en Pain and addiction Neurophysiology/Pharmacology Experimental research article Experimental research article Introduction: Several investigations have indicated that dopamine D receptors could influence morphine 2 eward. The influence of olanzapine (a D dopamine receptor antagonist) on the morphine-induced conditioned 2 lace preference (CPP) in male and female mice was investigated in the present study. Methods: The effects of olanzapine on the acquisition and expression of morphine CPP in male and female -MRI mice (W: 20-25 g) were investigated in the present study. Resultd: Subcutaneous (s.c.) injection of morphine (1-10 mg/kg, three drug sessions) induced place preference oth in male and female mice. Intraperitoneal (i.p.) administration of olanzapine (0.5-5 mg/kg) induced place version (CPA) in female mice but not in male mice. Administration of olanzapine (1, 2.5, 5 mg/kg, i.p.) reduced oth the acquisition and expression of morphine-induced CPP in male and female mice. However, olanzapine (5 g/kg, i.p.) caused more than 80% mortality in female but not male mice. The effects of olanzapine were reversed y L-arginine (20 mg/kg, i.p.) pre-administration. Conlusion: We conclude that olanzapine reduced morphine effects via different mechanism/s. Morphine; Olanzapine; Place preference; Nitric oxide; Mice. 135 142 http://ppj.phypha.ir/browse.php?a_code=A-10-74-3&slc_lang=en&sid=1 Parivash Hafez-Amini 320031947532846002918 320031947532846002918 No Jamal Shams 320031947532846002919 320031947532846002919 No Ali Shabahng-Saber-Tehrani 320031947532846002920 320031947532846002920 No Ali Haeri-Rohani 320031947532846002921 320031947532846002921 No Kazem Parivar 320031947532846002922 320031947532846002922 No Vahab Babapour 320031947532846002923 320031947532846002923 No Hedayat Sahraei h.sahraei@bmsu.ac.ir 320031947532846002924 320031947532846002924 Yes