Muscarinic receptors modulate the mRNA expression of NMDA receptors in brainstem and the release of glutamate in periaqueductal grey during morphine withdrawal in rats / 生理学报

The antisense approach and RT-PCR were used to study the effects of muscarinic receptors on the scores of morphine-withdrawal syndrome and the expression of NMDA receptor subtypes (NR(1A) and NR(2A)) mRNA in rat spinal cord and brainstem. The concentrations of glutamate in periaqueductal grey (PAG) of morphine-withdrawal rats were determined by capillary electrophoresis with laser-induced fluorescence detection. The data showed that the NR(1A) and NR(2A) mRNA levels were increased significantly in the spinal cord and brainstem 1 h after the injection of naloxone (4 mg/kg, i.p.) in morphine-dependent rats. Moreover, in morphine-dependent rats pretreated (i.p.) with scopolamine (0.5 mg/kg), or pirenzepine (10 mg/kg), MK801 (0.125 mg/kg), L-N-nitroarginine methylester (10 mg/kg) 30 min before naloxone injection, the NR(1A) and NR(2A) mRNA levels were significantly lower than those of 1 h morphine-withdrawal rats. Intrathecal injection of NR(1A) or M(2) receptor antisense oligonucleotides (A-oligo, 4 microg/per rat) 24 h prior to naloxone challenge could block the morphine withdrawal symptoms including wet dog shaking, irritability, salivation, diarrhea, chewing and weight loss. Meanwhile, in morphine-dependent rats the NR(1A) mRNA levels in the spinal cord and brainstem were down-regulated by intrathecal injection of M(2) receptor A-oligo. The glutamate concentrations in PAG microdialysis were increased to a maximal level 15 min after naloxone injection. The glutamate response was inhibited by pretreatment with M(2) receptor A-oligo but not by M(1) A-oligo. The results suggest that the expression of NMDA receptors and the release of glutamate in brainstem are involved in the processes of morphine withdrawal and that the NMDA receptor expression is possibly regulated by the muscarinic receptors during morphine withdrawal.

mRNA expression of muscarinic receptors in spinal cord and brainstem in morphine dependent rats / 药学学报

<p><b>AIM</b>To observe mRNA expression of muscarinic acetylcholine receptors in spinal cord and brainstem in morphine dependent or withdrawal rats.</p><p><b>METHODS</b>The mRNA expression level of m1, m2, m3, m4 and m5 were determined by RT-PCR, the beta-actin mRNA expression was used as internal control.</p><p><b>RESULTS</b>The mRNA level of m1, m2, m3, m4 and m5 in spinal cord and m1 and m2 in brainstem were increased significantly during morphine dependence, and the levels of m1, m2, m3 and m4 in spinal cord and m1 in brainstem were decreased 1 h after the injection of naloxone (4 mg.kg-1, i.p.) in morphine dependent rats. Either scopolamine (0.5 mg.kg-1) or pirenzepine (10 mg.kg-1) was shown to significantly decrease the morphine withdrawal symptoms in rats. The levels of m1, m2, m3 and m5 in spinal cord were increased by pretreatment with pirenzepine and the levels of m2, m3 and m4 in spinal cord were increased by pretreatment with scopolamine.</p><p><b>CONCLUSION</b>The adaptive expression of muscarinic receptors at spinal and supraspinal levels play important role in mediating morphine dependence and withdrawal in rats.</p>

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

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.