摘要：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-Ala2, N-Me-Phe4, Gly5-ol]enkephalin (DAMGO) and [D-Ala2, D-Leu5]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.
