Figure 1.

The effects of different doses of morphine on the place preference paradigm behavior. Animals received morphine (1, 2.5, 5 and 7.5 mg/Kg; SC) during conditioning session and were examined in the test day in drug free state. Non-linear regression was also applied for the calculation of ED50 and the opposite point was calculated as downward point. Data are shown as mean ± SEM for 6-8 rats, *p < 0.05, **p < 0.01 different from the saline control group