beta-endorphin-(1-27) is an antagonist of beta-endorphin analgesia.

Abstract
.beta.h-Endorphin-(1-27), a naturally occurring fragment of human .beta.-endorphin (.beta.h-endorphin), diminishes the analgesic effect of .beta.h-endorphin when coinjected intracerebroventricularly into mice. A parallel shift in the dose-response curve of .beta.h-endorphin in the presence of .beta.h-endorphin-(1-27) suggests competition at the same site. The potency of .beta.h-endorphin-(1-27) in antagonizing analgesia is > 4 times greater than that of the opiate antagonist naloxone.