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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Adult, Amygdala, Benzylamines, Binding, Competitive, Carbon Radioisotopes, Female, Gene Frequency, Genotype, Heterozygote, Homozygote, Humans, Male, Mesencephalon, Middle Aged, Neural Pathways, Positron-Emission Tomography, Serotonin, Serotonin Plasma Membrane Transport Proteins, Thalamus.
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Is midbrain serotonin transporter binding potential measured with [ 11C ] DASB affected by serotonin transporter genotype? Context: Homozygote carriers of two long (L) alleles of the serotonin transporter (5-HTT) regulatory region displayed in vitro a twofold increase in 5-HTT expression compared with carriers of one or two short (S) alleles. However, in vivo imaging studies yielded contradictory results. Recently, an A > G exchange leading to differential transcriptional activation of 5-HTT mRNA in lymphobalstoid cell lines was discovered in the 5-HTT regulatory region. In vitro and in vivo evidence suggests that [(11)C]DASB, a new 5-HTT ligand offers some advantages over the ligands used in previous studies in measuring 5-HTT density independent of synaptic levels of serotonin. We assessed 5-HTT binding potential (BP (2)) in the midbrain of 19 healthy subjects with positron emission tomography and [(11)C]DASB. Accounting for the hypothesized functional similarity of L (G) and S in driving 5-HTT transcription, we assessed whether L (A) L (A) homozygotes display increased midbrain BP (2) compared with carriers of at least one S allele. BP (2) in the midbrain was significantly increased in L (A) L (A) homozygotes compared with carriers of at least one S allele. Interestingly, the genotype effect on the midbrain was significantly different from that on the thalamus and the amygdala where no group differences were detected.
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This in vivo study provides further evidence that subjects homozygous for the L (A) allele display increased expression of 5-HTT in the midbrain, the origin of central serotonergic projections. Final Decision: yes