Figure 1.

Bifidobacterium longum (B.longum) colonized the ileum terminal epithelium and alleviated visceral sensitivity in water avoidance stress (WAS) rats. The WAS model was produced by placing rats on a block (10 × 8 × 8 cm) in the middle of a plastic tank at 8:00–9:00 o’clock every morning for 10 days. The B. longum group was administered 1 × 10⁹ CFU B. longum for 10 days, whereas rats in the control group were given normal saline. (a) Scanning electron microscopy indicated that B. longum could colonize the mucosa of the terminal ileum after oral administration. Scale bar = 200 μm. (b, c) Fecal pellet output (FPO) and the proportions of unformed stool were calculated among the three groups. (d, e) The threshold intensity of colorectal distention (CRD) and abdominal withdrawal reflex (AWR) score were evaluated among the three groups (n = 8). The threshold value in the WAS group was significantly decreased, and B. longum significantly increased the threshold. For the AWR, the WAS group showed an increased score at 40 and 60 mmHg pressure, and B. longum administration effectively decreased the AWR under both pressures. However, there was no significant difference in scores among the three groups at 20 and 80 mmHg pressure. (f) Body weight was recorded among the three groups on days 1 and 10. On day 1, the body weight among the three groups did not differ, whereas on day10, the weight of WAS group rats was much lower than that of control group rats; B. longum administration improved the body weight in the B. longum group. The data are shown as the mean ± SD, *, p < .05, **, p < .01, **, p < .001 WAS vs Ctrl and #, p < .05 B. longum vs WAS, n = 8.