The effect of morphine dependence on expression of hippocampal N-methyl-D-aspartate receptor subunits in male rats

Introduction: N-methyl-D-aspartate (NMDA) receptors play a pivotal role in the development of tolerance and physical dependence to opiates. Activation of NMDA receptors involves the induction of long term potentiation (LTP) in hippocampus. Our previous study suggested that chronic oral administration of morphine enhanced NMDA dependent LTP in the CA1 area of hippocampal slices of rats. The present study examines the expression levels of individual NMDA receptor subunits, NR1, NR2A and NR2B, in the hippocampus of morphine-dependent rats by using western blotting. Methods: Total proteins of hippocampus were extracted by Tris-HCl buffer containing anti proteases and sodium dodecyl sulfate (SDS). The extracted proteins were resolved by SDS-PAGE and transferred to polyvinylidenefloride (PVDF) membrane by tank blotting and the subunits of NMDA receptor were analyzed by immunoblotting by using specific antibodies. Results: Obtained results provide both biochemical and statistical evidence to suggest that NMDA receptor function in the hippocampus, at least in terms of expression of NR1, NR2A and NR2B protein subunits, increases in morphinedependent rats. Conclusion: Taken together, these data support several studies in the literature indicating that NMDA receptors in the hippocampus are involved in the process of opiate dependence.