1. ¹Clinical Neuroscience Section, Centre for Addiction and Mental Health, Toronto, ON, Canada
2. ²Department of Pharmacology, University of Toronto, Toronto, ON, Canada
3. ³Department of Public Health Sciences, University of Toronto, Toronto, ON, Canada
4. ⁴Department of Psychology, University of Toronto, Toronto, ON, Canada

Correspondence: Dr M Zack, Clinical Neuroscience Section, Centre for Addiction and Mental Health, 33 Russell Street, Toronto, ON, Canada M5S 2S1. Tel: +1 416 535 8501, ext. 6052; Fax: +1 416 595 6618, E-mail: martin_zack@camh.net

Received 1 June 2006; Revised 16 October 2006; Accepted 2 November 2006; Published online 3 January 2007.

Abstract

Previous research indicated shared neurochemical substrates for gambling and psychostimulant reward. This suggests that dopamine substrates may directly govern the reinforcement process in pathological gambling. To investigate this issue, the present study assessed the effects of the relatively selective dopamine D2 antagonist, haloperidol (3 mg, oral) on responses to actual gambling (15 min on a slot machine) in 20 non-comorbid pathological gamblers and 18 non-gambler controls in a placebo-controlled, double-blind, counterbalanced design. In gamblers, haloperidol significantly increased self-reported rewarding effects of gambling, post-game priming of desire to gamble, facilitation of reading speed to Gambling words, and gambling-induced elevation in blood pressure. In controls, haloperidol augmented gambling-induced elevation in blood pressure, but had no effect on other indices. The findings provide direct experimental evidence that the D2 substrate modulates gambling reinforcement in pathological gamblers.