Immunohistochemical and ultrastructural study of GRP-containing nerves in the gastric mucosa

1.含氧粘膜的神经支配：哺乳动物的胃粘膜由几种类型的肽能神经纤维支配，其中以胃泌素释放肽(GRP)神经为主。结果：1.大鼠胃粘膜内胆碱酯酶阳性神经密集分布，与GRP神经一致，肾上腺素能神经较少。含GRP神经的超微结构：GRP免疫反应选择性地定位于神经纤维肿胀部分聚集的大的核心小泡中。大量无免疫反应的小透明小泡与大的核心小泡共存，提示GRP与其他小分子递质(可能是乙酰胆碱)共存。应激诱导的GRP神经形态改变：超微结构观察证实神经内GRP免疫反应性降低，含GRP的大小泡数量明显减少。同时，透明小泡数量减少，提示应激条件下GRP和乙酰胆碱共同释放。GRP神经与血管的解剖关系：扫描电子显微镜下可见GRP神经与毛细血管关系密切，但与腺体细胞关系不大。毛细血管伴随着周细胞，周细胞本质上是收缩的，因此能够收缩，最终导致粘膜缺血和损伤。粘膜肌层周围的小动脉可能在血流调节中也很重要，因为它们支持固有层的粘膜毛细血管，并被血管运动神经元密集支配。胃粘膜中的肥大细胞：啮齿动物的肥大细胞含有5-羟色胺和组胺。然而，与腹膜肥大细胞不同，胃粘膜中的肥大细胞不具有5-羟色胺合成酶。

1. Innervation of the oxyntic mucosa : The gastric mucosa of mammalian species is heavily innervated by several types of peptidergic nerve fibers : gastrin-releasing peptide (GRP)-containing nerves being most predominant among them. Cholinesterase-positive nerves were densely distributed in the rat gastric mucosa and identical to the GRP nerves, while adrenergic nerves were few.2. Ultrastructure of GRP-containing nerves : The immunoreactivity for GRP was selectively localized in large cored vesicles gathering in the swollen parts of nerve fibers. Numerous small clear vesicles free of the immunoreactivity were interm : Engled with the large cored vesicles, suggesting the colocalization of GRP and other transmitter with a small molecular weight, possibly acetylcholine.3. Stress-induced morphological change of GRP nerves : The decreased GRP immunoreactivity in the nerves was ultrastructurally confirmed by the present observation showing marked decrease in number of the GRP-containing large cored vesicles. Simultaneously, small clear vesicles decreased in number, suggesting the corelease of GRP and acetylcholine under stress condition.4. Topographic relation of GRP nerves and blood vessels : The GRP nerves were shown under SEM to be closely related with capillaries, but not with any glandular cells. The capillaries were accompanied by pericytes which are contractile in nature, thus being able to contract, finally causing mucosal ischemia and damage. Arterioles around the lamina muscularis mucosas might be also important in regulation of blood flow, since they suppiyed the mucosal capillaries in the lamina propria and were densely innervated by vasomotor neurons.5. Mast cells in the gastric mucosa : Mast cells in rodents contain serotonin as well as histamine. However, they in the gastric mucosa did not possess a synthesizing enzyme for serotonin, in contrast to peritoneal mast cells.