Prenatal Opioid Exposure Enhances Responsiveness to Future Drug Reward and Alters Sensitivity to Pain: A Review of Preclinical Models and Contributing Mechanisms.

The opioid crisis has resulted in an unprecedented number of neonates born with prenatal opioid exposure (POE); however, the long-term effects of POE on offspring behavior and neurodevelopment remain relatively unknown. The advantages and disadvantages of the various preclinical POE models developed over the last several decades are discussed in the context of clinical and translational relevance. Although considerable and important variability exists among preclinical models of POE, the examination of these preclinical models has revealed that opioid exposure during the prenatal period contributes to maladaptive behavioral development as offspring mature including an altered responsiveness to rewarding drugs and increased pain response. The present review summarizes key findings demonstrating the impact of POE on offspring drug self-administration, drug consumption, the reinforcing properties of drugs, drug tolerance, and other reward-related behaviors such as hypersensitivity to pain. Potential underlying molecular mechanisms which may contribute this enhanced addictive phenotype in POE offspring are further discussed with special attention given to key brain regions associated with reward including the striatum, prefrontal cortex, ventral tegmental area, hippocampus, and amygdala. Improvements in preclinical models and further areas of study are also identified which may advance the translational value of findings and help address the growing problem of POE in clinical populations. Significance Statement As the number of the infants born following prenatal opioid exposure continues to increase, there is a greater need to employ preclinical models to study the potential consequences of POE and brain and behavioral development. A large body of evidence indicates POE is associated with alterations in reward-related behavior and molecular adaptations in reward neurocircuitry. This review seeks to: (1) provide an overview of the various types of preclinical models developed over the last few decades; (2) review the numerous behavioral studies examining drug-reward related behavior in offspring with POE; and (3) discuss potential contributing molecular mechanisms to this enhanced reward phenotype observed in POE offspring.