Bifunctional pharmacophores. Biological activities of the peptide analog containing both casomorphine-like and substance P antagonist-like active elements.

SP-antagonistic properties of a newly synthesized peptide Tyr-Pro-D-Phe-Phe-D-Phe-D-Trp-MetNH2 (AWL-60) were investigated both in vitro and in vivo. In vitro AWL-60 effectively antagonized the action of SP-agonist (SP6-11); however, this antagonism was non-competitive. Antagonistic properties of AWL-60 were also observed in vivo: in doses as low as 0.1 nmol/kg iv AWL-60 markedly attenuated the fall in blood pressure produced by [less than Glu]6SP6-11. Since AWL-60 exerts weak opioid agonistic properties (as a casomorphine analog) the possible involvement of an opioid agonistic component in their SP inhibitory action is considered.