Importance of opiate receptor ligands in regulating lymphocyte proliferative activity

Effects of morphine (10(-12)-10(-6) M), metenkephalin (10(-12)-10(-6) M), beta-endorphin (10(-12)-10(-6) M), dalargin--synthetic analogue of leu-enkephalin (10(-12)-10(-7) M) and naloxone (10(-8)-10(-6) M) on lymphocytes of the human peripheral blood stimulated by polyclonal mitogens were studied. It was shown that morphine (10(-8)-10(-6) M) and dalargin (10(-12)-10(-7) M) inhibited the lymphocyte proliferative activity induced by optimal doses of phytohemagglutinin; effects of morphine and dalargin were blocked by naloxone. It was also found that beta-endorphin (10(-11)-10(9) M) inhibited the proliferative activity of lymphocytes stimulated by pokeweed mitogen; naloxone failed to block beta-endorphin effect.