%A Jean M. DiPirro %A Alexis C. Thompson %A Dr. Mark B. Kristal %J Brain Research Bulletin %T Amniotic-Fluid Ingestion Enhances the Central Analgesic Effect of Morphine %X Amniotic fluid and placenta contain a substance (POEF) that when ingested enhances opioid-mediated analgesia produced by several agents (morphine injection, vaginal/cervical stimulation, late pregnancy, footshock), but not that produced by aspirin injection. The present series of experiments employed quaternary naltrexone, an opioid antagonist that does not readily cross the blood-brain barrier, in conjunction with either peripheral or central administration of morphine, to determine whether amniotic-fluid ingestion (and therefore POEF ingestion) enhances opioid-mediated analgesia by affecting the central and/or peripheral actions of morphine. The results suggest that POEF affects only the central analgesic effects of morphine. %N 6 %K POEF, analgesia, pain, rats, morphine, opioids, placenta, quaternary naltrexone, amniotic fluid, placentophagia, naltrexone methobromide %P 851-855 %V 26 %D 1991 %I Pergamon Press %L cogprints6211