Effect of opiate on receptor-mediated adenylate cyclase-cAMP signal system in NG-LNCXiNOS cell with the stable expression of inducible nitric oxide synthase gene

Mengwei W. Zang, Qi Shen, Qing Wang, Fei Guo, Jingsheng S. Liu

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

AIM: To study the effect of opiate on receptor-mediated adenylate cyclase (AC)-cAMP signal system in NG-LNCXiNOS cell with the stable expression of inducible nitric oxide synthase gene. METHODS: The intracellular cAMP content was measured with 3H-cAMP protein binding assay. The effect of opioid agonists on binding properties of opioid receptor was assessed using 3H-Etor binding assay with intact cells. RESULTS: The forskolin-stimulated cAMP accumulation was inhibited by opioid agonists in a concentration-dependent manner. The order of inhibitory potencies was DPDPE(D-Pen2, D-Pen5-enkephalin) > DADLE(D-Ala2, D-Leu5-enkephalin) > etorphine > morphine with IC50 values of 2.0 × 10-8, 2.1 × 10-8, 3.7 × 10-8 and 1.7 × 10 mol · L-1, respectively. Such acute inhibitory effect of opioid agonist on adenylate cyclase (AC) activity could be remarkably blocked by the addition of naloxone and completely abolished by pretreatment of the cells with pertussis toxin(PTX), suggesting that acute inhibition of opioid agonists on AC-cAMP system may be regulated via a receptor-mediated and PTX-sensitive G protein pathway. After NG-LNCXiNOS cells were pretreated with DPDPE and DADLE for 48 hours, opioid agonists elevated intracellular cAMP concentration in the presence and absence of naloxone. Chronic exposure of the cells to DPDPE and DADLE resulted in reduction of Bmax values and increase of KD values. Long-term treatment of neuronal cells with opioid agonists and naloxone-precipitated cell "withdrawal" can lead to receptor desensitization in a time-dependent and a dose-dependent manner, and the down-regulation of opiate receptor. CONCLUSION: A cellular model in opioid tolerance and dependence was successfully established. It may be useful for studying the cross-talk regulation of AC-cAMP and NO-cGMP signal pathway on the development of opiate tolerance and addiction.

Original languageEnglish (US)
Pages (from-to)484-490
Number of pages7
JournalYaoxue Xuebao
Volume34
Issue number7
StatePublished - Jul 1 1999
Externally publishedYes

Keywords

  • Drug tolerance
  • Morphine
  • Nitric-oxide synthase
  • Opiate dependence
  • δ-opioid receptor

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology, Toxicology and Pharmaceutics(all)

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