Expression of NMDA receptor subunit 2A in the spinal cord of morphine tolerant rats / 中华行为医学与脑科学杂志

ObjectiveTo study the distribution and expression of NMDA receptor subunit 2A in the spinal cord of morphine tolerant rats. MethodsTwelve Sprague-Dawley rats were randomly divided into two groups with 6 rats each: control group (C) were intrathecally administrated 0.9% NaCl 10μl and morphine group(M) received 10μg morphine (i.t.). Drugs were administrated twice daily for 7 consecutive days. Tail flick latency (TFL) in the hot water immersion test was used to evaluate changes of thermal hyperalgesia latency of each group before and 30min after administration every morning. Rats were killed the day after last administration and L4～5 segment of the spinal cord was removed for determination the expression of NR2A by immunofluorescence method. ResultsTFL of group M was decreased gradually after chronic administration of morphine intrathecally. There was no significant difference between group M[(3.25±0.93)s] and group C[(2.66±0.27)s] on the 7th day (P＞0.05). A morphine tolerant model was established successfully. NR2A was distributed throughout the rat spinal cord. The expression of NR2A in group M(OD:9617±1233) was increased compared with group C(OD:2.66±0.93) (t=3.133,P＜0.05).ConclusionThe expression of NR2A was upregulated after repeated administration of morphine intrathecally in the superficial dorsal horn of spinal cord of morphine tolerant rats,which may be part of the mechanisms of morphine tolerance.

INFLUENCE OF PARTIALLY C-TERMINAL DELETION OF NR2A SUBUNITS ON THE SURFACE EXPRESSION AND FUNCTION OF NMDA RECEPTOR CHANNELS / 解剖学报

Objective To investigate whether the partially C-terminal deletion of NR2A subunit alters the surface expression and channel function of NMDA receptors in both HEK293 cells and cultured hippocampal neurons of rats. Methods Four plasmids for NR2A mutants with N-terminally GFP-tagged and C-terminal deletion NR2A?C1(?897L-1017S),NR2A?C2(?1024D-1142P),NR2A?C3(?1149D-1347G),and NR2A?C4(?1354S-1464V) were generated,and transfected into HEK293 cells and hippocampal neurons in culture.Surface staining was performed using anti-GFP antibody and Cy3 conjugated secondary antibody.Glutamate evoked currents were also detected using whole-cell recording. Results Positive surface staining was found for all the HEK293 cell co-transfected NR1-1a/NR2A?C1,NR1-1a/NR2A?C2,NR1-1a/NR2A?C3 or NR1-1a/NR2A?C4,and quantitative analysis showed no significant decrease in surface expression level when compared to that from NR1-1a/NR2A transfection.Glutamate-evoked currents were recorded in HEK293 cells co-transfected with NR1-1a/NR2A?C2 or NR1-1a/NR2A?C4.Surface expression level of NMDA receptor clusters on dendrites was significantly decreased in the neurons transfected with NR2A?C1,NR2A?C2 or NR2A?C3 than in those transfected with NR2A.Conclusion C-terminal deletion of NR2A subunit differentially effects surface expression of NMDA receptors in HEK293 cells and in hippocampal neurons in culture.