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Published on: March 23, 2011
Altered dopamine modulation of LTD-like plasticity in Alzheimer's disease patients
Giacomo Koch1, Zaira Esposito, Claudia Codecà
1Stroke Unit, Dipartimento di Neuroscienze, Università di Roma Tor Vergata, Rome, Italy. g.koch@hsantalucia.it
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.
Significance:
These findings provide evidence of possible dysfunction of dopaminergic transmission in AD patients.
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