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Dopamine Responsivity in Gamblers

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT02772978
Recruitment Status : Completed
First Posted : May 16, 2016
Results First Posted : February 16, 2021
Last Update Posted : February 16, 2021
National Center for Responsible Gaming
Information provided by (Responsible Party):
University of California, San Francisco

Brief Summary:
This study deals with how people decide between rewards of different value. The investigators want to understand how the brain's dopamine system impacts this kind of decision making. The investigators will use a medication, tolcapone, which can temporarily affect the dopamine system.

Condition or disease Intervention/treatment Phase
Pathological Gambling Drug: Tolcapone Drug: Placebo Not Applicable

Detailed Description:
Tolcapone increases the effects of dopamine in the brain. Dopamine is a substance that is normally present in the brain. It may increase body movement and may also change a person's ability to process information. Tolcapone stops one's own naturally-released dopamine from being broken down as quickly. The investigators are interested in learning if tolcapone has positive effects on a person's decisions about rewards.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 19 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Intervention Model Description: This study is a single-group study in which subjects received both placebo and tolcapone in a randomized, double-blind, counterbalanced, within-subject design.
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Basic Science
Official Title: A Randomized, Double-Blind Study of Neural Circuit Responses to COMT Inhibitors in PPG
Study Start Date : August 2014
Actual Primary Completion Date : September 2015
Actual Study Completion Date : September 2015

Resource links provided by the National Library of Medicine

Drug Information available for: Tolcapone

Arm Intervention/treatment
Active Comparator: tolcapone arm
This cognitive science study consists of a single "arm" in which all subjects receive both tolcapone and placebo in randomized, double-blind, counterbalanced, crossover fashion
Drug: Tolcapone
Tolcapone is in the medication class of catechol-O-methyltransferase (COMT) inhibitors
Other Name: Tasmar

Placebo Comparator: placebo arm
This cognitive science study consists of a single "arm" in which all subjects receive both tolcapone and placebo in randomized, double-blind, counterbalanced, crossover fashion
Drug: Placebo
A placebo is a tablet or capsule that looks like the study medication (in this case, tolcapone) but does not contain any active ingredients
Other Name: Sugar pill

Primary Outcome Measures :
  1. Correlation Between the Impulsive Choice Ratio and Baseline Impulsivity, as Measured With the Barratt Impulsiveness Scale, Non-planning Subscale [ Time Frame: 120 minutes after drug ingestion ]
    The presented value represents a correlation. Subjects completed a delay discounting task while functional MRI images were obtained. In this task, subjects made hypothetical choices between a smaller amount of money available sooner, and a larger amount of money available later. Performance on the delay discounting task, as assessed by the impulsive choice ratio, was determined for both the tolcapone and placebo sessions, and the difference between them (tolcapone minus placebo) was calculated. This difference value was then correlated with scores on the Barratt Impulsiveness Scale, non-planning subscale.

Other Outcome Measures:
  1. Correlation Between the Difference in ICR (Tolcapone Minus Placebo) and the Difference in Blood Oxygen Level Dependent (BOLD) Signal in the Brain (Tolcapone Minus Placebo) [ Time Frame: 120 minutes after drug ingestion ]
    The presented value represents a correlation. The difference in performance on the delay discounting task was calculated as the change in ICR (tolcapone minus placebo). In addition, the difference in BOLD activity throughout the brain was determined (tolcapone minus placebo).

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria: This behavioral and fMRI study will recruit alcohol drinkers who also participate in gambling activities. Subjects will be selected in an unbiased fashion with respect to gender and ethnicity, as minority representation issues do not interact with any of the hypotheses. To be eligible to participate in the study, the following inclusion criteria must also be met:

  1. Subject is a healthy volunteer between 18-50 years of age.
  2. Subject is right handed (important for interpreting MRI activity).
  3. If female, subject is non-lactating, not pregnant and using a reliable contraception method (i.e. abstinence, intrauterine device, hormonal birth control or barrier method).
  4. Subject is able to read and speak English.
  5. Subject is a high school graduate.
  6. Subject is able and willing to provide written informed consent.
  7. Subject is able to understand and follow the instructions of the investigator, and understand all ratings scales.
  8. Subject is in good health.

Exclusion Criteria:

• In order to assess potential contraindications to tolcapone, blood will be tested for routine chemistries including white cell count, red cell count, platelet count, hemoglobin, hematocrit, MCV, MCH, MCHC, RDW, neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Additionally, a hepatic screen will assay total protein, albumin, globulin, A/G ratio, bilirubin (total, direct, and indirect), alkaline phosphatase, AST (SGOT), and ALT (SGPT). Elevation of plasma bilirubin, AST (SGOT), ALT (SGPT), or alkaline phosphatase consistent with liver disease will be grounds for subject exclusion. (Note that ongoing monitoring of liver enzymes will not be necessary, as only a single, counterbalanced dose of tolcapone will be administered to each subject.) Subjects will additionally be urine-screened for illicit drug use and screened for alcohol intoxication via breathalyzer. The 7 drug classes detected include cocaine, amphetamine, methamphetamine, benzodiazepines, THC, opiates & oxycodone. These drugs have been chosen due to their possible interaction with tolcapone and possible cognitive and cardiovascular effects. No identifiers will be put on the test cup and it will be read immediately and discarded by the researcher. Similarly, the results of the breathalyzer will be read and then the test will be discarded. No personal identifiers will be associated with the test results. Subjects who test positive for any of these substances, with the exception of THC, will be excluded from further participation in the study. Subjects who have used any psychoactive drugs (except marijuana) within 2 weeks of the start of the study or more than 10 times in the last year will be excluded from participation in the study.

Subjects will also be excluded if they regularly use medications that affect dopamine levels, or will have used these medications within two weeks of tolcapone administration (such as tolcapone, entacapone, or any of the following: levodopa/carbidopa, amantadine, bromocriptine, pergolide, pramipexole, ropinirole, selegeline, isocarboxazid, phenelzine, tranylcypromine, clozapine, olanzapine, quetiapine, risperidone, ziprasidone, aripiprazole, fluphenazine, haloperidol, perphenazine, pimozide, thiothixene, trifluoperazine, loxapine, molindone, chlorpromazine, mesoridazine, thioridazine, dextroamphetamine, dexmethylphenidate, dextroamphetamine, or methylphenidate).

A licensed health care provider will also conduct a brief physical exam. This exam will search for signs of medical illness, including jaundice or abdominal distension associated with liver disease, that would exclude subjects from participating in the study. Subjects with clinically significant medical or psychiatric illnesses requiring treatment as determined by screening blood tests, medical history, and/or physical exam will not be eligible to participate in the study.

Female subjects will also be screened for pregnancy, as the effects of COMT inhibitors during pregnancy are not adequately known and these compounds can appear in breast milk. (Pregnancy is also a contraindication to MRI scanning). Since subjects may not know they are pregnant, all female subjects recruited to participate in the study will be required to have a urine pregnancy test prior to each session of the study. These requirements will not apply to any female subjects who are post-menopausal.

Active use of substances other than alcohol, tobacco, or marijuana, use of alcohol on the day of the meeting as assessed by breathalyzer testing, reported marijuana use in the 48 hours preceding a testing visit, and/or a positive pregnancy test, will be grounds for exclusion.

For subjects participating in the fMRI, we will administer an extensive questionnaire listing contraindications to MRI scanning. Because the MRI scanner attracts certain metals, subjects who may have metallic objects in their bodies will be excluded. As an additional measure of protection, we will use a hand-held metal detector to screen subjects before entering the scanner. Subjects who experience claustrophobia will also be excluded from participating in the MRI scan.

Known allergy or intolerance to tolcapone or use of an investigational drug within 30 days of the screening visit will be grounds for exclusion.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT02772978

Sponsors and Collaborators
University of California, San Francisco
National Center for Responsible Gaming
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Principal Investigator: Andrew Kayser, MD, PhD University of California at San Francisco
Publications of Results:
Other Publications:
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Responsible Party: University of California, San Francisco Identifier: NCT02772978    
Other Study ID Numbers: 10-03082 UCSF
First Posted: May 16, 2016    Key Record Dates
Results First Posted: February 16, 2021
Last Update Posted: February 16, 2021
Last Verified: February 2021
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No
Keywords provided by University of California, San Francisco:
decision making
Additional relevant MeSH terms:
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Disruptive, Impulse Control, and Conduct Disorders
Mental Disorders
Antiparkinson Agents
Anti-Dyskinesia Agents
Catechol O-Methyltransferase Inhibitors
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action