Effects of phenytoin on cortical excitability in humans.
We studied the effects of a loading dose of phenytoin on motor cortex excitability in five healthy volunteers. Phenytoin elevated motor thresholds to transcranial magnetic stimulation (TMS) in all subjects, but had no effects on motor-evoked potential amplitudes, silent period durations, and intracortical excitability tested by paired TMS during rest and voluntary muscle activation. These results are consistent with the hypothesis that blockade of voltage-gated sodium channels decreases membrane excitability and elevates the threshold to TMS, but will not reduce intracortical excitability.
Chen
R
R
Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA.
Samii
A
A
Caños
M
M
Wassermann
E M
EM
Hallett
M
M
D000328:Adult; D002540:Cerebral Cortex / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D009044:Motor Cortex / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D010672:Phenytoin / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects
D015222:Sodium Channels; D010672:Phenytoin