Expression of EAAC1 in dorsal root ganglion in rats with inflammatory pain-morphine tolerance

Objective To explore the role of excitatory amino acid carrier 1(EAAC1)in dorsal root ganglion(DRG) in the mechanism of developing morphine tolerance.Methods Thirty male SD rats were implanted intrathecal catheters and randomized into 6 groups with 5 rats each.The rats of 4 groups were made into the model of adjuvant-induced arthritis in the left hind limb and were administered intrathecally,morphine 10 μg(group M10),morphine 20 μg(group M20),morphine 20 μg plus naloxone 10 μg(group MN),or saline(group C) respectively.The other 2 groups without were administered intrathecally saline(group C0) or morphine 20 μg(group M0).The drugs were administered twice daily for 7 days.Mechanical withdrawl threshold(MWT) of the left hind limb was examined to evaluate the behavior.Immunohistochemistry was used to detect the expression of EAAC1 in the left L3-4 and L4-5 DRG.Results Morphine tolerance was formmed stably in the arthritis rats of group M10 and group M20 after administering morphine for 7 days.The expression of EAAC1 in DRG was downregulated.Conclusion DRG EAAC1 may be involved in the mechanism of developing morphine tolerance in rats with inflammatory pain.