RT Journal Article SR Electronic T1 Biological Activity of Substance P Methyl Ester JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 457 OP 459 VO 20 IS 3 A1 MARGARET A. CASCIERI A1 MARVIN M. GOLDENBERG A1 TEHMING LIANG YR 1981 UL http://molpharm.aspetjournals.org/content/20/3/457.abstract AB The COOH-terminal amide of substance P was replaced with a methyl ester, and the potency of this substance P methyl ester was compared with that of substance P and substance P free acid in stimulating salivation in rats and in stimulating guinea pig ileum contraction in vitro. Compared with substance P, substance P methyl ester was found to be 30% as potent in stimulating salivation and equipotent in ileum contraction. Substance P free acid was only 0.1% and 0.9% as potent as substance P in stimulating salivation and ileum contraction, respectively. The results suggest that the hydrophobicity of the COOH-terminal portion of substance P may be important for the molecule in its interaction with the substance P receptor. ACKNOWLEDGMENTS We are grateful to E. M. Subers for assistance in the guinea pig ileum assay, to Drs. E. H. Cordes and D. F. Veber for their review of the manuscript, and to Ms. Madeline Spencer for typing the manuscript.