Figure 3.

Analgesic effects of different doses of morphine on hot plate test in tolerant rats. Five groups of rats with a history of 14 days injection of morphine (10 mg/kg) were used. On day 15, first, baseline latency was recorded for each rat, then one group of the animals received saline (1 ml/kg) while the other groups received different doses of morphine (0.1, 1, 5 and 10 mg/kg), and 30 min later all groups were tested on the hot plate to examine test latency. Each bar represents mean ± SEM related to %MPAE of each group. * P<0.05 compared to the saline-treated group