Inhibitory Effects of NaCl and Guanyl-5'yl-imidodiphosphate (GppNHp) on [^3H]Naloxone Binding to κ-Opioid Receptors in Guinea Pig Cerebellum

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Studies were performed to characterize the opioid receptors in guinea pig brain using the radiolabeled opioid antagonists, [^3H]naloxone and [^3H]diprenorphine and the κ-agonist [^3H]U-69593. The binding of [^3H]U-69593 to guinea pig cerebellar membranes was reduced by NaCl, guanyl-5'-yl-imidodiphosphate (GppNHp) and NaCl + GppNHp, and [^3H]naloxone binding to cerebellar membranes was also reduced by NaCl and GppNHp. In the guinea pig cerebral cortex and striatum and the rat cerebellum, [^3H]naloxone binding was not affected significantly by GppNHp in the presence or absence of 100nM [D-Ala^2,N-Me-Phe^4,Gly^5-ol]enkephalin (DAMGO) and [D-Ala^2,D-Leu^5]enkephalin (DADLE). Guinea pig cerebellar [^3H]diprenorphine binding was not affected by NaCl, GppNHp or NaCl + GppNHp. Furthermore, [^3H]naloxone binding was reduced after pretreating cerebellar membranes with N-ethylmaleimide (NEM), which also attenuated GppHNp-induced inhibition of cerebellar [^3H]naloxone binding. These results suggest that the properties of [^3H]naloxone binding in guinea pig cerebellum differ from those in other brain regions and rat cerebellum, and that the interaction of [^3H]naloxone and [^3H]U-69593,but not [^3H]diprenorphine, with guinea pig cerebellar opioid receptors is associated with a G-protein.
社団法人日本薬学会の論文
1993-09-15