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Clin Neurophysiol. 2000 May;111(5):794-9.

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

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  • 1Istituto di Neurologia, Universit√† Cattolica, L.go A. Gemelli 8, 00168, Rome, Italy. dilazzar@rm.ats.it

Abstract

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.

PMID:
10802448
[PubMed - indexed for MEDLINE]
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