title: Transcranial direct-current stimulation increases extracellular dopamine levels in the rat striatum.
abstract: BACKGROUND
  Transcranial direct-current stimulation (tDCS) is a non-invasive procedure that achieves polarity-dependent modulation of neuronal membrane potentials. It has recently been used as a functional intervention technique for the treatment of psychiatric and neurological diseases; however, its neuronal mechanisms have not been fully investigated in vivo.
  
  
  OBJECTIVE
  To investigate whether the application of cathodal or anodal tDCS affects extracellular dopamine and serotonin levels in the rat striatum.
  
  
  METHODS
  Stimulation and in vivo microdialysis were carried out under urethane anesthesia, and microdialysis probes were slowly inserted into the striatum. After the collection of baseline fractions in the rat striatum, cathodal or anodal tDCS was applied continuously for 10 min with a current intensity of 800 μA from an electrode placed on the skin of the scalp. Dialysis samples were collected every 10 min until at least 400 min after the onset of stimulation.
  
  
  RESULTS
  Following the application of cathodal, but not anodal, tDCS for 10 min, extracellular dopamine levels increased for more than 400 min in the striatum. There were no significant changes in extracellular serotonin levels.
  
  
  CONCLUSIONS
  These findings suggest that tDCS has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia.
authors.affiliation: Department of Functional Brain Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry Tokyo, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Tanaka
authors.forename: Yuji
authors.initials: Y
authors.lastname: Takano
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanaka
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Hironaka
authors.forename: Kazuto
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Hanakawa
authors.forename: Katsumi
authors.initials: K
authors.lastname: Watanabe
authors.forename: Manabu
authors.initials: M
authors.lastname: Honda
keywords: Parkinson disease; basal ganglia; dopamine; striatum; transcranial direct current stimulation