Table 4.

Effects of thymoquinone on the expression of tolerance to analgesic effects of morphine in mice

Drug (dose)	Hot-plate latency (s)
Control	14.48 ± 1.62
Morphine (10 mg/kg), day 1	34.35 ± 3.47 ***
Morphine (10 mg/kg), day 4	9.68 ± 1.29
Thymoquinone (10 mg/kg)	10.22 ± 1.98
Thymoquinone (20 mg/kg)	17.32 ± 2.35
Thymoquinone (40 mg/kg)	24.27 ± 4.17 **

Thymoquinone and control were administered intraperitoneally 30 minutes before the injection of the last dose of morphine (10 mg/kg, i.p.) on the fourth day. Control: Normal saline + Tween 80 (0.8%, v/v); Values are the mean ± SEM for 7 mice;

^**p<0.01,

^***p<0.001, as compared to control;

p<0.01, as compared to morphine day 4.