Effects of methadone use during pregnancy on human placental opioid receptors.

Human placenta was used to investigate the effects of chronic methadone use during pregnancy on villus tissue opioid receptors. Patients included in this investigation received 35-60 mg methadone per day. Methadone-exposed placenta villus tissue had no detectable opioid receptor binding sites measured by tritiated opioid agonists. In vitro release of acetylcholine and hCG from trophoblast tissue of methadone-exposed placentas was not modulated by opioids. Absence of opioid receptor binding sites and their two mediated responses in trophoblast tissue of placentas obtained from patients with documented chronic methadone use during pregnancy indicate that the receptors were down regulated or desensitized.