text: The involvement of EP1 and EP2 receptors is indicated by studies with the << EP1 >> selective agonist [[ 17-phenyl trinor PGE2 ]], and the EP2 selective agonist butaprost (which stimulate), as well as by studies with the antagonists SC-51089 (EP1 specific) and AH 6809 (EP1 and EP2 specific).