ABSTRACT
<p><b>OBJECTIVE</b>To compare the effect of botulinum neurotoxin A (BTA) and denervation in inducing masseter muscle atrophy in rabbits to provide experimental evidence for the safe clinical application of BTA.</p><p><b>METHODS</b>Seventy-five healthy adult New Zealand white rabbits were randomized equally into denervation group, BTA group and normal control group. In the former two groups, the rabbits were subjected to right masseter muscle denervation and botulinum (3 µg/kg) injection at the muscle, respectively, with the left side as the control. The thickness of the denervated masseter was determined using B type ultrasound and its weight measured after the treatment.</p><p><b>RESULTS</b>The thickness of the masseter muscle on the experimental side was significantly decreased to 50.80% and 54.07%, and its weight to 66.80% and 56.16% of the normal level after denervation and BTA injection, respectively.</p><p><b>CONCLUSION</b>BTA-induced denervation produces less potent atrophy-inducing effect on skeletal muscle than surgical denervation. BTA causes atrophy mainly at the injection site of the target muscle without significant diffusion or toxicity to the muscular cells.</p>