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Updated: Jul 20, 2026
Single Cell Measurement of Dopamine Release with Simultaneous Voltage-clamp and Amperometry
Published on: November 21, 2012
Dual modulating effects of amphetamine on neuronal excitability and stimulation-induced plasticity in human motor
Ulf Ziemann1, Alda Tam, Cathrin Bütefisch
1Human Cortical Physiology Section, NINDS, National Institutes of Health, Building 10, Bethesda, MD 20892, USA. u.ziemann@em.uni-frankfurt.de
Objectives:
The objective of the present study is to test the modulating effects of dextro-amphetamine (d-AMP) on excitability and stimulation-induced plasticity in human motor cortex.
Methods:
Transcranial magnetic stimulation (TMS) was used to measure motor threshold, motor evoked potential (MEP) size and paired-pulse intracortical facilitation (ICF) in the biceps muscle of 7 healthy subjects before and after two different experimental manipulations: temporary forearm ischemic nerve block (INB) alone, or INB plus 0.1 Hz repetitive TMS (INB+rTMS) of the motor cortex contralateral to INB. Both manipulations were run after treatment with 10mg of d-AMP or placebo (PBO).
Results:
In the PBO experiments, INB alone had no significant effect on MEP size or ICF, while INB+rTMS produced long-lasting (>60 min) increases. Compared with PBO, d-AMP led to a short-lasting ( approximately 10 min) increase in MEP size in the INB alone experiment, but suppressed the long-lasting increases of MEP size and ICF in the INB+rTMS experiment.
Conclusions:
The present findings suggest that d-AMP increases neuronal excitability but suppresses long-lasting stimulation-induced plasticity in human motor cortex. These dual effects may be relevant when using d-AMP to modulate human cortex function.
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