title: Differential effects of anesthetics on in vivo skeletal muscle contractile function in the mouse.
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.
authors.affiliation: Muscle Biology Laboratory, Texas A & M University, College Station 77843-4243, USA.
authors.forename: C P
authors.initials: CP
authors.lastname: Ingalls
authors.forename: G L
authors.initials: GL
authors.lastname: Warren
authors.forename: D A
authors.initials: DA
authors.lastname: Lowe
authors.forename: D B
authors.initials: DB
authors.lastname: Boorstein
authors.forename: R B
authors.initials: RB
authors.lastname: Armstrong
mesh_terms: D000758:Anesthesia; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001835:Body Weight / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D051381:Rats
chemical_list: D000777:Anesthetics