This article outlines a surgical procedure for isolating the gastrocnemius and tibialis anterior muscles from a euthanized mouse. The method includes detailed steps for muscle identification, excision, and preservation for further analysis.
To begin, prep a euthanized mouse in the supine position. Clamp one of its feet to extend the limb vertically. Gently hold the skin of the lower limb.
Next, surgically remove the skin and fascia, the layer of loose connective tissue just underneath the skin, exposing the underlying muscle bellies of the lower limb.
Identify the gastrocnemius muscle - a large, superficial two-headed muscle - on the posterior lower limb. It originates from the lateral and medial condyles of the posterior femur and attaches to the calcaneus - heel bone - via the calcaneal tendon.
Hold the distal end of the muscle and pull the muscle belly towards its origin. Excise the gastrocnemius calcaneal tendon followed by the muscle at the origin closest to the femur.
Now, locate the tibialis anterior muscle. The muscle originates from the anterolateral surface of the tibia and attaches to the medial cuneiform bone via the distal tendon.
Detach the tibialis muscle belly from the underlying connective tissue. Cut the distal tendon and the muscle at the origin closest to the tibia.
Finally, transfer the excised muscles into cryotubes. Store the tubes at low temperatures until further downstream analysis.
To avoid fur contamination, spray 70% ethanol over the entire body. Then, place the animal on a dissection bed in the supine position and attach one hind limb to an elevated buret clamp to extend the limb vertically. Using Dumont forceps, grasp the superficial skin of the hind limb, and use curved fine scissors to gently remove the skin and fascia, exposing the underlying muscle bellies of the lower limb.
Identify the gastrocnemius muscle on the posterior lower limb by its origin at the lateral and medial condyles on the posterior femur and its insertion at the calcaneus via the calcaneal tendon. Use the forceps to grasp the distal end of the gastrocnemius and pull the muscle belly toward its origin. Then, use scissors to cut the muscle at the origin as close as possible to the femur and transfer the muscle to a pre-weighed dish.
Weigh the dish immediately and transfer the muscle into a pre-labeled cryotube. Next, identify the tibialis anterior muscle from its origin at the anterolateral surface of the tibia and its insertion at the medial cuneiform via its distal tendon. Then, grasp the foot by the digits with the index finger and thumb and insert the tip of the Dumont forceps immediately under the superficial distal tendon of the tibialis.
Move the forceps such that the blunt side can be used to detach the tibialis muscle belly from the underlying connective tissue and use the fine curved scissors to cut the distal tendon. Then, cut the muscle at the origin as close as possible to the tibia.
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