Tetanus toxin preserves skeletal muscle contractile force and size during limb immobilization

We examined the possibility that tetanus toxin can prevent muscle atrophy associated with limb immobility in rats.

While the knee and ankle joints were immobilized unilaterally, the tibialis anterior (TA) muscle on the immobilized side was injected with 1 μl saline or with 1 ng tetanus toxin. After 2 weeks, TA wet weights, contractile forces, and myofiber sizes from the immobilized sides were compared with those from body weight-matched normal animals.

Saline group wet weights decreased and produced less absolute twitch and tetanic force and normalized tetanic force compared with the toxin or normal groups. Cross-sectional areas of saline group type I, IIa, and IId myofibers, and the masses of saline group IIa, IId, IIb, and toxin group IIb myofibers, were smaller compared with the normal group.

Tetanus toxin prevented common signs of muscle atrophy and may become a useful adjunct to current rehabilitation strategies.