Charday (Long) Waters
Education: Bachelor of Science in psychology (December 2018)
McNair Project: Relapse to Fentanyl Seeking after Choice-based Voluntary Abstinence (2018). Completed at the National Institute on Drug Abuse in Baltimore, Maryland.
Development Mentor: Charles Pickens, Ph.D.
Project Mentors: Yavin Shaham, Ph.D., and David Reiner, Ph.D. (National Institute on Drug Abuse, Baltimore, MD)
High relapse rates are a core feature of addiction, but few preclinical animal models of drug relapse incorporate a critical component of human addiction and relapse: self-imposed abstinence. The Shaham lab developed a rat model of choice-based voluntary abstinence to more closely mimic the voluntary component of abstinence in humans. Sprague-Dawley rats (n=14 male, 14 female) were first trained to self-administer palatable food pellets for 6 days, followed by 14 days of intravenous fentanyl self-administration (2.5 μg/kg/infusion) for 12 days. During the voluntary abstinence phase, rats could lever press for palatable food or fentanyl in mutually exclusive choice trials. On day 1 and day 14 of abstinence, rats were tested for relapse to fentanyl seeking in the absence of the drug. Subsequently, rats were perfused, and brains were collected for Fos immunohistochemistry to identify brain regions associated with increased neural activity during fentanyl relapse. Results show that there are no sex differences in intravenous fentanyl self-administration, no increases in relapse responding from day 1 to day 14 (incubation of drug craving), and no differences in voluntary abstinence. Relapse to fentanyl seeking after voluntary abstinence is associated with increased Fos expression in including the Orbitofrontal Cortex (OFC) and Insula. The causal role of the OFC and Insula in fentanyl relapse is currently being tested using reversible inactivation with GABA receptor agonists muscimol+baclofen. Collectively, these results extend our previous findings that choice-based voluntary abstinence prevents incubation of heroin craving and future experiments will investigate the role of pain in fentanyl relapse.