title: Allelic variation in the serotonin transporter promoter modulates cortical excitability.
abstract: BACKGROUND
  Transcranial magnetic stimulation (TMS) is a noninvasive procedure that may be used to study individual differences in motor cortex excitability. Such differences are assumed to reflect serotonergic and other inputs to the motor cortex.
  
  
  METHODS
  Here we investigate the impact of a functional polymorphism in the promoter region of the 5-hydroxytryptamine transporter gene (5-HTTLPR) on measures of motor cortex excitability.
  
  
  RESULTS
  Sixty healthy subjects carrying one or two copies of the short 5-HTTLPR allele (s/s and s/l) showed a significant reduction in short intracortical inhibition (SICI, p = .012) and an increased cortical silent period (p = .042) compared with 60 age- and sex-matched individuals homozygous for the long allele (l/l). In contrast, motor threshold and intracortical facilitation did not differ significantly between groups.
  
  
  CONCLUSIONS
  These results provide further evidence of a role for serotonergic transmission in the modulation of cortical excitability. Differential effects on the measures under study suggest a pattern of prioritization in bioamine regulation of cortical inhibition.
authors.affiliation: Department of Psychiatry, University of Regensburg, Universitaetsstrasse 84, Regensburg D-93053, Germany. Berthold.Langguth@medbo.de
authors.forename: Berthold
authors.initials: B
authors.lastname: Langguth
authors.forename: Philipp
authors.initials: P
authors.lastname: Sand
authors.forename: Roger
authors.initials: R
authors.lastname: Marek
authors.forename: Michael
authors.initials: M
authors.lastname: Landgrebe
authors.forename: Elmar
authors.initials: E
authors.lastname: Frank
authors.forename: Göran
authors.initials: G
authors.lastname: Hajak
authors.forename: Peter
authors.initials: P
authors.lastname: Eichhammer
mesh_terms: D000328:Adult; D000483:Alleles; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000502:physiology*; D013181:Cortical Spreading Depression / Q000235:genetics*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000235:genetics*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D014644:Genetic Variation; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D050486:Serotonin Plasma Membrane Transport Proteins