The fatigability of rat hindlimb muscles after acute irreversible
acetylcholinesterase inhibition.
Panenic, Robert, Victor Gisiger and Phillip F. Gardiner.
1D[acute]epartement de kin[acute]esiologie et and
2D[acute]epartement de pathologie et biologie cellulaire,
Universit[acute]e de Montr[acute]eal, C.P. 6128, Succursale Centre
-ville, Montr[acute]eal, Qu[acute]ebec H3C 3J7, Canada
APStracts 6:0278A, 1999.
The purpose of this study was to investigate the functional impact of
acute irreversible inhibition of acetylcholinesterase (AChE) on the
fatigability of medial gastrocnemius (MG) and plantaris (PL) muscles
of Sprague-Dawley rats. Following a treatment with methanesulfonyl
fluoride (MSF, a lipid-soluble anticholinesterase), which reduced
their AChE activity by more than 90 %, these muscles were subjected
to an in situ indirect stimulation protocol including a series of
isolated twitch and tetanic contractions preceding a 3 minute fatigue
regimen (100-ms trains at 75 Hz applied every 1.5 s). During the
first minute of the fatigue regimen, the effects of AChE inhibition
were already near maximal including marked reductions in peak tension
and the force-time integral (area), as well as a decrement of CMAP
amplitudes within a stimulus train. Neuromuscular transmission (NMT)
failure was the major contributor of the force decreases in the AChE
-inhibited muscles. However, despite this NMT failure, muscles of
which all AChE molecular forms were nearly completely inhibited were
still able to function, although abnormally, during 3 minutes of
intermittent high frequency nerve stimulation.
Received 20 August 1998; accepted in final form 3 June 1999.
APS Manuscript Number A743-8.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 25 June 1999