP以及SMP的外部和内部成分中。肌间神经节中的CGRP-IR神经元明显大于黏膜下神经节中的（平均轮廓面积：肌间神经元约1400μm²，黏膜下神经元750μm²）。约6%的肌间神经元和25%的黏膜下神经元是CGRP-IR多极II型神经元。同时也是速激肽-IR的CGRP-IR神经元百分比约为9%（MP）和42%（SMP），而在任一神经丛中，没有CGRP-IR神经元对血管活性肠肽、一氧化氮合酶或酪氨酸羟化酶表现出免疫反应性。因此，CGRP免疫反应性仅在一种形态学上明确的神经元类型，即多极II型细胞中出现在绵羊回肠的肠神经系统中（如同在人类小肠和猪回肠的MP中一样）。这些可能是内在的初级传入神经元。
