The role of NO in the CA3 region of hippocampus on learning and spatial memory in male morphine dependent rats

Drug of abuse causes tolerance and dependency in brain and diversity of behavioral and cognitive deficiency. The effect of morphine dependency on learning and spatial memory is controversial. So in this study role of NO in CA3 region of hippocampus on learning and spatial memory in normal and morphine dependent rats was investigated. After anaesthetization of male rats, cannulae is implanted bilaterally in CA3 region of hippocampus via the stereotaxic instrument. After recovery period (7 days), animals divided in the normal and morphine dependent groups. Then normal group of animals divided in 4 subgroups that received 1μl saline (Sham), L-Arginine (63 or 3μg/rat), L-Name (71μg/rat), centrally. Morphine dependent group divided in 3 subgroups that received 1μl saline (Sham), L-Arginine (63 μg/rat), L-Name (71μg/rat), centrally. Two groups were control and morphine dependent that only cannulated. 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 the test period (5 days) that animals were trained in morris water maze to evaluate learning and spatial memory. Results showed that in normal rats L-Name(NOs inhibitor) decreased learning and spatial memory and 3μg/rat of L-Arginine(precursor of NO) improved learning and spatial memory. Morphine dependency decreased spatial memory but it did not affect learning. In morphine dependent animals both L-Name and L-Arginine decreased learning but did not affect spatial memory. So morphine dependency could prevent the improving effect of NO on learning and spatial memory in CA3 of hippocampus.