Model 300c lr

In vivo maximal isometric torque of the ankle plantarflexors (gastrocnemius, soleus, and plantaris muscle) was assessed as previously described [23 (link)–25 (link)] and was determined at the terminal time point. Briefly, mice were anesthetized using 2% isoflurane in oxygen, and then the left hindlimb was depilated and aseptically prepared, the foot placed in a foot-plate attached to a servomotor (Model 300C-LR; Aurora Scientific, Aurora, Ontario, Canada), and Pt-Ir needle electrodes (Grass Technologies, West Warwick, RI, USA) were inserted percutaneously on either side of the nerve. To avoid recruitment of the anterior crural muscles responsible for dorsiflexion, the common perineal nerve was severed [26 (link)]. Peak isometric torque was achieved by varying the current delivered to the sciatic nerve which branches to the tibial nerve thus innervating the ankle plantarflexor muscles. To account for differences in body size among mice, torques (mN●m) was normalized by body mass (kg).

Prior to assessment of in vivo peak isometric torque of the ankle plantarflexors, mice were anaesthetized using 1.5% isoflurane at an oxygen flow rate of 0.4 L/min. The left hindlimb was depilated and aseptically prepared and the foot placed in a foot-plate attached to a servomotor (Model 300C-LR; Aurora Scientific, Aurora, Ontario, Canada). The left peroneal nerve was severed and platinum-iridium needle electrodes (Model E2–12; Grass Technologies, West Warwick, RI) were placed on either side of the sciatic nerve to elicit isolated contraction of the plantarflexor muscles. Peak isometric torque was defined as the greatest torque measured during a 200-ms stimulation using 1-ms square-wave pulses at 300 Hz and increasing amperage 0.6 to 2.0 mA (models S48 and SIU5; Grass Technologies). Fatigability of the plantarflexors muscles was assessed using 120 submaximal isometric contractions were performed in 2 min using 330 ms stimulations at 50 Hz.

The peak isometric torque (N•mm) of the ankle plantarflexors was assessed as previously described^{66 ,67} . Briefly, the foot of anesthetized mice was placed on a footplate attached to a servomotor (model 300C-LR; Aurora Scientific). Two Pt-Ir electrode needles (Aurora Scientific) were inserted percutaneously over the tibial nerve, just posterior/posterior-medial to the knee. The ankle joint was secured at a 90° angle. The peak isometric torque was achieved by varying the current delivered to the nerve at a frequency of 100 Hz, 0.1-ms square wave pulse, 500 ms stimulation duration. Force frequency data was recorded by stimulating using frequencies ranging from 1 to 150 Hz with 30 s recovery between each measurement. For relative force measurements, force of the same animal was measured before and after treatment, and the percent change was calculated. Force measurement acquisition was blinded where researchers were unaware of the genotype or treatment conditions. Data were collected with the Aurora Scientific Dynamic Muscle Data Acquisition and Analysis Software.

In vivo peak isometric torque of the ankle plantarflexors was assessed as previously described [26 (link)]. Briefly, anesthesia was induced using an induction chamber and 5% isoflurane in oxygen. Anesthesia was maintained using 1.5% isoflurane at an oxygen flow rate of 0.4L/min. The left hindlimb was depilated and aseptically prepared and the foot placed in a foot-plate attached to a servomotor (Model 300C-LR; Aurora Scientific, Aurora, Ontario, Canada). The left peroneal nerve was severed and platinum-iridium needle electrodes (Model E2-12; Grass Technologies, West Warwick, RI) were placed on either side of the sciatic nerve to elicit contraction of the plantarflexor muscles [27 (link)]. Peak isometric torque was defined as the greatest torque measured during a 200-ms stimulation using 1-ms square-wave pulses at 300 Hz and increasing amperage 0.6 to 2.0 mA (models S48 and SIU5; Grass Technologies). Fatigability of the plantarflexor muscles was assessed using a protocol that has been shown to induce ~50% torque loss over the course of 120 contractions by using physiological stimulation frequencies of the hind limb, which range from 45–60 Hz [28 (link), 29 (link)]. Briefly, for this study, the mice performed 120 submaximal isometric contractions for 2 min using 330 ms stimulations at 50 Hz.