Skeletal muscle disuse results in a decrease in the volume of myofibers, with a resultant decrease in muscle force production. As the action of tetanus toxin results in increased muscle activity, this animal study was designed to determine the ability of tetanus toxin to prevent changes associated with disuse atrophy.
METHODSFemale Sprague rats were divided into three groups, with all undergoing immobilization. Within the experimental groups, one group underwent tetanus toxin injection and one group underwent saline injection. A third group, receiving no injections, served as controls. Two weeks after the injections, the contractile force, muscle and myofiber morphology, as well as the tibialis anterior weight were analyzed and compared to those of the control group.
RESULTSAfter immobilization, the wet weight of the saline group muscles decreased significantly, to 68% of the wet weight of the control muscles. The wet weight of the toxin-treated muscles maintained 98% of the wet weight of the control muscles. The maximal tetanic tension (Po) of the toxin injected muscles did not differ from that of the control muscles. The saline group muscles developed on average only 58%/44% of the maximal twitch response (Pt)/ maximal tetanic tension (Po) produced by control muscles. Saline group muscles developed on average only 61%/45% of the Pt/ Po generated by the toxin injected muscles.
CONCLUSIONThis animal study found that tetanus toxin can prevent common signs of muscle disuse atrophy.