Dissertations, Theses, and Capstone Projects

Date of Degree

6-2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Psychology

Advisor

Peter Serrano

Committee Members

Richard Bodnar

Robert Ranaldi

Regina Sullivan

Gordon Barr

Subject Categories

Biological Psychology | Psychology

Keywords

prenatal opioid exposure, play behavior, development

Abstract

Prenatal opioid exposure has increased as a consequence of both increased Opioid Use Disorder (OUD) and prescription use for treatment of pain and OUD. However, human studies on prenatal opioid exposure are complicated by several confounding variables and thus, use of an animal model can lessen these confounds. Illicit use of opioids produces fluctuating blood levels whereas prescribed use of opioids results in stabilized blood levels of opioids. Our first study sought to determine if different methods of opioid administration, resulting in differing blood levels of opioids, would impact social play, a developmentally important behavior that is modulated by the endogenous opioid system. Once daily injection of morphine provided intermittent opioid treatment and morphine pellet implantation provided continuous administration in pregnant rats. Play was measured in three age groups: PD 25, PD 35, and PD 45. The number of pups, as well as the amount of play, significantly increased with age, especially from PD25 and PD35. At PD 25, the number of pups that played was decreased in pups that were exposed continuously (pre and postnatally), but this effect was not seen for the number of occurrences of the play behaviors. There were also an increase in non-play behaviors by age, from PD25 to PD 35 and PD25 to PD45 but minimal effects of treatment on occurrences or number of non-play behaviors. The second study focused on continuous pre and postnatal exposure, due to the prolonged duration of the morphine pellet exposure. Pups were cross-fostered such that pups that were prenatally exposed to a drug-naïve dam were raised by a drug-exposed dam and vice versa. Two groups of pups implanted with pellets or sham implants were not cross-fostered. The results show that although there was no significant effect of treatment condition on the amount of play, the number of pups that played was significantly lower in the pups that received both pre and postnatal opioid exposure. There were no significant differences in non-play behavior in the second study. The results of these studies suggest that both pre and postnatal opioid exposure are more impactful than prenatal or postnatal exposure alone.

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