characterize the modulatory effects of dopamine d2/d3 receptor agonist and antagonist drugs on compulsive behaviors

Conditions: Obsessive-Compulsive Disorder

Summary: 3 groups of subjects (healthy controls, ocd subjects and stimulant-dependent subjects) will receive pramipexole (1.5 mg, single dose), amisulpride (400 mg, single dose) or placebo in a cross-over, double-blind, placebo-controlled design. effects of compulsive behaviour will be assessed using fmri and cognitive testing. assess biomarkers including cardiovascular responses and plasma levels. all groups studied on 3 separate occasions following screening, with at least a week intervening between consecutive assessments. the procedures to be adopted for study assessment will be identical on each occasion.


Eligibility criteria:
inclusion criteria: * male or female, between 18 - 55 years of age; the groups will be matched for either handedness. * participants must have the ability to comprehend the key components of the consent form and provide informed consent. * participants must lead and write (in english) at a level sufficient to complete study related assessments. * assessment by a psychiatrist or psychologist, which includes a face-to-face evaluation of the individual using the dsm-vi diagnosis. * no history of neurological disorder, head/brain injury, hepatitis, or visual impairment. * no mri contra-indications (metal in body, claustrophobia) and able to provide blood samples (venous accessibility, especially relevant for drug users). * patients with obsessive-compulsive disorder will have a minimum 2-year history of compulsive behaviours satisfying dsm-iv-tr criteria for ocd. * participants with chronic stimulant use will have a minimum 2-year history of dependence on class a stimulants, with age of drug abuse onset before 20 years, and will satisfy dsm-iv-tr criteria for dependence on stimulant drugs. * control volunteers have to be in good mental and physical health. exclusion criteria: * a personal history of psychiatric or neurological disorders, as defined by the dsmiv (except ocd in patients with ocd and substance dependence in drug users) * a history or presence of alcohol / substance abuse or dependence (other than nicotine), as defined by the dsm-iv-tr (except drug dependence group). * a bdi-ii total score greater than 14 will lead to exclusion from the study. * treatment with methadone or buprenorphine may interfere with the experimental tasks, and therefore, will lead to exclusion from the study. * participants who have any laboratory abnormality that in the investigator's judgement is considered to be clinically significant and could potentially affect subject safety or study outcome. * history of clinically significant or current renal dysfunction. * clinically significant abnormalities in hematology, blood chemistry, mri, urinalysis or physical examination not resolved by baseline visit. * impaired liver function at baseline or history of liver dysfunction. * female participant is pregnant or currently breastfeeding. * any serious medical disorder or condition that would in the investigator's opinion, preclude the administration of study medication and or a history of clinically significant hepatic, cardiac, renal, neurologic, cerebrovascular, metabolic or pulmonary disease.

Keywords: dopamine ocd mri stimulant users