title: Altered dopamine modulation of LTD-like plasticity in Alzheimer's disease patients.
abstract: OBJECTIVE
  Mechanisms of synaptic plasticity like long term depression (LTD) are altered in experimental models of Alzheimer's disease (AD). LTD-like plasticity mechanisms has not been yet fully investigated in AD patients.
  
  
  METHODS
  Here we studied the effects of low frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex in a group of patients with a diagnosis of probable AD, compared to healthy age-matched controls (HS). Moreover, we tested the effects of a single dose of orally administered L-dopa, one of the key neurotransmitters in modulating synaptic plasticity mechanisms, on rTMS induced plasticity.
  
  
  RESULTS
  We found that in AD patients the 1 Hz rTMS protocol did not induce the expected inhibitory effect, while a long lasting inhibition of MEP was observed in HS. In addition, L-dopa induced a clear form of reversal of the direction of plasticity in HS that was not evident in AD.
  
  
  CONCLUSIONS
  Dopamine modulation of LTD-like plasticity is impaired when tested in AD patients.
  
  
  CONCLUSIONS
  These findings provide evidence of possible dysfunction of dopaminergic transmission in AD patients.
authors.affiliation: Stroke Unit, Dipartimento di Neuroscienze, Università di Roma Tor Vergata, Rome, Italy. g.koch@hsantalucia.it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
authors.forename: Zaira
authors.initials: Z
authors.lastname: Esposito
authors.forename: Claudia
authors.initials: C
authors.lastname: Codecà
authors.forename: Francesco
authors.initials: F
authors.lastname: Mori
authors.forename: Hajime
authors.initials: H
authors.lastname: Kusayanagi
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Monteleone
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Lorenzo
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bernardi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Martorana
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000503:physiopathology* / Q000523:psychology; D002540:Cerebral Cortex / Q000503:physiopathology; D003627:Data Interpretation, Statistical; D004298:Dopamine / Q000502:physiology*; D015259:Dopamine Agents / Q000494:pharmacology; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D007980:Levodopa / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D009483:Neuropsychological Tests; D013569:Synapses / Q000502:physiology; D050781:Transcranial Magnetic Stimulation
chemical_list: D015259:Dopamine Agents; D007980:Levodopa; D004298:Dopamine