Direct demonstration of the effect of lorazepam on the excitability of the human motor cortex

Clin Neurophysiol. 2000 May;111(5):794-9. doi: 10.1016/s1388-2457(99)00314-4.


Objectives: The present study explored the effects of lorazepam, a benzodiazepine with agonist action at the GABA(A) receptor, on human motor cortex excitability as tested using transcranial magnetic stimulation.

Methods: We recorded directly the descending volley evoked by single and paired transcranial magnetic stimulation from the spinal cord of a conscious subject with a cervical epidural electrode before and after a single oral dose of lorazepam. We evaluated the effects of lorazepam on the descending volleys evoked by a single magnetic stimulation and paired cortical stimulation using the intracortical inhibition paradigm (subthreshold conditioning stimulus) and the short latency intracortical facilitation paradigm (suprathreshold conditioning stimulus).

Results: Using a single magnetic stimulus lorazepam decreased the amplitude of the later I waves in the descending volley; this was accompanied by a decrease in the amplitude of the evoked EMG response. Using the intracortical inhibition paradigm lorazepam increased the amount of corticocortical inhibition, particularly at 4 and 5 ms interstimulus intervals. There was no effect on the amount of facilitation observed in the short latency intracortical facilitation paradigm.

Conclusions: The present findings provide direct evidence that lorazepam increases the excitability of inhibitory circuits in the human motor cortex.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Anti-Anxiety Agents / therapeutic use*
  • Anxiety / drug therapy
  • Electric Stimulation Therapy
  • Electromyography / drug effects
  • Functional Laterality
  • Humans
  • Lorazepam / therapeutic use*
  • Low Back Pain / physiopathology
  • Low Back Pain / therapy
  • Magnetics*
  • Motor Cortex / drug effects*
  • Motor Cortex / physiopathology
  • Reaction Time
  • Receptors, GABA-A / physiology
  • Spinal Cord / drug effects
  • Spinal Cord / physiopathology


  • Anti-Anxiety Agents
  • Receptors, GABA-A
  • Lorazepam