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Modification by Cholecystokinin Octapeptide of the Binding ofμ‐, δ‐, and K ‐Opioid Receptors
Author(s) -
Wang XiaoJing,
Han JiSheng
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb03149.x
Subject(s) - etorphine , cholecystokinin , chemistry , receptor , proglumide , enkephalin , cholecystokinin receptor , opioid , agonist , medicine , endocrinology , opioid peptide , opioid receptor , antagonist , stereochemistry , (+) naloxone , biochemistry , biology
Previous study has shown that cholecystokinin (CCK) octapeptide (CCK‐8) suppressed the binding of opioid receptors to the universal opioid agonist [ 3 H]etorphine. In the present study, highly selective tritium‐labeled agonists for the μ‐ {[ tyrosyl ‐3,5‐ 3 H][d‐Ala 2 ,MePhe 4 ,Gly‐ol 5 ]enkephalin ([ 3 H]DAGO)}, δ‐ {[ tyrosyl ‐3,5‐ 3 H][d‐Pen 2,5 ]enkephalin ([ 3 H]DPDPE)}, and k ‐ ([ 3 H]U69,593) opioid receptors were used to clarify which type(s) of opioid receptor in rat brain homogenates is suppressed by CCK‐8. In the competition experiments, CCK‐8 suppressed the binding of [ 3 H]DAGO and [ 3 H]U69,593 but not that of [ 3 H]DPDPE to the respective opioid receptor. This effect was blocked by the CCK antagonist proglumide at 1 μmol/L. In the saturation experiments. CCK‐8 at concentrations of 0.1 nmol/L to 1 μmol/L decreased the B max of [ 3 H]DAGO binding sites without affecting the K D ; on the other hand, CCK‐8 increased the K D of [ 3 H]U69,593 binding without changing the B max . The results suggest that CCK‐8 inhibits the binding of μ‐ and K ‐opioid receptors via the activation of CCK receptors.