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The competition between endogenous transmitters and radiolabeled ligands for in vivo binding to neuroreceptors might provide a method to measure endogenous transmitter release in the living human brain with noninvasive techniques such as positron emission tomography (PET) or single photon emission computerized tomography (SPECT). In this study, we validated(More)
Low levels of dopamine beta-hydroxylase (DbetaH) protein in the plasma or cerebrospinal fluid (CSF) are associated with greater vulnerability to positive psychotic symptoms in several psychiatric disorders. DbetaH level is a stable, genetically controlled trait. DBH, the locus encoding DbetaH protein, is the major quantitative trait locus controlling plasma(More)
Prior research points to the importance of psychostimulants in improving self-control. However, the neural substrates underlying such improvement remain unclear. Here, in a pharmacological functional MRI study of the stop signal task, we show that methylphenidate (as compared with placebo) robustly decreased stop signal reaction time (SSRT), an index of(More)
UNLABELLED The effect of age on human striatal dopamine (DA) transporters was investigated with SPECT using the ligand [123I]2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([123I]beta-CIT). METHODS Iodine-123-beta-CIT binding in the striatum was examined in 28 healthy human subjects (14 men, 14 women) who ranged in age from 18 to 83 yr. Following(More)
BACKGROUND Attention-deficit/hyperactivity disorder is a psychiatric disorder that starts in childhood. The mechanism of action of methylphenidate, the most common treatment for attention deficit hyperactivity disorder, is unclear. In vitro, the affinity of methylphenidate for the norepinephrine transporter (NET) is higher than that for the dopamine(More)
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] beta-CIT SPECT and platelet(More)
BACKGROUND Short-term depletion of plasma tryptophan has been shown to result in depressive relapse in patients with remission of major depression. Positron emission tomography and single photon emission computed tomography studies implicated the dorsolateral prefrontal cortex, orbitofrontal cortex, thalamus, and caudate nucleus in the pathogenesis of(More)
UNLABELLED A polymorphism involving a variable number of tandem repeats (VNTR) has been described in the 3' untranslated region of the gene (SLC6A3) coding for the dopamine transporter (DAT). This polymorphism has 2 common alleles, designated as 10-repeat (*10R) and 9-repeat (*9R), that have been linked with several human clinical phenotypes. Previous(More)
Single photon emission computed tomography (SPECT) studies of regional kinetic uptake and pharmacological specificity of [123I]methyl 3 beta-(4-iodophenyl) tropane-2 beta-carboxylate ([123I]beta-CIT) were performed in nonhuman primates (n = 41). In control experiments, activity was concentrated in striatum and in hypothalamic/midbrain regions. Striatal(More)
Few studies have demonstrated in vivo alterations of human serotonin and dopamine transporters (SERTS and DATS) during antidepressant treatment. The current study measured these transporter availabilities with [(123)I]beta-CIT single photon emission computed tomography (SPECT) during administration of selective serotonin reuptake inhibitors (SSRIs) or a(More)