Abstract: ِIntroduction: The effect of morphine dependency on learning and spatial memory is controversial. So in this study effect of co-administeration of nitric oxide (NO) and morphine in CA3 of hippocampus on learning and spatial memory in morphine dependent rats was investigated. Methods: After anaesthetization of male rats, cannulae implanted bilaterally in CA3 of hippocampus. After recovery period (7 days), morphine dependency induced then animals divided in 6 groups that received 1μl saline (Sham), L-Arginine, L-Name and morphine individually and L-Arginine with morphine or L-Name with morphine individually. Morphine dependency was induced by subcutaneous injection of morphine(10mg/kg first day and 20mg/kg for four days). Last dose of morphine(20mg/kg) was injected daily to maintain morphine dependency during test period (5 days) in morris water maze Results: Results showed that L-Name decreased learning in morphine dependent rats although was ineffective on retention of memory. Morphine did not affect learning and spatial memory. Co-administeration of L-Arginine and morphine not only improved the effect of morphine on learning and memory but also promote the effect of L-Arginine on learning and spatial memory. Conclusion: Thus co-administeration of NO and morphine in morphine dependent rats can improve learning and spatial memory differently from using them individually.

Keywords: Learning, SpatialMemory, Morphinedependency, Hippocampus, NO

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