beta-endorphin is a potent analgesic agent.

Abstract
.beta.-Endorphin, an opiate-like peptide, has potent antinociceptive properties when it is administered directly into the brain and assayed in the tail-flick, hot-plate and writhing tests in mice and in the wet shake test in rats. On a molar basis, .beta.-endorphin is 18-33 times more potent than morphine, and its actions are blocked by the specific opiate antagonist, naloxone hydrochloride. The activity of .beta.-endorphin in vivo is also compared to other peptides that show opiate-like activity in assays in vitro.