Effects of NR2B antisense oligonucleotide on expression of μ and κ opiate receptor in spinal and brainstem during morphine dependence and withdrawal in rats

Abstract

Objective To observe the effects of NR2B antisense oligonucleotide (ANR2B) on gene expression of μ and κ opiate receptor in spinal cord and brainstem during morphine dependence and withdrawal in rats.To explore the interaction between NR2B subunits of N -methyl-D-aspartic acid (NMDA) receptors,and μ,κ＜ opioid receptors,in the process of mediating morphine dependence and tolerance.Methods Animals were male Sprague Dawley rats weighing 230 g-270 g.Animal models of morphine dependence were established by repeated subcutaneous injection of morphine with progressive doses.Animal models of urged withdrawal in morphine dependence were established by single intraperitoneal injection of naloxone,to morphine dependence rat.After making sure of the successful animal models,40 rats with an intrathecal tube were randomly divided into 5 groups,8 in each group.Group A:the morphine dependence group.Group B:control group.Group C:the morphine withdrawal group.Group D:ANR2B intrathecally injected at the same time of subcutaneous injection of morphine.Group E:intrathecal injection of ANR2B 30mi n before injection of naloxone.The mRNA levels of μ and κ opiate receptor in spinal cord and brainstem were assayed by reverse transcription polymerase chain reaction with the beta-actin mRNA as an internal control.Results Increase in NR2B mRNA expression in the spinal cord and brainstem induced by morphine were significantly attenuated by ANR2B(0.965±0.012,0.958±0.020).The total score of morphine-withdrawal symptoms were significantly decreased by spinal administration of NR2B antisense oligonucleotide (32±2,22±3).The mRNA levels of μ opiate receptor increased significantly in spinal cord and brainstem (0.955±0.021,0.946±0.013)during morphine dependence.But μ opiate receptors mRNA levels decreased after injection of ANR2B (0.801±0.013;0.824±0.021)during morphine withdrawal in rats.The mRNA levels of κ opiate receptor changed conversely compared with the μ opiate receptor during morphine dependence and withdrawal.Spinal administration of NR2B antisense oligonucleotide at the same time of injection of morphine reversed the change tendency of μ and κ opiate receptor in spinal cord and brainstem during morphine dependence and withdrawal in rats.Changes had no statistic significance in spinal administration of NR2B antisense oligonucleotide 30min before injection of naloxone,compared with the withdrawal group.Conclusion The expression of μ and κ opiate receptor in spinal cord and brainstem plays an important role in mediating the development of morphine dependence and withdrawal.NR2B antisense oligonucleotide reversed the expression of μ and κ opiate receptor in spinal cord and brainstem during morphine dependence and withdrawal in rats.It suggests that NR2B antisense oligonucleotide can inhibit the development of morphine dependence and attenuate morphine-withdrawal symptoms by mediating the expression of μ and κ opiate receptors. Key words: Morphine dependence; NR2B antisense oligonucleotide; μ opiate receptor; κ opiate receptor