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Differential effects of anesthetics on in vivo skeletal muscle contractile function in the mouse
C P Ingalls1, G L Warren, D A Lowe
1Muscle Biology Laboratory, Texas A & M University, College Station 77843-4243, USA.
Abstract:
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 in the torque-time integral at the 300-Hz stimulation frequency (-13.9%; P < 0.05). 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 (17%) and -1,000 degrees/s (17%). In conclusion, commonly used anesthetic regimens can affect the contractile response in vivo; K/x and Ps yield smaller torque outputs, 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.
Insights
Methoxyflurane (Mf) and fentanyl-droperidol/diazepam (F-d/d) anesthesia are recommended for studying mouse skeletal muscle function in vivo, as they produced larger contractile responses compared to ketamine/xylazine (K/x) and pentobarbital sodium (Ps).
Area of Science:
- Physiology
- Anesthesiology
- Pharmacology
Background:
- Anesthetic choice significantly impacts physiological measurements.
- Understanding anesthetic effects on skeletal muscle contractile function is crucial for accurate in vivo research.
- Previous studies have not comprehensively evaluated common anesthetic regimens on mouse muscle performance.
Purpose of the Study:
- To evaluate the in vivo effects of four anesthetic regimens on mouse ankle dorsiflexor muscle contractile function.
- To determine the impact of fentanyl-droperidol/diazepam (F-d/d), ketamine/xylazine (K/x), pentobarbital sodium (Ps), and methoxyflurane (Mf) on torque-frequency and torque-velocity relationships.
Main Methods:
- In vivo contractile function of mouse ankle dorsiflexor muscles was assessed.
- Torque-frequency and torque-velocity relationships were determined under four different anesthetic regimens.
- Dose-dependent effects of pentobarbital sodium and fentanyl-droperidol/diazepam were analyzed during isovelocity contractions.
Main Results:
- Ketamine/xylazine (K/x) significantly depressed isometric contractile function and shifted the torque-frequency curve leftward.
- Pentobarbital sodium (Ps) at high doses reduced work and average power during isovelocity contractions.
- Methoxyflurane (Mf) and fentanyl-droperidol/diazepam (F-d/d) regimens produced comparable contractile responses at low doses and larger outputs at high doses, with F-d/d increasing peak torque and work across eccentric velocities.
Conclusions:
- Commonly used anesthetic regimens can alter in vivo skeletal muscle contractile responses.
- Ketamine/xylazine (K/x) and pentobarbital sodium (Ps) result in diminished torque outputs.
- Methoxyflurane (Mf) and fentanyl-droperidol/diazepam (F-d/d) are recommended for studying mouse skeletal muscle function due to their consistent and favorable contractile responses.