the quality of analgesia in relation to the plasma concentration of betaendorphin during neuroleptanalgesia and epidural analgesia in 66 patients who had to undergo radical abdominal hysterectomy because of cancer of the cervix uteri the plasma concentrations of betaendorphin were observed intra and postoperatively two anaesthetic techniques were used neuroleptanalgesia and thoracolumbar epidural analgesia with sedation and controlled inhalation of a mixture of oxygen and nitrous oxide while the higher dosage of analgesics administered intraoperatively resulted in markedly lower plasma concentrations of betaendorphin there was no such effect in the postoperative phase patients with epidural analgesia who were absolutely painless postoperatively had during that stage higher concentrations of betaendorphin in the plasma than those patients who had been given neuroleptanalgesia they had received no analgetic treatment during the postoperative observation period these differences are attributed to an increased adaptability of patients subsequent to neuroleptanalgesia the neuronal block can result in a decrease in functional activity of the suprarenal medulla and impair adaptability the stressinduced opioid analgesia can be suppressed by circulating enkephalin from the suprarenal medulla