The "endorphin story": a subjective account

The contribution of the researchers of IDR to some early discoveries on endorphins is recounted. Exact determination of the amino acid sequence of beta-lipotropin, discovery of the analgesic action of beta-endorphin in rats, demonstration of the partial cross-tolerance between morphine and beta-endorphin, description of the elevation of the pain threshold upon inhibition of the enzymatic breakdown of endogenous opioids by bacitracin, demonstration of inhibition of opiate tolerance and dependence by alpha-MSH and Met-enkephalin, development of the second strongest enkephalin analogue, D-Met2,Pro5-enkephalinamide, recognition of some factors conferring analgesic activity to synthetic enkephalin analogues, etc. prove that IDR has played an active role in the early history of endorphin research.