The variable number of tandem repeats polymorphism of the dopamine transporter gene is not associated with significant change in dopamine transporter phenotype in humans

A 40 base polymorphism of 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). Despite bring located in tire untranslated region of the gene, this polymorphism has been associated with clinical phenotypes associated with dysregulation of dopamine transmission, such as attention deficit hyperactivity disorder and cocaine-induced paranoia. To examine the neurochemical phenotype associated with this polymorphism, we compared amphetamine-induced dopamine release (measured ns displacement of the radiotracer [I-123]IBZMI and DAT expression (measured with [I-123]beta -CIT) in the striatum with Single Photon Computerized Emission Tomography (SPECT). Our sample included 59 subjects, 31 healthy controls and 29 patients with schizophrenia. No significant association was found between VNTR polymorphism and amphetamine-induced dopamine release or DAT density in the total sample, nor when each diagnostic group tons considered separately. Thus, we dill trot replicate the findings of two previous studies, which had suggested that the 9 repeat allele was associated with either an increased or decreased DAT expression, albeit in different patient populations. (C) American College of Neuropsychopharmacology. Published by Elsevier Science Inc.