The Effects of Acute Dopamine Precursor Depletion on the Reinforcing Value of Exercise in Anorexia Nervosa

PLoS One. 2016 Jan 25;11(1):e0145894. doi: 10.1371/journal.pone.0145894. eCollection 2016.

Abstract

This study investigated whether dopaminergic systems are involved in the motivation to engage in behaviours associated with anorexia nervosa (AN), specifically, the drive to exercise. Women recovered from AN (AN REC, n = 17) and healthy controls (HC, n = 15) were recruited. The acute phenylalanine/tyrosine depletion (APTD) method was used to transiently decrease dopamine synthesis and transmission. The effect of dopamine precursor depletion on drive to exercise was measured using a progressive ratio (PR) exercise breakpoint task. Both groups worked for the opportunity to exercise, and, at baseline, PR breakpoint scores were higher in AN REC than HC. Compared to values on the experimental control session, APTD did not decrease PR breakpoint scores in AN REC, but significantly decreased scores in HC. These data show that women recovered from AN are more motivated to exercise than HC, although in both groups, activity is more reinforcing than inactivity. Importantly, decreasing dopamine does not reduce the motivation to exercise in people recovered from AN, but in contrast, does so in HC. It is proposed that in AN, drive to exercise develops into a behaviour that is largely independent of dopamine mediated reward processes and becomes dependent on cortico-striatal neurocircuitry that regulates automated, habit- or compulsive-like behaviours. These data strengthen the case for the involvement of reward, learning, habit, and dopaminergic systems in the aetiology of AN.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Affect
  • Anorexia Nervosa / physiopathology*
  • Anorexia Nervosa / psychology
  • Case-Control Studies
  • Convalescence
  • Diet, Protein-Restricted
  • Dopamine / biosynthesis
  • Dopamine / physiology*
  • Drive*
  • Exercise / physiology*
  • Female
  • Humans
  • Motivation
  • Phenylalanine / administration & dosage
  • Phenylalanine / blood
  • Reward*
  • Self Report
  • Surveys and Questionnaires
  • Tyrosine / administration & dosage
  • Tyrosine / blood
  • Video Games
  • Young Adult

Substances

  • Tyrosine
  • Phenylalanine
  • Dopamine

Grants and funding

This study was supported by the Swiss Anorexia Foundation (project number 10-11) and by the NIHR Biomedical Research Centre (BRC) for Mental Health at South London and Maudsley NHS Foundation Trust and King’s College London (grant number 12421). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. Iain Campbell and Ulrike Schmidt receive salary support from the BRC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.