[Discovery of the analgesic action of beta-endorphin: a subjective account].

The contribution of the research workers of the Institute for Drug Research to some early discoveries in the field of endorphins is reviewed. The author takes pride in the fact the analgesic action of beta-endorphin was described in his laboratory concurrently with an American and a British group, respectively. The other main findings of his laboratory include demonstration of the cross-tolerance between beta-endorphin and morphine, description of the elevation of the pain threshold upon inhibition of the breakdown endogenous opioids by intracerebroventricular administration of bacitracin, attenuation of morphine tolerance by alpha-MSH and Met-enkephalin, pharmacological development and clinical examination of a highly potent enkephalin analogue, (D-Met2,Pro5)-enkephalinamide, coded as GYKI 14,238.