PLoS ONE (Jan 2017)

Repeated dexamphetamine treatment alters the dopaminergic system and increases the phMRI response to methylphenidate.

  • Anouk Schrantee,
  • Jordi L Tremoleda,
  • Marzena Wylezinska-Arridge,
  • Valentine Bouet,
  • Peter Hesseling,
  • Gideon F Meerhoff,
  • Kora M de Bruin,
  • Jan Koeleman,
  • Thomas Freret,
  • Michel Boulouard,
  • Emilie Desfosses,
  • Laurent Galineau,
  • Alessandro Gozzi,
  • François Dauphin,
  • Willy Gsell,
  • Jan Booij,
  • Paul J Lucassen,
  • Liesbeth Reneman

DOI
https://doi.org/10.1371/journal.pone.0172776
Journal volume & issue
Vol. 12, no. 2
p. e0172776

Abstract

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Dexamphetamine (AMPH) is a psychostimulant drug that is used both recreationally and as medication for attention deficit hyperactivity disorder. Preclinical studies have demonstrated that repeated exposure to AMPH can induce damage to nerve terminals of dopamine (DA) neurons. We here assessed the underlying neurobiological changes in the DA system following repeated AMPH exposure and pre-treated rats with AMPH or saline (4 times 5 mg/kg s.c., 2 hours apart), followed by a 1-week washout period. We then used pharmacological MRI (phMRI) with a methylphenidate (MPH) challenge, as a sensitive and non-invasive in-vivo measure of DAergic function. We subsequently validated the DA-ergic changes post-mortem, using a.o. high-performance liquid chromatography (HPLC) and autoradiography. In the AMPH pre-treated group, we observed a significantly larger BOLD response to the MPH challenge, particularly in DA-ergic brain areas and their downstream projections. Subsequent autoradiography studies showed that AMPH pre-treatment significantly reduced DA transporter (DAT) density in the caudate-putamen (CPu) and nucleus accumbens, whereas HPLC analysis revealed increases in the DA metabolite homovanillic acid in the CPu. Our results suggest that AMPH pre-treatment alters DAergic responsivity, a change that can be detected with phMRI in rats. These phMRI changes likely reflect increased DA release together with reduced DAT binding. The ability to assess subtle synaptic changes using phMRI is promising for both preclinical studies of drug discovery, and for clinical studies where phMRI can be a useful tool to non-invasively investigate DA abnormalities, e.g. in neuropsychiatric disorders.