title: Predicting addictive vulnerability: individual differences in initial responding to a drug's pharmacological effects.
abstract: Considerable data suggest that individuals who appear minimally disrupted during an initial drug administration have elevated risk for abusing the drug later. A better understanding of this association could lead to more effective strategies for preventing and treating drug addiction. To investigate this phenomenon using a rigorous experimental model, we first administered the abused inhalant nitrous oxide (N2O) to rats in a total calorimetry and temperature system to identify groups that were sensitive or insensitive to the drug's hypothermic effect. We then enrolled the two groups in a novel N2O self-administration paradigm. The initially insensitive rats self-administered significantly more N2O than sensitive rats, an important step in the transition to addiction. Continuous non-invasive measurement of core temperature and its underlying determinants during screening revealed that both groups had similarly increased heat loss during initial N2O administration, but that insensitive rats generated more heat and thereby remained relatively normothermic. Calorimetry testing conducted after self-administration revealed that whereas N2O's effect on heat loss persisted comparably for both groups, initially insensitive rats actually over-responded by generating excess heat and becoming hyperthermic. Thus, rats with the greatest initial heat-producing compensatory response(s) appeared initially insensitive to N2O-induced hypothermia, subsequently self-administered more N2O, and developed hyperthermic overcompensation during N2O inhalation, consistent with increased abuse potential and an allostatic model of addictive vulnerability.
authors.affiliation: Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America.
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Ramsay
authors.affiliation: Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America.
authors.forename: Salwa
authors.initials: S
authors.lastname: Al-Noori
authors.affiliation: Department of Biostatistics, University of Washington, Seattle, WA, United States of America.
authors.forename: Jason
authors.initials: J
authors.lastname: Shao
authors.affiliation: Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America; Department of Biostatistics, University of Washington, Seattle, WA, United States of America.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Leroux
authors.affiliation: Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, United States of America.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Woods
authors.affiliation: Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Kaiyala
mesh_terms: D000280:Administration, Inhalation; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000009:adverse effects*; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D002151:Calorimetry; D004361:Drug Tolerance; D007035:Hypothermia / Q000139:chemically induced*; D007206:Individuality; D008297:Male; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000009:adverse effects*; D051381:Rats; D020318:Rats, Long-Evans; D019966:Substance-Related Disorders / Q000209:etiology / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D009609:Nitrous Oxide