264 Challenges of Sex Differences Research in Neuroscience: The role of central estradiol in heroin extinction memory retention in male and female rodents

Abstract

OBJECTIVES/GOALS: Misprescription of opioids has led to an epidemic of opioid use disorder (OUD). Females, among other differences, have increased susceptibility to the addictive properties of opioids. Yet, the exclusion of female subjects from many foundational studies on reward processing had hindered our ability to fully understand these disparities. METHODS/STUDY POPULATION: Estradiol (E2), a neuronal sex steroid, may play a role in sex differences in OUD. In this study, we used fadrozole, an aromatase inhibitor, to characterize the role of centrally produced E2 in heroin cue extinction memory retention (EMR, “remembering to forget”). Male and female rats self-administered heroin in a long-access paradigm (6hr/day) for 8 days, where a light/tone cue was co-presented with each infusion of heroin. This was followed by 1 day of cued extinction (6hr; light/tone but no heroin). Just prior to this session, fadrozole was infused into the basolateral amygdala (BLA) through implanted cannulas. The next day, subjects were given a cued EMR test (1hr; light/tone but no heroin) following another infusion of fadrozole. RESULTS/ANTICIPATED RESULTS: Females took more heroin than males (mg/kg) despite having similar active nose poke responding during acquisition. Regardless of aromatase inhibition, females had higher active nose pokes during the first hour of cued extinction relative to males. Both males and females treated with fadrozole in the BLA prior to cued extinction had impaired EMR on test, evidenced by increased active nose pokes and lower extinction indices relative to vehicle controls. Upon examination of the brains, we expect that aromatase inhibition will have impaired neuronal plasticity, as evidenced by decreases in numerous measures of plasticity. Furthermore, we expect to find sex differential expression of estrogen receptor (ER) subtypes throughout the BLA, suggesting a convergent sex effect of E2 on heroin EMR. DISCUSSION/SIGNIFICANCE: This study is the first to examine a behavioral role for central E2 in the BLA. Future studies will examine specific roles for ER subtypes on this behavior and synaptic plasticity. A better understanding of sex specific E2 signaling will promote further research on sex differences and allowing us to better address disparities in disorders like OUD.