Strips of rabbit mesenteric arteries precontracted with phenylephrine relaxed when exposed to des-Arg9-bradykinin (BK), a typical B1 receptor agonist. We showed that the ability of des-Arg9-BK to relax this preparation was acquired during in vitro incubation and was abolished by cycloheximide treatment. In this preparation intimal damage reduced but did not abolish the relaxant effect of des-Arg9-BK, and indomethacin uncovered a contractile effect of des-Arg9-BK also acquired during the in vitro incubation.