Functional expression of adrenergic and opioid receptors in Xenopus oocytes: interaction between α2- and β2-adrenergic receptors

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We functionally expressed α2-adrenergic, β2-adrenergic, and δ-opioid receptors in Xenopus laevis oocytes. We detected receptor function as changes in currents carried by adenosine 3′,5′-cyclic monophosphate (cAMP)-regulated chloride channels provided by the cystic fibrosis transmembrane conductance regulator (CFTR) and recorded by two-electrode voltage clamp. Co-application of forskolin and isobutylmethylxanthine (IBMX) or IBMX alone produced currents with a reversal potential indicative of chloride ions only in oocytes previously injected with mRNA encoding CFTR. Isoproterenol produced concentration-dependent responses in oocytes injected with mRNA encoding β2-adrenergic receptors and CFTR, and co-administration of propranolol antagonized these responses. Similarly, the α2-adrenergic agonist UK14304 increased IBMX-induced currents only in oocytes injected with mRNA encoding α2-adrenergic receptors and CFTR, and idazoxan antagonized these enhancements. The δ-opioid agonist DADLE produced concentration-related, naloxonc-reversible increases in IBMX- and forskolin-induced currents only in oocytes injected with mRNA encoding δ-opioid receptors and CFTR. In oocytes co-injected with α2, β2, and CFTR mRNAs, isobolographic analysis revealed an additive interaction between α2 - and β2-adrenergic receptors. These studies establish the oocyte as a cell system for studying the interactions among cAMP-modulating G protein-coupled receptors and provide another example of alternative coupling of α2-adrenergic and δ-opioid receptors to G proteins, possibly Gs proteins, other than Gi proteins.

Original languageEnglish (US)
Pages (from-to)72-80
Number of pages9
JournalMolecular Brain Research
Issue number1
StatePublished - Jan 1995


  • Adenylyl cyclase
  • CFTR
  • Cystic fibrosis transmembrane conductance regulator
  • Protein kinase A
  • cAMP
  • α Adrenoceptor
  • β Adrenoceptor
  • δ Opioid receptor


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