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The Excitability of Human Corticospinal Neurons is Depressed by Thiopental

Published online by Cambridge University Press:  18 September 2015

K. Kong ,
C. Ukachoke ,
G. McGuire ,
D. Wong  and
P. Ashby
K. Kong
Affiliation:
Division of Neurology and Playfair Neuroscience Unit, University of Toronto, Toronto
C. Ukachoke
Affiliation:
Division of Neurology and Playfair Neuroscience Unit, University of Toronto, Toronto
G. McGuire
Affiliation:
Department of Anaesthesia, University of Toronto, Toronto
D. Wong
Affiliation:
Department of Anaesthesia, University of Toronto, Toronto
P. Ashby*
Affiliation:
Division of Neurology and Playfair Neuroscience Unit, University of Toronto, Toronto
*
Division of Neurology, Playfair Neuroscience Unit #13-319, Toronto Western Hospital, 399 Bathurst Streel, Toronto, Ontario, Canada M5T 2S8
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Abstract

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Background

We tested the effect of thiopental on the excitability of the corticospinal-motoneuron axis in normal human subjects.

Methods

Magnetic stimulation was used to excite the neurons in the motor cortex which give rise to the fast conducting corticospinal pathway. The characteristics of the composite excitatory post-synaptic potentials (EPSPs) produced in individual spinal motoneurons by cortical stimulation were derived from changes in the firing probability of voluntarily activated motor units of the first dorsal interosseous muscle.

Results

In 5 normal subjects, we found that thiopental, in incremental doses sufficient to sustain drowsiness (total dose 75 to 175 mg), significantly reduced the amplitude of these composite EPSPs.

Conclusions

Thiopental reduced the facilitation of motoneurons from the cortex most likely by depressing cortical neurons.

Type
Original Articles
Information
Canadian Journal of Neurological Sciences , Volume 22 , Issue 3 , August 1995 , pp. 218 - 222
Copyright
Copyright © Canadian Neurological Sciences Federation 1995

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