Background: We previously reported that oral morphine dependence facilitated formation of spatial learning via activation of NMDA receptors located in hippocampal CA1 area. Also, it has been previously reported that intracellular NO signaling pathway is fundamental mechanism by which NMDA receptors exert most of their physiological functions. So, in the current study the interaction of NMDA/NO pathway on above mentioned phenomenon was investigated.
Methods: In this study, morphine dependent rats received bilateral injection of D,L-AP5 (3.7 µg/side) or L-NAME (1.5µg/side) in hippocampal CA1 area as NMDA receptors or nitric oxide synthase (NOS) inhibitors respectively. Morris water maze (MWM) studies were performed to evaluate spatial learning and memory. Data were subjected to the ANOVA and followed by Tukey test for multiple comparisons.
Results: Data showed that formation of spatial learning was completely blocked in both experimental groups with respect to control ones, but there was no any significant difference between function of animals received D,L-AP5 or L-NAME in MWM.
Conclusion: It can be concluded that NMDA receptors exert their action on facilitation of spatial learning in morphine dependent rats basically via activation of intracellular NO signaling pathway.