Aims: Facing maternal separation during early postnatal life leads to disturbances in the cognitive and neuro-chemical activities of the brain. The aim of this study was to investigate the effects of maternal separation on spatial learning and memory of morphine-dependent rats.

Materials and Methods: This experimental study was carried out on 40 male Wistar rats of 45 days old. Animals were divided into control group (CO), morphine dependent (MD) and 3 group of rats which maternally separated during 1 (MS1), 2 (MS2) and 3 weeks (MS3) after birth. Except CO rats, the other groups were subcutaneously injected 10 mg/kg morphine every 12 hours for 10 days. At the 11th day signs of withdrawal syndrome were evaluated and during next 4 consecutive days spatial learning was evaluated by Morris water maze (MWM). The rats’ spatial memory retrieval was also estimated at the last day.

Findings: Although morphine dependence did not affects spatial learning and memory of rats, but 3 weeks maternal separation caused the animals spend more time and travel more distance to find the hidden platform than to CO group (P<0.001 for both of comparisons). Also, they spent less time and passed less distance in the target quadrant in probe trial (P<0.001 for both of comparisons).

Conclusion: In conclusion, maternal separation impairs spatial learning and memory of rats.