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Updated: Aug 24, 2026
Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation
Published on: February 23, 2020
Enhanced brain motor activity in patients with MS after a single dose of 3,4-diaminopyridine
C Mainero1, M Inghilleri, P Pantano
1Section of Clinical Neurology, Department of Neurological Sciences, University of Rome La Sapienza, Italy. caterina.mainero@uniroma1.it
Background:
3,4-diaminopyridine (3,4-DAP), a potassium (K+) channel blocker, improves fatigue and motor function in multiple sclerosis (MS). Although it was thought to do so by restoring conduction to demyelinated axons, recent experimental data show that aminopyridines administered at clinical doses potentiate synaptic transmission.
Objective:
To investigate motor cerebral activity with fMRI and transcranial magnetic stimulation (TMS) after a single oral dose of 3,4-DAP in patients with MS.
Methods:
Twelve right-handed women (mean +/- SD age 40.9 +/- 9.3 years) underwent fMRI on two separate occasions (under 3,4-DAP and under placebo) during a simple motor task with the right hand. FMRI data were analyzed with SPM99. After fMRI, patients underwent single-pulse TMS to test motor threshold, amplitude, and latency of motor evoked potentials, central conduction time, and the cortical silent period; paired-pulse TMS to investigate intracortical inhibition (ICI) and intracortical facilitation (ICF); and quantitative electromyography during maximal voluntary contraction.
Results:
FMRI motor-evoked brain activation was greater under 3,4-DAP than under placebo in the ipsilateral sensorimotor cortex and supplementary motor area (p < 0.05). 3,4-DAP decreased ICI and increased ICF; central motor conduction time and muscular fatigability did not change.
Conclusion:
3,4-DAP may modulate brain motor activity in patients with MS, probably by enhancing excitatory synaptic transmission.
Insights
3,4-diaminopyridine (3,4-DAP) enhances motor brain activity in multiple sclerosis (MS) patients by boosting synaptic transmission. This potassium channel blocker improved motor function and cerebral activation, suggesting a new therapeutic mechanism for MS.
Area of Science:
- Neuroscience
- Neuropharmacology
- Clinical Neurology
Background:
- 3,4-diaminopyridine (3,4-DAP) is a potassium channel blocker known to improve fatigue and motor function in multiple sclerosis (MS).
- While previously thought to restore conduction in demyelinated axons, recent evidence suggests aminopyridines may potentiate synaptic transmission at clinical doses.
Purpose of the Study:
- To investigate the effects of a single oral dose of 3,4-DAP on motor cerebral activity in MS patients.
- Utilized functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) to assess brain activity and motor pathways.
Main Methods:
- Twelve female MS patients underwent fMRI during a motor task, with and without 3,4-DAP.
- Post-fMRI, patients received single-pulse and paired-pulse TMS to evaluate motor evoked potentials, central conduction time, intracortical inhibition (ICI), and intracortical facilitation (ICF).
- Quantitative electromyography was used to assess maximal voluntary contraction.
Main Results:
- 3,4-DAP significantly increased fMRI motor-evoked brain activation in the ipsilateral sensorimotor cortex and supplementary motor area compared to placebo.
- The drug reduced ICI and increased ICF, indicating modulation of intracortical excitability.
- No significant changes were observed in central motor conduction time or muscular fatigability.
Conclusions:
- 3,4-DAP appears to modulate brain motor activity in MS patients.
- The findings suggest that 3,4-DAP's therapeutic effects may be mediated by enhanced excitatory synaptic transmission.
- This study provides novel insights into the neurophysiological mechanisms underlying 3,4-DAP's benefits in MS.
