Sialogogic Effects on Rat Submandibular Gland of Analogs of the C-Terminal Hexapeptide of Substance P

Abstract

The sialogogic response of submandibular glands to analogs of the C-terminal hexapeptide of substance P with various amino acids at the N-terminus was investigated in urethane-anesthetized rats. The rank order of potencies was as follows: SP > (pGlu⁶)SP_6-11 >> (Dab⁶)SP_6-11 > (Orn⁶)SP_6-11 > (Gln⁶)SP_6-11 > (Lys⁶)SP_6-11 >> (Ala⁶)SP_6-11. These results suggest that the sialogogic activity of the analogs of the C-terminal hexapeptide is influenced by the steric effects of the N-terminal amino acid, and the nature of its side chain is of particular importance.