Expression of GLAST in spinal cord dorsal horn of arthritis rats with chronic morphine tolerance

Objective: To construct the rat model of arthritis-chronic morphine tolerance based on the adjuvant-induced arthritis model,observe the change of expression of GLAST in spinal cord dorsal horn of rats with chronic arthritis-morphine tolerance,and analyze the effect of GLAST on the development of morphine tolerance.Methods:The 36 healthy male SD rats were randomized into 6 groups and were implanted intrathecal catheters.Amongst,the rats in four groups were made into model of adjuvant-induced arthritis and were administered intrathecally saline(group A),morphine 10 μg.kg-1(group B),morphine 20 μg.kg-1(group C),morphine 10 μg.kg-1 + naloxone 10 μg.kg-1(group D),respectively.The rats in the other two groups without arthritis were administered intrathecally saline(group E),morphine 20 μg.kg-1(group F),respectively.The drugs were administered twice daily for 7 days.Mechanical withdrawl threshold(MWT) of rats was examined to evaluate its behavior.Immunohistochemistry was used to detect the expression of GLAST in spinal cord dorsal horn.Results: Morphine tolerance was formmed stably in the arthritis rats of group B and group C after administering morphine for 7 days.The expression of GLAST in spinal cord dorsal horn was downregulated.Conclusion: Spinal GLAST may contribute to the development of morphine tolerance in rats with inflammatory pain.