OBJECTIVE: There is an impressive literature implicating abnormalities
in serotonergic neural systems in depression. Many investigators, but not
all, have reported low numbers of platelet and brain serotonin (5- HT)
transporter sites in drug-free depressed patients. In the present study the
authors sought to determine whether the low platelet 5-HT transporter
binding in depressed patients is due to previous antidepressant drug
exposure. In addition, the binding of both [3H]imipramine and the more
specific ligand [3H]paroxetine to the platelet 5-HT transporter was
compared in drug-free depressed patients and age- and sex-matched normal
comparison subjects. METHOD: In the first experiment blood samples were
obtained from 12 depressed patients who had never received antidepressant
drugs and 12 normal comparison subjects, and platelet 5-HT transporter
binding was measured by using [3H]imipramine. In the second experiment
blood samples were obtained from 28 drug-free depressed patients and 28
age- and sex-matched comparison subjects, and platelet 5-HT transporter
binding was assessed by using both [3H]imipramine and [3H]paroxetine.
RESULTS: In the first experiment the never-medicated depressed patients
exhibited fewer platelet [3H]imipramine binding sites than did the
comparison subjects. In the second experiment the drug-free depressed
patients had fewer platelet binding sites for both [3H]imipramine and
[3H]paroxetine than did the comparison subjects. CONCLUSIONS: The low
number of platelet [3H]imipramine binding sites does not appear to be due
to prior antidepressant drug exposure. The Bmax of platelet binding sites
for both [3H]imipramine and [3H]paroxetine, ligands used to measure 5-HT
transporter binding, is abnormally low in depressed patients.Abstract Teaser