AIM: To investigate the effects of psychological stress on small intestinal motility and bacteria and mucosa in mice, and to explore the relationship between small intestinal dysfunction and small intestinal motility and bacteria and mucosa under psychological stress. METHODS: Sixty mice were randomly divided into psychological stress group and control group. Each group were subdivided into small intestinal motility group (n= 10), bacteria group (n = 10), and D-xylose administered to stomach group (n= 10). An animal model with psychological stress was established housing the mice with a hungry cat in separate layers of a two-layer cage. A semi-solid colored marker (carbon-ink) was used for monitoring small intestinal transit. The proximal small intestine was harvested under sterile condition and processed for quantitation for aerobes (Escherichia coli) and anaerobes (Lactobacilli). The quantitation of bacteria was expressed as Iog10(colony forming units/g). D-xylose levels in plasma were measured for estimating trie damage of small intestinal mucosa. RESULTS: Small intestinal transit was inhibited (39.80±9.50% vs 58.79±11.47%,P<0.01) in mice after psychological stress, compared with the controls. Psychological stress resulted in quantitative alterations in the aerobes (E.coli). There was an increase in the number of E coli in the proximal small intestinal flora (1.78±0.30 log10(CFU/g) vs 1.37±0.21 log10(CFU/g), P<0.01), and there was decrease in relative proportion of Lactobacilli and E.coli of stressed mice (0.53±0.63 vs 1.14±1.07,P<0.05), while there was no significant difference in the anaerobes (Lactobacilli) between the two groups (2.31±0.70 log10 (CFU/g) vs 2.44±0.37 log10(CFU/g), P>0.05). D-xylose concentrations in plasma in psychological stress mice were significantly higher than those in the control group (2.90±0.89 mmol/L vs 0.97±0.33 mmol/L, P<0.01). CONCLUSION: Small intestinal dysfunction under psychological stress may be related to the small intestinal motility disorder and dysbacteriosis and the damage of mucosa probably caused by psychological stress. To investigate the effects of psychological stress on small intestinal motility and bacteria and mucosa in mice, and to explore the relationship between small intestinal dysfunction and small intestinal motility and bacteria and mucosa under psychological stress. METHODS: Sixty mice were randomly divided into psychological stress group and control group. Each group was subdivided into small intestinal motility group (n = 10), bacteria group (n = 10), and D-xylose administered to stomach group established housing the mice with a hungry cat in separate layers of a two-layer cage. A semi-solid colored marker (carbon-ink) was used for monitoring small intestinal transit. The proximal small intestine was harvested under sterile condition and processed for quantitation for aerobes (Escherichia coli) and anaerobes (Lactobacilli). The quantitation of bacteria was expressed as Iog10 (colony forming units / g). D-xylose levels in plasma we RESULTS: Small intestinal transit was inhibited (39.80 ± 9.50% vs 58.79 ± 11.47%, P <0.01) in mice after psychological stress, compared with the controls. Psychological stress resulted in quantitative alterations in the aerobes (E. coli). There was an increase in the number of E coli in the proximal small intestinal flora (1.78 ± 0.30 log10 (CFU / g) vs 1.37 ± 0.21 log10 (CFU / g) , and there was decrease in relative proportion of Lactobacilli and E. coli of stressed mice (0.53 ± 0.63 vs 1.14 ± 1.07, P <0.05), while there was no significant difference in the anaerobes (Lactobacilli) between the two groups (2.31 ± 0.70 log10 CFU / g vs. 2.44 ± 0.37 log10 CFU / g, P> 0.05). D-xylose concentrations in plasma in psychological stress mice were significantly higher than those in the control group (2.90 ± 0.89 mmol / L vs 0.97 ± 0.33 mmol / L, P <0.01). CONCLUSION: Small intestinal dysfunction under psychological stress may be related to the small intestinalmotility disorder and dysbacteriosis and the damage of mucosa probably caused by psychological stress.