Enkephalin analogues eliciting analgesia after intravenous injection

Abstract Extensive study of structure-activity relations in enkephalin-like peptides has led to analogues which are up to 70 times more potent than Leu-enkephalin in vitro in the electrically-stimulated guinea pig ileum preparation, and which are analgesic in the mouse hot-plate test at doses as low as 5mg/kg following intravenous administration.