This research explored what chemical mediators are released by the intestinal mast cells under stress situation and whether they influence epithelial permeability in the mouse colon. Mast cells are a type of immune cell that release chemical granules that contain histamine, proteases, cytokines, etc. when stimulated by neuronal, hormonal, or paracrine signals. It has been demonstrated that mast cell deficient animals show no increased intestinal permeability after exposure to stress, suggesting that mast cells may play a crucial role in stress-induced disruption of the intestinal epithelial barrier. There is little research on the specific chemical mediators released by mast cells during stress and their roles in intestinal barrier function. Mice were divided into four groups (5/group): control male, control female, stress male, stress female. Stress animals were restrained for one hour/day for five consecutive days. Control animals were kept in their home cages and did not experience restraint. Following the final restraint/control session, the proximal colon was removed and dissected. The mucosa/submucosa of each preparation was mounted to an Ussing Chamber. Corticotropin-releasing factor (CRF) was added to the basolateral side of the chamber to stimulate mast cell degranulation and samples were taken before and 30-min after adding CRF. The levels of mast cell mediators (histamine, mast cell tryptase, tumor necrosis factor-alpha) were measured using enzyme-linked immunoassay (ELISA). The results for histamine release showed no significant difference in either the baseline histamine release or CRF-induced histamine release between control and stressed mice. Release of mast cell tryptase and tumor necrosis factor-alpha will be analyzed in the next few months. Our research has the potential to identify the key chemical mediators released by mast cells during stress. This could lead to further research to identify treatments that selectively target the mast mediators that increase intestinal permeability.