Figure 5

Cross-tolerance development to morphine in morphine, methadone or buprenorphine prenatally exposed rats. (A) Tail-flick latency and the area under the curve (AUC) in animals after receiving the first injection of morphine, 10 mg/kg, s.c. (B) Tail-flick latency and the AUC in animals after receiving the 7th injection of morphine, 10 mg/kg, s.c. All data are expressed as mean ± S.E.M, (N = 9 in prenatally methadone and buprenorphine exposed group; N = 19 in prenatally morphine and saline exposed group), *p < 0.05, ***p < 0.001 compared to saline control; ⁺⁺P < 0.01, ⁺⁺⁺P < 0.001 compared to morphine; ^#P < 0.05, ^##P < 0.01 compared to methadone.