Opposing neural effects of naltrexone on food reward and aversion: implications for the treatment of obesity.
BACKGROUND
Opioid antagonism reduces the consumption of palatable foods in humans but the neural substrates implicated in these effects are less well understood.


OBJECTIVE
The aim of the present study was to examine the effects of the opioid antagonist, naltrexone, on neural response to rewarding and aversive sight and taste stimuli.


METHODS
We used functional magnetic resonance imaging (fMRI) to examine the neural responses to the sight and taste of pleasant (chocolate) and aversive (mouldy strawberry) stimuli in 20 healthy volunteers who received a single oral dose of naltrexone (50 mg) and placebo in a double-blind, repeated-measures cross-over, design.


RESULTS
Relative to placebo, naltrexone decreased reward activation to chocolate in the dorsal anterior cingulate cortex and caudate, and increased aversive-related activation to unpleasant strawberry in the amygdala and anterior insula.


CONCLUSIONS
These findings suggest that modulation of key brain areas involved in reward processing, cognitive control and habit formation such as the dorsal anterior cingulate cortex (dACC) and caudate might underlie reduction in food intake with opioid antagonism. Furthermore we show for the first time that naltrexone can increase activations related to aversive food stimuli. These results support further investigation of opioid treatments in obesity.
Department of Psychiatry, Warneford Hospital, University of Oxford, Neuroscience Building, Oxford, OX3 7JX, UK.
Elizabeth
E
Murray
Sietske
S
Brouwer
Rob
R
McCutcheon
Catherine J
CJ
Harmer
Philip J
PJ
Cowen
Ciara
C
McCabe
D000328:Adult; D000339:Affect / Q000187:drug effects; D001931:Brain Mapping; D054022:Cerebrum / Q000187:drug effects*; D004311:Double-Blind Method; D005260:Female; D005502:Food; D006801:Humans; D008279:Magnetic Resonance Imaging; D009271:Naltrexone / Q000008:administration & dosage / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D009765:Obesity / Q000188:drug therapy*; D012201:Reward; D013649:Taste / Q000187:drug effects; D055815:Young Adult
D009292:Narcotic Antagonists; D009271:Naltrexone