Caleb I Hodges, Eamonn P Duffy, Jonathan O Ward, Luanne H Hale, Cove C Andrews, Laura M Saba, Marissa A Ehringer, Ryan K Bachtell
Despite much less total cocaine consumption IntA resulted in incubation of craving and enhancements in NAc CP-AMPAR plasticity similar to LgA. This adds to a growing literature demonstrating that the intermittency of cocaine consumption can produce robust neurobehavioral plasticity comparable to LgA, in the absence of high levels of cocaine consumption.
INTRODUCTION: Opioid Use Disorder (OUD) remains a prominent threat to global health. Genetic background influences the susceptibility of developing OUD, although specific genetic factors remain elusive. Rodent models that differ in susceptibility to escalation and dysregulation of opioid use are valuable tools to facilitate discovery of genetic pathways.
MATERIALS AND METHODS: Phenotypes associated with the development of OUD were compared in seven classic inbred rat strains (M520/N, WKY/NCrl, F344/NCrl, F344/Stm, LEW/Crl, LEW/SSNHsd, LE/Stm) from the Hybrid Rat Diversity Panel (HRDP). A two-phase self-administration paradigm was utilized to assess characteristics of the acquisition of oxycodone self-administration during daily 2-h sessions, and the escalation of oxycodone use during daily 12-h sessions.
RESULTS: Genetic background influenced the acquisition of oxycodone self-administration as indicated by differences in the initiation of responding for oxycodone during each session and different amounts of oxycodone intake. We observed that escalation of oxycodone intake between-sessions was strain dependent, and the within-session distribution of oxycodone intake was strongly influenced by strain. The M520/N strain engaged in a unique pattern of intake, characterized by rapid initiation of oxycodone responding during the acquisition phase and a significant burst-like responding during escalation. Strain-dependent sex differences were also observed in several acquisition and escalation metrics. Of interest, rapid burst responding was more prevalent in females of the M520/N strain compared to males.
DISCUSSION: Together, these data indicate that genetic background influences not only overall oxycodone intake, but specific within- and between-session metrics that capture patterns of consumption across the substance use trajectory.