101.5  Thursday, Jan. 7  Self-ReInnervation of the Lateral Gastrocnemius in Guineafowl CARR, J.A.*; BIEWENER, A.A.; Harvard University; Harvard University carr@fas.harvard.edu

Running and walking requires that animals be able to negotiate variable terrain and recover from unexpected perturbations. Reflex responses that monitor and respond to changes in muscle force and length play an important role in controlling how an animal stabilizes its center of mass and produces ground reaction forces during locomotion.

One method of studying the role of muscle reflexes during locomotion is to eliminate reflex responses by performing surgical self-reinnervation. Self-reinnervation experiments have demonstrated that motor innervation can be restored, but not sensory afferents. The goal of this study was to determine whether self-reinnervation in the Lateral Gastrocnemius (LG) in guineafowl caused the loss and subsequent reestablishment of motor innervation and the permanent loss of sensory afferents. Muscle function was monitored during locomotion by measuring joint kinematics, muscle electrical activity, and the presence or absence of a calcaneal reflex. Measurements were performed at three times: prior to denervation surgery, then at three and six weeks post surgery. By demonstrating a loss of function followed by the recovery of motor function we will validate a bipedal model that allows us to study the role of reflexes during legged locomotion.

At three weeks post surgery we demonstrated a loss of function in the LG. The denervation of this muscle affected joint kinematics at both the ankle and TMP joints. There was a significant increase in the amount of ankle flexion that occurred during running. There was also a significant increase in both flexion and extension at the TMP joint. At six weeks post surgery we demonstrated successful reinnervation of the LG by measuring muscle activity during locomotion. Also at six weeks post surgery we demonstrated the lack of a sensory reflex in the LG by the inability to elicit calcaneal tendon reflex.