title: D2 receptor genotype and striatal dopamine signaling predict motor cortical activity and behavior in humans.
abstract: OBJECTIVE
  Pre-synaptic D2 receptors regulate striatal dopamine release and DAT activity, key factors for modulation of motor pathways. A functional SNP of DRD2 (rs1076560 G>T) is associated with alternative splicing such that the relative expression of D2S (mainly pre-synaptic) vs. D2L (mainly post-synaptic) receptor isoforms is decreased in subjects with the T allele with a putative increase of striatal dopamine levels. To evaluate how DRD2 genotype and striatal dopamine signaling predict motor cortical activity and behavior in humans, we have investigated the association of rs1076560 with BOLD fMRI activity during a motor task. To further evaluate the relationship of this circuitry with dopamine signaling, we also explored the correlation between genotype based differences in motor brain activity and pre-synaptic striatal DAT binding measured with [(123)I] FP-CIT SPECT.
  
  
  METHODS
  Fifty healthy subjects, genotyped for DRD2 rs1076560 were studied with BOLD-fMRI at 3T while performing a visually paced motor task with their right hand; eleven of these subjects also underwent [(123)I]FP-CIT SPECT. SPM5 random-effects models were used for statistical analyses.
  
  
  RESULTS
  Subjects carrying the T allele had greater BOLD responses in left basal ganglia, thalamus, supplementary motor area, and primary motor cortex, whose activity was also negatively correlated with reaction time at the task. Moreover, left striatal DAT binding and activity of left supplementary motor area were negatively correlated.
  
  
  CONCLUSIONS
  The present results suggest that DRD2 genetic variation was associated with focusing of responses in the whole motor network, in which activity of predictable nodes was correlated with reaction time and with striatal pre-synaptic dopamine signaling. Our results in humans may help shed light on genetic risk for neurobiological mechanisms involved in the pathophysiology of disorders with dysregulation of striatal dopamine like Parkinson's disease.
authors.affiliation: Department of Neurological and Psychiatric Sciences, University of Bari Aldo Moro, Bari, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Fazio
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Blasi
authors.forename: Paolo
authors.initials: P
authors.lastname: Taurisano
authors.forename: Apostolos
authors.initials: A
authors.lastname: Papazacharias
authors.forename: Raffaella
authors.initials: R
authors.lastname: Romano
authors.forename: Barbara
authors.initials: B
authors.lastname: Gelao
authors.forename: Gianluca
authors.initials: G
authors.lastname: Ursini
authors.forename: Tiziana
authors.initials: T
authors.lastname: Quarto
authors.forename: Luciana
authors.initials: L
authors.lastname: Lo Bianco
authors.forename: Annabella
authors.initials: A
authors.lastname: Di Giorgio
authors.forename: Marina
authors.initials: M
authors.lastname: Mancini
authors.forename: Teresa
authors.initials: T
authors.lastname: Popolizio
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rubini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bertolino
mesh_terms: D001931:Brain Mapping; D003342:Corpus Striatum / Q000502:physiology; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D005838:Genotype; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity / Q000235:genetics*; D009044:Motor Cortex / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide; D011930:Reaction Time; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult
chemical_list: D017448:Receptors, Dopamine D2; D004298:Dopamine