A substance in
amniotic fluid and
placenta (POEF for Placental Opioid-Enhancing Factor) has been shown to enhance opiate- or opioid-mediated
analgesia in rats. Recent studies have only touched on the
generalizability of the phenomenon. The present studies further tested the
generalizability of the POEF effect: they examined sex specificity of the mechanism; whether POEF activity exists in
afterbirth material of species other than the rat; whether POEF activity exists in tissue other than
afterbirth material; whether POEF activity could be demonstrated after injection rather than
ingestion of
afterbirth material; and whether POEF enhances all opioid-mediated phenomena. We found that (a) POEF is effective in male rats as well as in female rats; (b) POEF activity exists in human and dolphin
afterbirth material; (c)
ingestion of pregnant-rat
liver does not produce enhancement of opioid-mediated
analgesia; (d) POEF does not seem to be effective when
amniotic fluid is injected either IP or SC; and (e) POEF does not modify morphine-induced
hyperthermia.
