Fig. 3

Effects of opioid and adrenergic receptor antagonists on EA-induced anti-allodynic action in oxaliplatin-injected rats. The behavioral tests for cold allodynia were performed before the i.p. injection of the drugs [a Normal Saline control (n = 8), b; Naloxone (n = 8), c; Phentolamine (n = 8)] and after the EA stimulation (2 Hz, ST36 acupoint, 0.3-ms pulse duration, 0.2–0.3 mA, for 20 min). Each drugs without EA stimulation had no significant effect on cold allodynia signs. d Plasma β-endorphin levels were significantly increased at 10 min after the end of EA stimulation as compared to the control (no EA) condition, and subsequently decreased at 120 min post-EA (n = 4/group). e Time course of anti-allodynic actions of morphine (2 mg/kg, i.p., n = 8), 20 min (n = 8) or 30 min (n = 8) EA stimulation, and saline control (n = 9) in oxaliplatin-injected rats. Data are presented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 by paired t test (a–c) or one-way ANOVA followed by Dunnet’s test (d, e)