Assessment of the role of NMDA receptors located in hippocampal CA1 area on the effects of oral morphine dependency on spatial learning and memory in rat

Introduction: It has been reported that oral morphine dependency facilitated formation of spatial learning and memory. In the present study the role of NMDA receptors located in hippocampal CA1 area of morphine dependent rats was studied. Methods: Male rats were divided into 4 groups. Two cannulae were stereotaxically implanted bilaterally into the hippocampal CA1 area. After 5 days recovery, animals received morphine sulfate or sucrose for 30 consecutive days in drinking water. Morris water maze (MWM) studies were performed from day 26 to 30. In the above mentioned days, animals received bilateral intrahippocampal CA1 area injection of 3.7μg/0.5μl D,L-AP5 (NMDA receptors antagonist) or 0.5μl saline, 30 min before daily experimentation. Spatial learning and memory parameters were subjected to the analysis of variance (ANOVA). Results: Morphine dependence potentiated spatial learning and memory parameters using MWM. D,L-AP5 could inhibit formation of spatial learning and memory in both control and dependent group. Conclusion: Activation of NMDA receptors located in hippocampal CA1 area is essential for potentiation of spatial learning and memory in morphine dependence rats.