Somatostatin, Substance P and [Lys]-Vasopressin Interfere with the Binding of [³H][D-Ala², Met⁵]Enkephalinamide to Rat Brain Membranes

Abstract

Somatostatin and substance P (10^-6-3×10^-5 M) inhibited dosedependently the specific binding of [³H] [D-Ala², Met⁵]enkephalinamide ([³H]-DALAMID) to rat brain membranes, by decreasing the number of binding sites. [Lys]-Vasopressin also inhibited the binding, by affecting both the number of binding sites and the affinity of receptors to [³H]DALAMID. The results indicate that somatostatin and substance P may interfere with the endorphin system by an apparently competitive manner.