The Role of Norepinephrine in Emotional Processing
This study will examine the role of a brain chemical called norepinephrine in thinking, decision-making, and emotional processing. After norepinephrine is released from a brain cell, it binds to another brain cell's receptor. Some of the receptors it binds to are called alpha-2 adrenergic receptors. This study will use medicines called yohimbine and guanfacine to look at the function of norepinephrine in the brain when it binds to the alpha-2 adrenergic receptors. Yohimbine increases norepinephrine's function and guanfacine decreases its function.
Healthy volunteers between 20 and 50 years of age who do not have heart disease, high blood pressure, psychiatric illness, or other serious medical conditions and who are not allergic to lactose may be eligible for this study. Candidates are screened with a medical and psychiatric history, physical examination, neuropsychological testing, blood and urine tests and electrocardiogram. Women are screened with a urine pregnancy test.
Participants are given a pill of yohimbine, guanfacine, or placebo and undergo the following tests and procedures:
- Blood pressure and heart rate measurements: Blood pressure and heart rate are measured before the medication is taken and several times after.
- Blood draws: Blood is drawn before the medicine is taken and 90 minutes after to measure levels of norepinephrine and the hormone cortisol.
- Neurocognitive testing: Participants do neurocognitive tasks on the computer for up to 90 minutes. The tasks involve looking at pictures or words on a screen and responding according to instructions given.
- Magnetic resonance imaging (MRI): Patients may undergo neurocognitive testing MRIs. This test uses a strong magnetic field and radio waves to show changes in brain activity. The subject lies on a table that slides into a narrow cylinder (the MRI scanner). Images of the brain are obtained while the subject performs the computer tasks.
|Official Title:||Investigating the Role of Norepinephrine in Emotional Processing Through Alpha-2 Adrenergic Receptor Modulation|
|Study Start Date:||April 2005|
|Study Completion Date:||March 2009|
|Primary Completion Date:||March 2009 (Final data collection date for primary outcome measure)|
An understanding of the role of specific neurotransmitters in the neurocognitive functions mediating emotional processing is essential for the understanding and treatment of mood and anxiety disorders. One such disorder, currently regarded as untreatable, is psychopathy. Psychopathy has been linked with noradrenergic and amygdala disturbances. However, an understanding of the functional significance of the noradrenergic system in humans remains in its infancy. The goal of this protocol is to use targeted noradrenergic manipulations (yohimbine and guanfacine) in conjunction with specific neurocognitive and neuroimaging paradigms to consider the role of norepinephrine in reward and punishment processing. In particular, we wish to evaluate the hypothesis that increased norepinephrine levels following the administration of yohimbine will lead to enhanced formation and processing of stimulus-reward and stimulus-punishment associations, while decreased norepinephrine levels following the administration of guanfacine will reduce the formation and processing of stimulus-reward and stimulus-punishment associations. In addition, we aim to examine the hypothesis that increased norepinephrine levels will lead to increased neural response in the amygdala during either the formation, or processing, of stimulus-reinforcement associations.
Please refer to this study by its ClinicalTrials.gov identifier: NCT00109642
|United States, Maryland|
|National Institutes of Health Clinical Center, 9000 Rockville Pike|
|Bethesda, Maryland, United States, 20892|