Stroke Unit, Dipartimento di Neuroscienze, Università di Roma Tor Vergata, Rome, Italy.
Clin Neurophysiol. 2011 Apr;122(4):703-7. doi: 10.1016/j.clinph.2010.10.033. Epub 2010 Nov 13.
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.
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.
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.
Dopamine modulation of LTD-like plasticity is impaired when tested in AD patients.
These findings provide evidence of possible dysfunction of dopaminergic transmission in AD patients.
在阿尔茨海默病（AD）的实验模型中，突触可塑性的机制（如长时程抑制（LTD））发生改变。AD 患者中尚未完全研究 LTD 样可塑性机制。
在这里，我们研究了低频（1 Hz）重复经颅磁刺激（rTMS）对一组可能患有 AD 的患者的初级运动皮层的影响，与年龄匹配的健康对照组（HS）进行比较。此外，我们测试了单次口服给予左旋多巴（调节突触可塑性机制的关键神经递质之一）对 rTMS 诱导的可塑性的影响。
我们发现，在 AD 患者中，1 Hz rTMS 方案并未引起预期的抑制作用，而 HS 中则观察到 MEP 的持久抑制。此外，L-多巴在 HS 中诱导了一种明显的可塑性方向逆转形式，而在 AD 中则不明显。
在 AD 患者中测试时，多巴胺对 LTD 样可塑性的调节受损。
这些发现为 AD 患者中多巴胺能传递的可能功能障碍提供了证据。
