Previous experiments resolved four κ binding sites in guinea pig brain termed κ1a, κ1b, κ2a, and κ2b. The present study was undertaken to examine the occurrence of κ receptor sybtypes in rat and human brain. [3H]U69,593 and [3H]bremazocine were used to label κ1 and κ2 binding sites, respectively, present in brain membranes depleted of μ and δ binding sites by pretreatment with the irreversible ligands, BIT and FIT. Low levels of [3H]U69,593 binding precluded a detailed quantitative study of κ1 binding sites in these species. Quantitative examination of [3H]bremazocine binding resolved two κ2 binding sites in both rat and human brain whose ligand selectivity patterns differed from that of the guinea pig. These observations suggest that there may be considerable variation in the ligand recognition site of κ receptor subtypes among mammalian species.
- Kappa receptors
- Ligand binding studies
- Opioid receptors
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience