Postnatal environment differentially modulates neurodevelopmental outcomes following voluntary prenatal oxycodone exposure in rats.

As prenatal opioid exposure becomes increasingly prevalent, understanding which neurodevelopmental effects are amenable to postnatal intervention has become a critical question. Clinically, prenatal exposure and maternal factors that affect offspring development often co-occur, making it difficult to determine which developmental outcomes are directly attributable to drug effects versus postnatal environmental influences. Preclinical models can be useful in disentangling these interacting factors. Using a rat model of voluntary maternal Oxycodone (Oxy) self-administration, we examined whether postnatal rearing environment could ameliorate neonatal opioid withdrawal syndrome (NOWS)-like symptoms. Cross-fostering separated prenatal drug effects from postnatal rearing and revealed differential sensitivity to environmental modification. Altered ultrasonic vocalizations were rescued when Oxy-exposed offspring were reared by drug-naïve dams, while increased motor activity persisted regardless of rearing condition. Oxy-exposed offspring reared by Oxy-exposed dams showed a distinct developmental trajectory characterized by increased vocal power and reduced frequency variability. These early alterations persisted across the postnatal period. Unexpectedly, maternal opioid intake levels during pregnancy did not predict NOWS-like symptom severity. However, early vocalization patterns did show group-specific predictive relationships with adult markers (plasma corticosterone and nucleus accumbens MeCP2 expression), suggesting potential continuity between early behavioral alterations and later physiological changes. The functional significance of these relationships requires further investigation. Overall, some, but not all, developmental effects of prenatal opioid exposure could be ameliorated by the postnatal rearing environment. These findings suggest that early behavioral profiles may help identify offspring at greatest risk for persistent developmental alterations, highlighting the potential value of early assessment and postnatal intervention.