Chronic prenatal cocaine treatment down-regulates mu-opioid receptor mRNA expression in the brain of fetal Rhesus Macaque

Ribonuclease protection assays (RPA) were performed to quantify mu-opioid r eceptor mRNA expression in specific brain regions of day 70 Rhesus Macaque fetuses that were exposed to cocaine (3 mg/kg) or saline from days 22-70 of gestation. The content of mu-receptor mRNA was high in the diencephalon an d moderate in the mesencephalon. In contrast, mu-receptor mRNA was lightly expressed in areas such as the frontal cortex, striatum and the temporal lo be. The content of mu-opioid receptor mRNA was significantly higher in the diencephalon than in other brain regions (P < 0.001; n = 4). Cocaine exposu re significantly decreased the expression of mu-receptor mRNA in the fetal diencephalon (P < 0.05; n = 4 in each group). Our data would indicate that prolonged gestational cocaine exposure causes mu-opioid receptor mRNA down- regulation in specific brain regions of the fetus. (C) 1999 Published by El sevier Science Ireland Ltd. All rights reserved.