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

Figure 7 Reversal of electroacupuncture-mediated analgesic effect by naloxone. A: The opioid receptor antagonist, naloxone (NLX) (0.1 mg/kg body weight, n = 5), or normal saline (NS) was administrated intraperitoneally 30 min before electroacupuncture (EA) application. Abdominal withdrawal reflex (AWR) scores were recorded immediately after EA termination in rats pretreated with NLX or NS. Both pressure and NLX injection significantly affected the AWRs to colorectal distention in rats [Friedman analysis of variance (ANOVA), P < 0.001 for pressure effect and for NLX injection effect]. Bar graph showed that NLX (0.1 mg/kg body weight) completely blocked the EA-induced analgesic effect when compared with NS treatment at all pressures (Mann-Whitney test following Friedman ANOVA). n = 5 rats for each group. ^aP < 0.05 vs NS-EA group; B: Same dose of NLX treatment did not produce any effect on AWR scores in control rats without EA treatment (Friedman ANOVA). AWRs were only significantly affected by different pressure levels (P < 0.001). n = 5 rats for each group. Control rats were not exposed to heterotypic intermittent stress (HIS).