Tritiated imipramine binding. A peripheral marker for serotonin in Parkinson's disease
M. Sano, M. Stanley, A. Lawton, L. Cote, J. Williams, Y. Stern, K. Marder and R. Mayeux
Department of Neurology, Columbia University, College of Physicians and Surgeons, New York, NY.
Tritiated imipramine binding in platelets has been used to evaluate
serotonin activity in depression in previous studies. This article examined
this marker as a possible measure of central nervous system serotonergic
activity for depression in patients with Parkinson's disease (PD). The
number of binding sites was significantly lower in depressed patients with
PD than in a healthy control group. Patients with PD who were not depressed
had lower values than the comparison group, but this difference was not
significant. We also found a significant correlation between the receptor
site values in platelets and cerebrospinal fluid levels of the serotonin
metabolite, 5-hydroxyindoleacetic acid (r = .59), but this was independent
of a diagnosis of depression. Receptor site values were examined to
identify appropriate cutoff scores to predict depression in the group of
patients with PD. A maximum sensitivity of 50% was achieved with a
specificity of 64%. Our results strongly support a generalized alteration
in serotonin metabolism in depressed patients with PD, but tritiated
imipramine binding in platelets is not a useful diagnostic tool for
depression.