Interaction between NMDA receptor subunit 2B and metabotropic glutamate receptor 5 in the spinal cord of morphine-tolerant rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the interaction between NMDA receptor subunit 2B (NR2B) and metabotropic glutamate receptor 5 (mGluR5) in the spinal cord of morphine-tolerant rats. Methods Sixteen male SD rats weighing 220-280 g were randomly divided into 2 groups with 8 rats in each group control group (C) and morphine group (M). In group M morphine 10μg was administered intrathecally (IT) twice a day for 7 consecutive days. In group C equal volume of normal saline was given instead of morphine. Tail flick latency (TFL) (a segment of tail 4-5 cm long was immersed in 52-53℃ hot water) was used to measure the antinocicepitve effect of morphine before and 30 min after morphine administration every morning. MPE (percentage of maximal possible effect) was calculated (pain threshold after drug administration - baseline pain threshold)/(10- baseline pain threshold)× 100% . The animals were killed at the next day after last IT administration and the dorsal half of L4-5 spinal cord was isolated and homogenized for determination of NR2B and mGluR5 protein expression by Western blot and CO-IP. Results MPE was significantly increased at 1-5 d of drug administration and returned to baseline at 7 d in group M as compared with group C. The mGluR5 protein expression was significantly up-regulated in group M as compared with group C but there was no significant difference in NR2B protein expression between the 2 groups. Conclusion There is interaction between NK2B and mGluR5 in the spinal cord of morphine-tolerant rats.