Imaging Dopamine Release in Depression

Study Overview
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Brief Summary
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This study aims to determine whether ventral striatal dopamine release is a mechanism of reward motivation in major depression, whether dopamine release is low in depression, and whether DA release and reward motivation predict response to dopamine-targeted treatment with pramipexole.

Detailed Description
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Better understanding of the basic neurobiology of mood dysfunction appears necessary to enable further progress in the treatment of depression. Reward motivation (and the closely related construct of reward learning) is a core neurobehavioral domain.(1,2) In major depressive disorder (MDD), low reward motivation is a key aspect of anhedonia, a cardinal symptom of MDD, and is related to resistance to treatment.(2,3) Although much has been learned about reward motivation's neurobiology and relevance to psychopathology, important gaps in our knowledge have impeded the application of basic science findings to improving treatment of MDD. Reward motivation in healthy subjects involves ventrostriatal (VST) dopamine (DA)(4,5), and reduced reward motivation is linked to MDD and anhedonia.(3,6) These data suggest that VST DA dysfunction might be present in MDD and manifested clinically by anhedonia. While DA neuroreceptor imaging studies have failed to verify this, they have been methodologically compromised. Limitations include imaging methods with poor resolution of functional striatal subregions, MDD samples heterogeneous for antidepressant use, and use of self-report measures of anhedonia, rather than objective behavioral testing of the specific domain of reward motivation. This will be the first study of both VST DA release (by PET imaging) and reward motivation, and will include patients with MDD and healthy volunteers. Reward motivation will be captured and operationalized as reward learning in a probabilistic reward task (prior to imaging). This will clarify if VST DA dysfunction is linked to impaired motivation in MDD. To test clinical implications in MDD patients, we will assess the relationship of VST DA release, reward motivation, and anhedonia to outcome of subsequent open label treatment with the DA D2 receptor agonist pramipexole.

Official Title
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Ventrostriatal Dopamine Release and Reward Motivation in MDD

Conditions
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Major Depressive Disorder

Intervention / Treatment
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* Drug: Pramipexole


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Weight between 44 kg and 115 kg Meets DSM-IV criteria for principal diagnosis of MDD, current major depressive episode, without psychotic features Score of >16 and <29 on 17-item Hamilton Rating Scale for Depression Psychotropic-naïve, as defined by lifetime <2 weeks treatment with antidepressants, anxiolytics or antipsychotics Able to tolerate a treatment-free period during study participation Able to provide informed consent Exclusion Criteria: A principal diagnosis of any current Axis I psychiatric disorder other than the MDD Lifetime diagnosis of any psychotic disorder, bipolar disorder, mental retardation, attention deficit/hyperactivity disorder, or substance use disorders (including nicotine use disorders) Serious suicidal risk or history of violent behavior which would make participation in the protocol unsafe Any tobacco use in the prior three months (if not already excluded for abuse/dependence by #1) Illicit drug use in the prior three months, as evidenced by history or urine toxicology screen Women who are pregnant, nursing, postmenopausal, or using hormonal methods of birth control Women who are not using an effective birth control method or sexual abstinence during the ten days before the scan Any medical or neurological problem that might affect interpretation of findings or safety of participation (e.g., blood dyscrasias, lymphomas, hypersplenism, endocrinopathies, renal failure or chronic obstructive lung disease, malignancy, neurological diseases of the brain, history of seizures or head trauma), low hemoglobin (Hb < 12 gm/dL in males, Hb < 10.5 gm/dL in females)) Blood donation within 4 weeks of study Metal implants or paramagnetic objects in the body that might affect safety of undergoing MRI (e.g., heart pacemaker, shrapnel, bullets, surgical prostheses or surgical clips), as determined in consultation with a neuroradiologist and according to the guidelines set forth in the reference: Guide to MR procedures and metallic objects Shellock; Lippincott Williams and Wilkins, NY, 2001 More than one major risk factor for coronary artery disease (e.g. hyperlipidemia, sedentary lifestyle). Smokers are already excluded by #4 above, and diabetics by #8 above Systolic blood pressure > 140 or diastolic blood pressure > 90 based on at least two readings at rest History of untoward reaction to amphetamine or other stimulant medication, or pramipexole Any psychotropic treatment in the past 3 weeks (or depot medication in the past 6 months), except for lorazepam,which may be administered as needed prior to imaging day Current, past or anticipated exposure to radiation in the workplace, or participation in nuclear medicine procedures, including research protocols (In case of previous exposure to activity due to research studies, subjects will be eligible if all conditions listed below are fulfilled: 1) The injected dose and dosimetry of the radiotracer are known; 2) Except for research studies, the subject has not been exposed to radiation (workplace and medical); 3) Adding prior exposure to the exposure due to the study will result in a yearly cumulative exposure lower than the FDA limit for research studies Family history of schizophrenia in parents, siblings, or children Ongoing cognitive-behavioral or interpersonal psychotherapy for depression (Supportive therapy is not an exclusion) Ongoing treatment with cimetidine

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Pramipexole<br>Six weeks of treatment with oral pramipexole, initiated at 0.25 mg/day and titrated to a maximum daily dose of 2.5 mg. | Drug: Pramipexole<br>* Dose will be started at 0.125 mg bid, and increased by 0.25 mg/day every 3-4 days to a target range of 1.0 - 2.5 mg/day.<br>* Other names: Mirapex (brand name);|
| No Intervention: Healthy Control<br>Healthy volunteers were matched to MDD group subjects by age, gender, and ethnicity, and will have no lifetime psychiatric disorders. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Hamilton Rating Scale for Depression | Hamilton Rating Scale for Depression (HRSD), 17-item version. This standard scale will be used to assess severity of depression, looking at change in total score from baseline to week 6, rating severity of depression on a scale from 0 (least depression) to 50 (greatest depression) | Baseline and 6 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Snaith Hamilton Pleasure Scale | Fourteen-item self-rated anhedonia scale. Items were comprised of statements that participants rated as strongly disagree (1), disagree (2), agree (3), or strongly agree (4). The lowest possible score was 14, the highest possible score was 56. | Baseline and 6 weeks | 
| Change in Temporal Experience of Pleasure Scale - Anticipatory Subscale | A validated self-rated scale shown to assess anticipatory pleasure. It will be used for exploratory analyses of anhedonia. 18 items were measured on a scale of 1 (very false for me) to 6 (very true for me). Higher scores indicate higher pleasure. Item scores were added for a lowest possible score of 18 and highest possible score of 108. | Baseline and 6 weeks | 
| Change in Mood and Anxiety Symptom Questionnaire, Short Form | Change in Mood and Anxiety Symptom Questionnaire, Short Form. A 62-item scale assessing anxiety and depression. Items were measured on a scale of 1-5, higher number indicating higher levels of symptoms.The lowest possible score was 62, and the highest 310. | Baseline and 6 weeks | 
| Change in the Apathy Evaluation Rating Scale | A validated self-rated 18 item scale assessing apathy. Items were rated from 1 (not at all true) to 4 (very true). Higher scores indicate lower apathy, lower scores indicate higher apathy. Lowest possible score is 18, highest possible score is 72. | Baseline and 6 weeks | 
| Change in Clinical Global Improvement - Severity Scale | Seven-point Likert scale rating clinical severity of mental illness from 1 (least severe) to 7 ( most severe). Physician-rated scale. One item. | 6 weeks | 
| Change in Temporal Experiences of Pleasure Scale -- Consummatory Subscale | A validated self-rated scale shown to assess consummatory pleasure. It will be used for exploratory analyses of anhedonia. 18 items were measured on a scale of 1 (very false for me) to 6 (very true for me). Higher scores indicate higher pleasure. Item scores were added for a lowest possible score of 18 and highest possible score of 108. | Baseline and 6 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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MDD, Major depressive disorder, depression, pramipexole