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

1.泌酸粘膜的神经支配：哺乳动物物种的胃粘膜受到几种类型的肽能神经纤维的严重神经支配：其中含胃泌素释放肽（GRP）的神经是最主要的。胆碱酯酶阳性神经在大鼠胃粘膜中分布密集，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核囊泡。大量无免疫反应性的透明小泡与大的核心小泡交织在一起，提示GRP与其他小分子量递质（可能是乙酰胆碱）共定位。应激诱导的GRP神经形态学变化：神经中GRP免疫反应性降低，通过本观察结果证实，含有GRP的大核心囊泡数量明显减少。同时，小透明囊泡数量减少，提示应激条件下GRP和乙酰胆碱共同释放. GRP神经与血管的关系：扫描电镜下显示GRP神经与毛细血管关系密切，与腺体细胞关系不密切。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调节血流方面也很重要，因为它们供应固有层中的粘膜毛细血管，并由血管神经元密集支配。胃粘膜中的肥大细胞：啮齿类动物中的肥大细胞含有5-羟色胺和组胺。但胃粘膜中的肥大细胞不具有5-羟色胺合成酶，而腹膜中的肥大细胞则具有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.