Investigating the Role of Serotonin in Emotional Processing Through the Use of Tryptophan Depletion

This study will examine the role of serotonin function in the brain. Serotonin, one of the brain's natural chemicals, connects with receptors on brain cells to regulate emotion, anxiety, sleep, stress hormones, and other body functions that are disturbed in various mood and anxiety disorders. Also, the research will look at the function of particular brain areas, how they are involved in regulating emotions, and how serotonin is involved in the regulation of their function. The procedures entailed are tryptophan depletion and magnetic resonance imagining (MRI). Also, researchers' understanding of the genetic causes of mood and anxiety disorders will increase through examination of participants' DNA.

Adults in good health, ages 20 through 50, may be eligible for this study. Among those not eligible are females who are pregnant or breast feeding, patients with psychiatric or central nervous system disease, and those taking medications that would interfere with study results.

At the first visit, patients will be asked about their general mood, degree of nervousness, thinking skills, and behavior. The session will last from 1.5 to 2.0 hours. A blood sample of about 2 tablespoons will be drawn, for DNA study.

Participants will undergo the following procedures and tests:

• Physical examination.
• Test of vital signs, lying and standing.
• Electrocardiogram.
• Collection of blood for chemistry and hematology.
• Urinalysis.
• HIV, urine drug, and hepatitis screening.
• Psychiatric screening.
• (SqrRoot) -HCG pregnancy test, if applicable.

At the second visit, patients will receive either tryptophan depletion or placebo, and 5 hours later, the study will begin, to last up to 2 additional hours. Patients will be asked periodically about their emotional state or changes in their well-being. The MRI system will create images of the brain's blood flow and measure glucose metabolism as a measure of brain activity. During the MRI scan, patients will hear knocking or beeping sounds, and they will wear earplugs to reduce the noise. Patients will be able to communicate with the MRI staff at all times during the scan, and they may ask to be moved out of the machine at any time. The MRI session lasts up to 1.5 hours.

Results of any medical tests or other information will not be provided to participants, because further research may be needed before such results are meaningful. But if meaningful information develops from this study that may be important for a participant's health, he or she will be notified about it when it becomes available.