Mice exposed to the opioid oxycodone before birth experience permanent changes in behavior and gene expression. The new research published in eNeuro highlights a need to develop safer types of painkillers for pregnant women.

Opioids like oxycodone are prescribed to pregnant women to treat pain, but the drugs may affect the fetus, too. Opioids can pass through the placenta, binding to receptors in the fetal brain, which can lead to opioid withdrawal in newborn babies. The long-term consequences of prenatal opioid exposure haven't been fully studied, however.

To explore this, the authors administered oxycodone to female mice every day for the two weeks prior to and throughout the duration of their pregnancy. The team administered a range of behavioral tests on the offspring during weaning and later in adulthood.

The offspring exposed to oxycodone during gestation showed signs of impaired social behaviors and communication. They were also larger and less active than the control mice.

The research team examined the gene expression of opioid receptors in the offspring. In the hippocampus, a region involved in learning and memory, one type of receptor increased in male mice while a different receptor decreased in female mice. These results reveal prenatal opioid exposure can have lifelong effects on offspring.

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