Neuroimaging of St. John's Wort-Induced Changes of Serotonin Metabolism in Normal Subjects
Status:
Completed
Trial end date:
2002-06-01
Target enrollment:
Participant gender:
Summary
St. John's Wort is a popular dietary supplement that many people take to elevate mood or
relieve stress. This study will test in normal volunteers whether this preparation may alter
mood and if so, by what means. Animal studies suggest that St. John's Wort may work similarly
to some antidepressants that affect levels of the chemical serotonin in the brain.
Participants in this study must also be enrolled in NIMH protocol #98-M-0094 (SPECT Imaging
of Dopamine and Serotonin Transporters in Neuropsychiatric Patients and Normal Volunteers)
and protocol #91-M-014 (MRI Imaging of Neuropsychiatric Patients and Controls). Separate
consent forms are required for each study. Candidates will undergo medical and psychiatric
evaluations that may include blood and urine tests, electroencephalogram and
electrocardiogram.
Normal volunteers will have a mood assessment at the beginning of the study. They will then
be randomly assigned to take either placebo (a pill with no active ingredient) or St. John's
Wort 3 times a day for 2 weeks, and will be told what they are taking. After an 11-week
hiatus, they will again start treatment on the same schedule, but will not be told which
preparation they are receiving. Each evening during the 2-week treatment periods, subjects
will complete a brief self-rating mood assessment questionnaire. At the end of each treatment
period, they will undergo SPECT brain imaging (a type of CT scan) to determine dopamine and
serotonin distribution and density in the brain.
For this procedure, study subjects take three drops of potassium iodide solution within 24
hours before the scan and two drops nightly for 3 days following the procedure. About 10 ml
(less than two teaspoons) of blood are drawn before a radioactive tracer is injected. SPECT
imaging is done the next day. After about 1 hour of imaging, subjects are given either a
placebo or St. John's Wort, and then imaging continues for another 2 hours. During the
procedure, up to five blood samples of 6 ml each may be drawn. At some point during the
study, a MRI scan of the brain will be done.