Expression of ? and ? opiate receptor in spinal cord andbrainstem during morphine withdrawal in rats / 中国临床药理学与治疗学

ABSTRACT

Aim To observe the gene expression of ? and ? opiate receptor in spinal cord and brainstem,and the effects of muscarinic receptor antagonist, NMDA receptor antagonists and inhibitor of nitric oxide synthase on the expression of these genes during morphine withdrawal in rats. Methods The mRNA levels of ? and ? opiate receptor mRNA were assayed by reverse transcription polymerase chain reaction (RT_PCR) with the beta_actin mRNA as an internal control. Results The ? opiate receptor mRNA levels were increased significantly in spinal cord and brainstem during morphine dependence, and decreased after injection of naloxone during morphine withdrawal in rats. The ? opiate receptor mRNA levels in spinal cord and brainstem were changed conversely compared with the ? opiate receptor mRNA levels during morphine dependence and withdrawal. The ? and ? opiate receptor mRNA levels in spinal cord and brainstem were decreased by administration of either Rp_cAMPs or calyculin A while these levels were not changed by Sp_cAMPs at half hour before injection of naloxone in morphine dependent rats. Administration of l_N_nitric arginine methylester(10 mg?kg-1) resulted in a decrease of ? opiate receptor and ? opiate receptor levels in spinal cord , and ? opiate receptor levels in spinal cord and ? opiate receptor levels in brainstem were dedcreased by pretreatment with methyl_scopolamine (0.5 mg?kg-1) during morphine withdrawal. However, the ? and ? opiate receptor levels in both spinal cord and brainstem were not different from those of morphine withdrawal rats pretreated with either MK801 (0.125 mg?kg-1) or pirezenpine(10 mg?kg-1). In adddition, ?_actin mRNA levels were not different in each group.Conclusion The expression of ? opiate receptor and ? opiate receptor mRNA plays an important role in mediating the process of morphine dependence and withdrawal, and the expression of ? opiate receptor and ? opiate receptor mRNA in spinal cord and brainstem could be inhibited by block of muscarinic receptor or inhibition of nitric oxide production.