[ 3H]U-69593 a highly selective ligand for the opioid κ receptor

The selective κ agonist U-50488 was recently discovered and characterized. In this study, the receptor binding properties of [ 3H]U-69593, an analog of U-50488, were characterized. [ 3H]U-69593 binds with high affinity (3 nM) to membranes prepared from guinea pig, mouse and rat brain. The number of κ binding sites comprise only 13%, 9% and 4% of the total opioid sites, respectively. The benzmorphans, dynorphin, and compounds structurally related to U-50488 have high affinity for this κ site.