Background: Considering the increased activity of hippocampal glial cells due to chronic morphine administration and the involvement of hippocampus in restoration of the addictive drug-associated experience, the role of these cells on morphine induced conditioned place preference (CPP) was investigated.

Materials and Methods: In this experimental study, four groups of animals were evaluated. After habituation to CPP apparatus on the first day, conditioning was done by injection of morphine (5 mg/kg) or its vehicle (saline) during three consecutive days. On the fifth day, the time spent in each compartment of CPP cage and locomotor activity was recorded for 20 min. To investigate the role of hippocampal glial cells in CPP, these cels were inbibited by bilaterally injecting fluorocitrate (1nmol/1ml), before each morphine injection. CPP testing in this group and animals received fluorocitrate vehicle (Phosphate buffer saline) was done before morphine injection.

Results: Fluorocitrate pretreatment reduced morphine induced conditioned place preference acquisition, so that a significant decrease was observed in conditioning score (unpaired t-test, p<0.01) in this group (n=8) compared to animals received morphine (n=9). Neither morphine nor fluorocitrate pretreatment did not affect locomotor activity (ANOVA, p>0.05).

Conclusion: The results suggest that glial cells in the hippocampus are involved in morphine induced conditioned place preference.