Electroacupuncture alleviates stress-induced visceral hypersensitivity through an opioid system in rats

Figure 3 Heterotypic intermittent stress increased abdominal withdrawal reflex scores to colorectal distention. A: Abdominal withdrawal reflex (AWR) scores were used as a function of distention pressure (20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg). Heterotypic intermittent stress (HIS) significantly enhanced AWR scores measured at 6 h and 24 h after termination of last stressor when compared with baseline (Pre) under 20 mmHg, 60 mmHg and 80 mmHg distention pressure, while HIS significantly enhanced AWR scores measured at 6 h after termination of last stressor when compared with Pre group under 40 mmHg distention pressure [Tukey post hoc test following Friedman analysis of variance (ANOVA)]. Therefore, HIS can enhance visceral hypersensitivity in rats at 6 h and 24 h after termination of last stressor generally when compared with baseline (Pre). AWR scores returned to normal level 48 h after termination of last stressor (n = 8 rats for each group; ^aP < 0.05 vs Pre); B: HIS remarkably reduced distention threshold. Distention threshold was the minimal distention pressure to evoke abdominal movement. In agreement with AWR scores, distention threshold started to reduce at 6 h and maintained at a low level at 24 h and returned to normal level 48 h after termination of last stressor (Friedman ANOVA followed by Tukey post hoc test, n = 8 rats for each group; ^aP < 0.05 vs Pre).