Characterization of NK-3 binding sites in rat and guinea pig cortical membranes by the selective ligand [ 3H]Senktide

Abstract

We have used [ 3H]Senktide, a selective Neurokinin B receptor ligand, for the characterization of NK-3 receptors in rat and guinea pig CNS membranes. Scatchard analysis of saturation binding studies in cerebral cortex membranes indicated that this ligand bound to a single site with apparent high affinity (K D = 4.6 ± 1.6 and 3.1 ± 0.37 nM, Bmax = 13.7 ± 1.6 and 21.8 ± 2.2 fmol/mg protein in rat and guinea pig membranes, respectively). However, in competition studies with a group of neurokinins and related peptides two different rank orders of affinities were obtained, as follows: NKB > [MePhe 7]-NKB ≥ Arg 0-NKB ≥ Senktide ⪢ NKA > SP, in rat membranes, and [MePhe 7]NKB > Senktide = NKB > Arg 0-NKB ⪢ SP > NKA, in guinea pig membranes.