Impaired Expression of Mu- and Kappa-Opioid Receptor mRNA in the Midbrain of Rats with Prenatal Alcohol Intoxication

Disruption of normal epigenetic reprogramming during the prenatal period under the influence of exogenous factors affects fetus development and adult phenotype formation. The mechanisms through which determinants, such as maternal alcohol intake, contribute to the formation of an alcohol-vulnerable phenotype later in life still remain unclear. In this paper, we suggest that alteration in the reinforcing properties of ethanol in prenatally alcohol-exposed subjects may be associated with transcriptional dysregulation of the brain opioid receptor genes. We compared voluntary alcohol intake and levels of mRNA coding for μ- (MOP) and κ-opioid (KOP) receptors in the mesolimbic areas of adult male offspring of the female Wistar rats having received 10% ethanol as the only source of liquid throughout pregnancy or water (control). We found that prenatally alcohol exposed rats had higher alcohol preference on PND60 (free-choice paradigm) and lower mRNA expression for both MOP and KOP in the midbrain compared to the control. This suggests a potential link between prenatal alcohol, dysfunction of the brain opiate system and adult vulnerability for alcohol use disorder.