Changes in the Serotonin Immunoreactivities of Mucosal Mast Cells Following Vagus Nerve Stimulation in the Rat Gastrointestinal Tract

Jo, Byung Pil; Yang, Young Chul; Hwang, Tae Sun; Kang, Ho Suk

Abstract

Changes in the number, the immunoreactivities and the ultrastructures of sero- tonin immunoreactive mucosal mast cells[MMCs] in rat gastrointestinal tracts after vagus nerve stimulation were investigated by using light and electron microscopic immunocytochemical methods. The vagus nerves were electrically stimulated with a square wave pulse generator for a duration of 5 minutes each, a total of 8 times at 2 minute intervals. Serotonin immunoreactive cells of the connective tissues of the gastrointestinal tract were mainly located in the lamina propria, and a small number of the cells were also scattered in the submucosa. By using electron microscopic immunocytochemistry and Wright stain, the serotonin immunoreactive cells of the lamina propria and the submucosa were identified to be MMCs. A few large-sized serotonin immunoreactive connective tissue mast cells [CTMCs], showing strong metachromasia with the Wright stain, were located together with the MMCs in the submucosa of the stomach. In most of the gut regions of the control group, the majority of the MMCs did not show any serotonin immunoreactivities and only a few MMCs showed weak serotonin immunoreactivities. After stimulation of the vagus nerves, the number and the immnu- noreactivities of the serotonin immunoreactive MMCs dramatically increased in all gut regions observed, especially in the small intestines. In the samples treated with the electron microscopic immnunocytochemical methods, hardly any serotonin immunoreactivities were detected in the MMCs of the control group. However, the serotonin imrnunoreactivities of the MMCs were significantly increased after vagus nerve stimulation. The serotonin immnunoreactive products were localized, following vagal stimulation, both in the peripheral matrix of the granules and in the cytoplasm. Also, it was confirmed ultrastructurally that the Golgi complexes were expanded in the MMCs of the vagal stimulation group. The above results suggest that vagus nerve stimulation may activate serotonin biosynthesis in MMCs.