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Behavioral flexibility and gut microbiome as potential predictors of oral oxycodone self-administration

ABSTRACT: Prescription opioids such as oxycodone have been widely used in the United States and have contributed to the ongoing opioid epidemic. While many individuals limit use to prescribed contexts, a subset transitions to misuse and, in some cases, to illicit opioid use. Identifying behavioral and biological factors that predict this vulnerability is critical for improving prevention and intervention strategies. Here, we investigated whether individual differences in behavioral flexibility and gut microbiome composition are associated with future oxycodone intake using a translationally relevant model of oral oxycodone self-administration in male and female Long-Evans rats. We established a model in which distinct intake phenotypes emerged, characterized by animals with high versus low oxycodone consumption. Behavioral flexibility, assessed using a contingency degradation task, was associated with oxycodone intake, identifying it as a potential behavioral biomarker of vulnerability. In parallel, oral oxycodone exposure altered gut microbiome composition, and microbiome features were associated with both behavioral flexibility and drug-taking behavior. These findings support a framework in which individual differences in opioid intake arise from the interaction of pre-existing behavioral traits and biological states, including gut microbiome composition which provides a foundation for identifying predictive biomarkers and developing individualized strategies to mitigate risk for opioid misuse.

ORGANISM(S): feces metagenome

PROVIDER: GSE326997 | GEO | 2026/04/03

REPOSITORIES: GEO

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Project description:Opioids analgesics are frequently prescribed in the United States and worldwide. However, serious side effects such as addiction, immunosuppression and gastrointestinal symptoms limit their use. It has been recently demonstrated that morphine treatment results in significant disruption in gut barrier function leading to increased translocation of gut commensal bacteria. Further study indicated distinct alterations in the gut microbiome and metabolome following morphine treatment, contributing to the negative consequences associated with opioid use. However, it is unclear how opioids modulate gut homeostasis in the context of a hospital acquired bacterial infection. In the current study, a mouse model of C. rodentium infection was used to investigate the role of morphine in the modulation of gut homeostasis in the context of a hospital acquired bacterial infection. Citrobacter rodentium is a natural mouse pathogen that models intestinal infection by enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) and causes attaching and effacing lesions and colonic hyperplasia. Morphine treatment resulted in 1) the promotion of C. rodentium systemic dissemination, 2) increase in virulence factors expression with C. rodentium colonization in intestinal contents, 3) altered gut microbiome, 4) damaged integrity of gut epithelial barrier function, 5) inhibition of C. rodentium-induced increase in goblet cells, and 6) dysregulated IL-17A immune response. This is the first study to demonstrate that morphine promotes pathogen dissemination in the context of intestinal C. rodentium infection, indicating morphine modulates virulence factor-mediated adhesion of pathogenic bacteria and induces disruption of mucosal host defense during C. rodentium intestinal infection in mice. This study demonstrates and further validates a positive correlation between opioid drug use/abuse and increased risk of infections, suggesting over-prescription of opioids may increase the risk in the emergence of pathogenic strains and should be used cautiously. Therapeutics directed at maintaining gut homeostasis during opioid use may reduce the comorbidities associated with opioid use for pain management.

Project description:The number of individuals diagnosed with opioid use disorder (OUD) has risen steeply because of the increased prescribing of opioid drugs like oxycodone for chronic pain relief. OUD is characterized by loss of control of drug taking, continued drug use in the presence of adverse consequences, and repeated relapses to drug taking. Repeated exposure to oxycodone self-administration can lead to addiction in certain rats while others remain unaffected. Understanding the molecular mechanisms between these two groups holds promise for developing strategies to combat addiction. To identify signaling pathways associated with oxycodone addition, this study used male Sprague-Dawley rats to self-administer oxycodone for 20 days according to short-(ShA, 3 h) and long-access (LgA, 9 h) paradigms. Animals were euthanized after 2 hours of self-administration cessation and their dorsal striata were used for RNA sequencing analysis. LgA rats escalated their oxycodone intake and developed into 2 phenotypes, named long-access high (LgA-H, addicted) and long-access lower (LgA-L, non-addicted) rats, based on the level of escalation and drug taken during the self-administration experiment. RNA sequencing revealed many differentially expressed genes in the oxycodone-addicted rats in comparison to other groups. DAVID analysis indicated that some of these genes were involved in potassium transport, ATP binding, and regulation of synaptic processes. Ingenuity pathway analysis (IPA) revealed previous involvement of some genes in OUD and cognitive processes. RNA sequencing and RT-PCR analysis of dorsal striatum samples unveiled a significant upregulation of potassium channel genes Kcnma1, Kcnk9, Kcnq1, Kcnd3, and Kcng3 in LgA-H rats, which was corelated with oxycodone intake. We also identified increased expression for Cldn3, Serping1, and Serpinh1 in ShA rats. Taken together, these observations identified potassium channels as potential targets for the treatment of oxycodone use disorder.

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Behavioral flexibility and gut microbiome as potential predictors of oral oxycodone self-administration

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