Dopamine and Opioid Receptor Antagonists Reduce Cue-induced Reward Responding and Reward Impulsivity
Condition: Addiction
MeSH terms: Impulsive Behavior
Study type: Interventional

Summary: 
      The purpose of this study is to determine how the dopamine and opioid system is involved in
      reward processing, specifically in cue-induced reward responding and reward impulsivity,
      using dopamine and opioid receptor antagonists in healthy participants. The investigators
      predict that particularly the dopamine challenge should alter cue-induced reward responding
      and reward impulsivity. Such effects would be of high interest for the treatment of disorders
      which involve impairments of reward processing such as addiction.
    

Detailed description: 
      In this study the investigators use amisulpride and naltrexone to elucidate what function the
      dopamine and opioid system have in the processing of reward. Amisulpride [Solian®;
      sanofi-aventis] is an atypical antipsychotic and acts as an antagonist at dopamine D2 and D3
      (D2/D3) receptors with very high specificity. Amisulpride has been used in numerous past
      studies to study the role of dopamine in the brain, for example in studies on reinforcement
      learning, memory, and attentional bias in stimulant dependence. Naltrexone [Naltrexin®; OrPha
      Swiss GmbH] is an opioid antagonist and is clinically used in the management of alcohol and
      opioid dependence. It has been used to investigate the role of opioid in pain perception,
      taste detection and recognition, and smoking behavior. The investigators were interested in
      particular how amisulpride and naltrexone influence cue-induced reward responding and reward
      impulsivity.

      Study Aims

      A) Investigating the role of the dopamine system in cue-induced reward responding; B)
      Investigating the role of the dopamine system in reward impulsivity; C) Investigating the
      role of the opioid system in cue-induced reward responding; A) Investigating the role of the
      opioid system in reward impulsivity.

      Study Design

      This is a double-blind, randomized, placebo-controlled, between-subject blocker study. 121
      participants received either placebo, the dopamine D2/D3 receptor antagonist amisulpride (400
      mg), or the unselective opioid receptor antagonist naltrexone (50 mg), 3h before the
      experimental tasks. Subjective effects on mood were assessed by visual analogue scales (VAS).
      Cue-induced reward responding was measured using a standard Pavlovian-to-Instrumental
      Transfer (PIT) task, where participants press a button for reward in the presence of a
      stimulus predicting that reward. Reward impulsivity was measured using a Delay Discounting
      (DD) Task, in which participants choose between smaller, immediate rewards and larger,
      delayed rewards.
    

Intervention name(s): Placebo; Amisulpride; Naltrexone
Intervention type(s): Drug; Drug; Drug
Intervention description(s): Placebo Pill; 400 mg Amisulpride; 50 mg Naltrexone
Other intervention name(s): Lactose Placebo Pill; Solian; Naltrexin
Intervention MeSH terms: Naltrexone; Amisulpride
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Keywords: Dopamine; Opioid; Reward