Changes in the protein expression of NR2B subunit and CaMK II in hippocampus CA1 of rats with recurrence of CPP induced by morphine

OBJECTIVE To study the changes of the protein expression of NR2B and CaMKII in hippocampus CAl area of rats with recurrence of conditioned place preference (CPP) induced by morphine. METHODS Morphine was administered via subcutaneous injection at constant dose (10 mg·kg~(-1)) for 8 days to establish morphine CPP. The rats were administered saline instead of morphine to induce CPP extinction for 10 days. CPP was reinstated following a single priming injection of morphine (2. 5 mg·kg~(-1)). The morphine induced rat CPP acquisition, extinction and reinstatement model was established. The protein levels of NR2B subunit and CaMK Ⅱ in hippocampus CAl of rats with CPP recurrence of rats were measured by streptavidin- perosidase immunohistochemical method and the mean gray values of immunoreactive product was detected by image analysis system. RESULTS Injecting morphine (10 mg·kg~(-1)) for 8 days succeeded to induce CPP. After 10 days training with saline, CPP failed to be induced. A single priming injection of morphine(2. 5 mg/kg)kindled CPP. During CPP reinstatement, the expression of NR2B subunit and CaMKⅡ in hippocampus CA1 increased significantly compared with the saline group (P0. 05). CONCLUSION The increased expression of NR2B subunit and CaMK Ⅱ in hippocampus CAl of rats involves in CPP recurrence induced by morphine.