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

Figure 4 Heterotypic intermittent stress enhanced electromyographic activities in response to colorectal distention. Electromyographic (EMG) activities in the external oblique muscle in response to graded colorectal distention (CRD) were measured before stress and 6 h, 24 h, 48 h and 7 d after termination of heterotypic intermittent stress (HIS). The magnitude of EMG activity was expressed as area under curve (AUC). A: Examples of EMG activities recorded from baseline (Pre), 6 h, 24 h, 48 h and 7 d after termination of HIS in rats responding to distention pressures of 20 mmHg, 40 mmHg and 80 mmHg; B: Bar graph shows the changes in average of AUC before and after HIS protocol. There was no significant difference between EMGs of different time points at 20 mmHg. The magnitude of EMG activity of 6 h, 24 h and 48 h was significantly larger than that of Pre at distention pressures of 40 mmHg, 60 mmHg and 80 mmHg (Tukey post hoc test following two-way repeated measures analysis of variance, n = 6 rats for each group; ^aP < 0.05 vs Pre).