Table 3.

Effects of thymoquinone on the induction 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)	15.14 ± 1.95
Thymoquinone (20 mg/kg)	19.75 ± 3.05*
Thymoquinone (40 mg/kg)	22.24 ± 2.96 **

Thymoquinone and control were administered intraperitoneally 30 min before the injection of morphine during the 3-day administration schedule. The last dose of morphine (10 mg/kg, i.p.) was administered on the fourth day. The animals did not received thymoquinone or control on the fourth day. Control: Normal saline + Tween 80 (0.8%, v/v); Values are the mean ± SEM for 7 mice;

^*p<0.05,

^**p<0.01,

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

p<0.05,

p<0.01, as compared to morphine day 4.