Synthesis of Peptides Related to Substance P and Their Activities as Agonists and Antagonists.

Abstract

Analogs (7) of substance P (SP) were synthesized by a solid-phase technique. Tests for agonistic and antagonistic activities were performed on the isolated guinea pig ileum. [D-Phe9]-SP had very low agonistic activity, but no significant antagonistic activity. [Ile7, Ile8]-SP had low activity but [Ile8]-SP was almost twice as active as SP. Heptapeptide analogs of [Ile8]-SP having a basic L or D-amino acid at the N-terminal (Lys or D-Arg) were almost as active as SP.