title: Reduced neural response to reward following 7 days treatment with the cannabinoid CB1 antagonist rimonabant in healthy volunteers.
abstract: Reduced subjective experience of reward (anhedonia) is a key symptom of major depression. The anti-obesity drug and cannabinoid type 1 receptor (CB(1)) antagonist, rimonabant, is associated with significant rates of depression and anxiety in clinical use and was recently withdrawn from the market because of these adverse effects. Using a functional magnetic resonance imaging (fMRI) model of reward we hypothesized that rimonabant would impair reward processing. Twenty-two healthy participants were randomly allocated to receive rimonabant (20 mg), or placebo, for 7 d in a double-blind, parallel group design. We used fMRI to measure the neural response to rewarding (sight and/or flavour of chocolate) and aversive (sight of mouldy strawberries and/or an unpleasant strawberry taste) stimuli on the final day of drug treatment. Rimonabant reduced the neural response to chocolate stimuli in key reward areas such as the ventral striatum and the orbitofrontal cortex. Rimonabant also decreased neural responses to the aversive stimulus condition in the caudate nucleus and ventral striatum, but increased lateral orbitofrontal activations to the aversive sight and taste of strawberry condition. Our findings are the first to show that the anti-obesity drug rimonabant inhibits the neural processing of rewarding food stimuli in humans. This plausibly underlies its ability to promote weight loss, but may also indicate a mechanism for inducing anhedonia which could lead to the increased risk of depressive symptomatology seen in clinical use. fMRI may be a useful method of screening novel agents for unwanted effects on reward and associated clinical adverse reactions.
authors.affiliation: University Department of Psychiatry, Warneford Hospital, Oxford, UK.
authors.forename: Jamie
authors.initials: J
authors.lastname: Horder
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Harmer
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Cowen
authors.forename: Ciara
authors.initials: C
authors.lastname: McCabe
mesh_terms: D000293:Adolescent; D000328:Adult; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D002186:Cannabinoids / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002421:Caudate Nucleus / Q000187:drug effects* / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010880:Piperidines / Q000008:administration & dosage*; D011720:Pyrazoles / Q000008:administration & dosage*; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012201:Reward; D000077285:Rimonabant; D013649:Taste / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D002186:Cannabinoids; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D000077285:Rimonabant