title: Oxycodone physical dependence and its oral self-administration in C57BL/6J mice.
abstract: Abuse of prescription opioids, such as oxycodone, has markedly increased in recent decades. While oxycodone's antinociceptive effects have been detailed in several preclinical reports, surprisingly few preclinical reports have elaborated its abuse-related effects. This is particularly surprising given that oxycodone has been in clinical use since 1917. In a novel oral operant self-administration procedure, C57BL/6J mice were trained to self-administer water before introducing increasing concentrations of oxycodone (0.056-1.0mg/ml) under post-prandial conditions during daily, 3-h test sessions. As the concentration of oxycodone increased, the numbers of deliveries first increased, then decreased in an inverted U-shape fashion characteristic of the patterns of other drugs self-administered during limited access conditions. After post-prandial conditions were removed, self-administration at the highest concentration was maintained suggesting oral oxycodone served as a positive reinforcer. In other mice, using a novel regimen of physical dependence, mice were administered increasing doses of oxycodone (9.0-33.0mg/kg, s.c.) over 9 days, challenged with naloxone (0.1-10.0mg/kg, s.c.), and then observed for 30min. Naloxone dose-dependently increased the observed number of somatic signs of withdrawal, suggesting physical dependence of oxycodone was induced under this regimen. This is the first report demonstrating induction of oral operant self-administration of oxycodone and dose-dependent precipitations of oxycodone withdrawal in C57BL/6J mice. The use of oral operant self-administration as well as the novel physical dependence regimen provides useful approaches to further examine the abuse- and dependence-related effects of this highly abused prescription opioid.
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, 410 N. 12th Street, Richmond, VA 23298, USA.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Enga
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, 410 N. 12th Street, Richmond, VA 23298, USA.
authors.forename: Asti
authors.initials: A
authors.lastname: Jackson
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, 410 N. 12th Street, Richmond, VA 23298, USA; Institute for Drug and Alcohol Studies, Virginia Commonwealth University, P.O. Box 980310, Richmond, VA 23298-0310, USA.
authors.forename: M Imad
authors.initials: MI
authors.lastname: Damaj
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, 410 N. 12th Street, Richmond, VA 23298, USA; Institute for Drug and Alcohol Studies, Virginia Commonwealth University, P.O. Box 980310, Richmond, VA 23298-0310, USA; Center for Biomarker Research and Personalized Medicine, School of Pharmacy, Virginia Commonwealth University, 1112 East Clay Street, Richmond, VA 23298, USA. Electronic address: patrick.beardsley@vcuhealth.org.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Beardsley
mesh_terms: D000284:Administration, Oral; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009021:Morphine Dependence / Q000209:etiology* / Q000523:psychology / Q000628:therapy; D010098:Oxycodone / Q000008:administration & dosage* / Q000494:pharmacology*; D019518:Postprandial Period / Q000187:drug effects; D012054:Reinforcement, Psychology; D012646:Self Administration
chemical_list: D010098:Oxycodone
keywords: Dependence; Mouse; Oral self-administration; Oxycodone; Prescription opioid