title: Dopamine in the Brain: Hypothesizing Surfeit or Deficit Links to Reward and Addiction.
abstract: Recently there has been debate concerning the role of brain dopamine in reward and addiction. David Nutt and associates eloquently proposed that dopamine (DA) may be central to psycho stimulant dependence and some what important for alcohol, but not important for opiates, nicotine or even cannabis. Others have also argued that surfeit theories can explain for example cocaine seeking behavior as well as non-substance-related addictive behaviors. It seems prudent to distinguish between what constitutes "surfeit" compared to" deficit" in terms of short-term (acute) and long-term (chronic) brain reward circuitry responsivity. In an attempt to resolve controversy regarding the contributions of mesolimbic DA systems to reward, we review the three main competing explanatory categories: "liking", "learning", and "wanting". They are (a) the hedonic impact -liking reward, (b) the ability to predict rewarding effects-learning and (c) the incentive salience of reward-related stimuli -wanting. In terms of acute effects, most of the evidence seems to favor the "surfeit theory". Due to preferential dopamine release at mesolimbic-VTA-caudate-accumbens loci most drugs of abuse and Reward Deficiency Syndrome (RDS) behaviors have been linked to heightened feelings of well-being and hyperdopaminergic states.The "dopamine hypotheses" originally thought to be simple, is now believed to be quite complex and involves encoding the set point of hedonic tone, encoding attention, reward expectancy, and incentive motivation. Importantly, Willuhn et al. shows that in a self-administration paradigm, (chronic) excessive use of cocaine is caused by decreased phasic dopamine signaling in the striatum. In terms of chronic addictions, others have shown a blunted responsivity at brain reward sites with food, nicotine, and even gambling behavior. Finally, we are cognizant of the differences in dopaminergic function as addiction progresses and argue that relapse may be tied to dopamine deficiency. Vulnerability to addiction and relapse may be the result of the cumulative effects of dopaminergic and other neurotransmitter genetic variants and elevated stress levels. We therefore propose that dopamine homeostasis may be a preferred goal to combat relapse.
authors.affiliation: Department of Psychiatry and McKnight Brain Institute, University of Florida, College of Medicine, Gainesville, FL, USA; Division of Nutrigenomics, La Vita RDS, Salt Lake City, UT, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Blum
authors.affiliation: Research Institute on Addictions, University of Buffalo, State University of New York, Buffalo, NY, USA.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Thanos
authors.affiliation: Departments of Psychiatry, Neurology, and Anatomy & Neurobiology, Boston University School of Medicine, and Boston VA Healthcare System, Boston, MA, USA.
authors.forename: Marlene
authors.initials: M
authors.lastname: Oscar-Berman
authors.affiliation: Department of Psychiatry and McKnight Brain Institute, University of Florida, College of Medicine, Gainesville, FL, USA.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Febo
authors.affiliation: Departments of Psychiatry & Behavioral Sciences, Keck School of Medicine of USC, Los Angeles, CA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Baron
authors.affiliation: Department of Psychiatry, University of Minnesota School of Medicine, Minneapolis, MN, USA.
authors.forename: Rajendra D
authors.initials: RD
authors.lastname: Badgaiyan
authors.affiliation: Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Eliot
authors.initials: E
authors.lastname: Gardner
authors.affiliation: Eotvos Lorand University, Institute of Psychology, Department of Clinical Psychology and Addiction, Izabella utca 46., H-1064, Budapest, Hungary.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Demetrovics
authors.affiliation: Department of Psychology, University of Gothenburg, Sweden.
authors.forename: Claudia
authors.initials: C
authors.lastname: Fahlke
authors.affiliation: Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA.
authors.forename: Brett C
authors.initials: BC
authors.lastname: Haberstick
authors.affiliation: Department of Neurological Research, Path Foundation NY, USA.
authors.forename: Kristina
authors.initials: K
authors.lastname: Dushaj
authors.affiliation: Departments of Psychiatry, Neurology, and Anatomy & Neurobiology, Boston University School of Medicine, and Boston VA Healthcare System, Boston, MA, USA; Department of Psychiatry, Washington University School of Medicine. St. Louis, MO, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Gold
keywords: Dopamine receptors; Incentive salience; Learning; Liking and wanting; Neurogenetics; Reward deficiency syndrome; Surfeit