Abstract
Background: Prior research has suggested reductions in the density of serotonin transporter (SERT) binding sites in blood platelets and post-mortem brain tissue of depressed patients. We sought to determine whether patients with unipolar major depression have diminished SERT availability as assessed by both brainstem [
123I]β-CIT SPECT and platelet [
3H]paroxetine binding.
Methods: Drug-free depressed and healthy subjects were injected with 211 ± 22 MBq [
123I]β-CIT and imaged 24 ± 2 h later under equilibrium conditions. A ratio of specific to nonspecific brain uptake (V
3″ = (brainstem-occipital)/occipital), a measure proportional to the binding potential (B
max/K
d), was used for all comparisons.
Results: Results showed a statistically significant reduction in brainstem V
3″ values in depressed as compared to healthy subjects (3.1 ± .9 vs. 3.8 ± .8, p = .02). Platelet [
3H]paroxetine binding was not altered (B
max = 2389 ± 484 vs. 2415 ± 538 fmol/mg protein,
p = .91) and was not significantly correlated with brainstem [
123I]β-CIT binding (
r = −0.14,
p = .48).
Conclusions: These data are the first to suggest reductions in the density of brain SERT binding sites in living depressed patients. These findings provide further support for a preeminent role for alterations in serotonergic neurons in the pathophysiology of depression.
