Differential effects of anesthetics on in vivo skeletal muscle
contractile function in the mouse.
Ingalls, Christopher P., Gordon L. Warren, Dawn A. Lowe, and R. B.
Armstrong.
Muscle Biology Laboratory, Texas A&M University, College
Station, Texas 77843-4243
APStracts 2:0336A, 1995.
The purpose of this study was to evaluate the effects of four
anesthetic regimens on in vivo contractile function of mouse ankle
dorsiflexor muscles. The torque-frequency and torque-velocity
relationships were determined for the following anesthetics:
fentanyl-droperidol and diazepam (F-d/d); ketamine and xylazine
(K/x); pentobarbital sodium (Ps); and methoxyflurane (Mf). Mf, Ps and
F-d/d regimens resulted in comparable contractile responses at low
doses, whereas K/x produced a relative depression in isometric
contractile function as shown by a decrease (-13.9%; p<0.05) in
the torque-time-integral at the 300 Hz stimulation frequency.
Moreover, K/x caused a shift to the left in the torque-frequency
curve as indicated by increases in torque-time integrals at 25 and 50
Hz. Both Ps and F-d/d regimens exhibited dose-dependent effects
during the isovelocity contractions. Ps significantly reduced work (
-28.7%) and average power (-28.9%) at 800 degrees /s at the high dose.
In contrast, F-d/d anesthesia resulted in increases in peak torque
(16%-20%) and work (15%-18%) output at all eccentric contraction
velocities at the high dose, whereas average power was increased only
at -800 degrees /s (17%) and -1000 degrees /s (17%). In conclusion,
commonly used anesthetic regimens can affect the contractile response
in vivo; K/x and Ps yield smaller torque output whereas Mf and F-d/d
consistently produce larger contractile responses. Mf and F-d/d are
recommended for use in studying skeletal muscle function in mice in
vivo.
Received 26 January 1995; accepted in final form 14 July 1995.
APS Manuscript Number A98-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 August 1995.