Figure 2.

Baseline latency (Panel A) and %MPAE (Panel B) during 15 days of chronic morphine treatment. Two groups of rats were used. One group received saline (1 ml/kg) as control while the other group received morphine (10 mg/kg) for 15 days. The animals in each group were tested on days 1, 5, 10 and 15 of the injections to explore morphine-induced hyperalgesia and tolerance. Each point in panel (A) represents mean ± SEM of baseline latencies in each experimental group but in panel (B) it represents %MPAE of each group on the respective day. *** P<0.001 compared to the saline-treated group on the respective day. +++ P<0.001 compared to the morphine-treated group on the first day of the injections