Opioid use disorder (OUD) is a chronic disorder characterized by the ability of drug-associated cues (triggers) to persistently motivate drug-seeking behaviors, despite negative consequences. When drugs are associated with cues, a strong conditioned memory is formed between the drug and the cues. Normally, once these cues no longer predict a drug reward, this conditioned memory would be overpowered by an extinction memory. Extinction memory recall (EMR) describes the ability to behaviorally express this extinction memory. EMR deficits may underly the pathological drug seeking (relapse) seen in those with OUD. Importantly, a brain region involved in each step of this process (conditioning, extinction and EMR) is the basolateral amygdala (BLA). OUD is also characterized by distinct sex differences, with females being particularly susceptible to the rewarding effects of opioids and more reactive to opioid-associated cues. Unfortunately, the lack of females in many prior research studies on OUD has impaired our ability to describe the mechanisms behind, and thereby address, these disparities. To resolve this knowledge gap, we conducted preliminary studies to investigate the role of estradiol (E2) signaling in the BLA on heroin EMR in male and females rodents. In our first study, we found that blocking E2 synthesis in the BLA during cued extinction training impairs EMR in both sexes. On follow-up, we found that antagonizing estrogen receptor (ER) subtypes in the BLA led to sex-specific impacts on heroin EMR. Briefly, females who received an ERβ antagonist had a profound EMR deficit relative to all other groups tested. In agreement, ERβ agonism enhanced EMR in females only. The goal of this proposal is to evaluate the sex- specific impacts of ERβ signaling in the BLA on heroin EMR. We hypothesize that modulation of ERβ signaling in the BLA during extinction will alter EMR in females by changing neuronal function and plasticity-associated mRNA expression, an effect driven by sex-specific ERβ expression in the BLA. We will evaluate this hypothesis across 2 Aims. We propose to use pharmacologic and genetic approaches in males and females to identify alterations in BLA activity and signaling following negative (Aim 1) or positive (Aim 2) modulation of ERβ during cued extinction. Upon analysis, we expect that negative ERβ modulation by antagonist or shRNA (Aim 1) will impair heroin EMR, decrease ERβ+ neuronal activity, and decrease plasticity-associated mRNA expression in females. Contrastingly, positive modulation of ERβ by agonist or overexpression (Aim 2) will have opposite impacts on these measures in females. The proposed studies may better describe sex differences underlying heroin reward processing and OUD, allowing for more guided, sex- specific interventions to successfully prevent and treat this disorder. This fellowship will support my training under the mentorship of Drs. Carmela Reichel and Christopher Cowan. As outlined in this proposal, I wil...