J Korean Ophthalmol Soc.  1997 Dec;38(12):2214-2222.

Botulinum Toxin Induced Morphological Changes in the Rabbit Extraocular Muscle and Myoneuronal Junction

• Lee SY
• Kim SP

Abstract

After direct superior rectus muscle injection of BtA in rabbit eyes, we examined the ultrasructural changes of the muscles from 1 day to 8 weeks after injection. The most profound changes seen at electron microxcopic levels after BtA injedtion were early vacuolization of the sarcoplasmic structure, extensive damage of myofibril, degeneration of the postjunctional fold and widening of the synaptic cleft. Myofiber changes were reversible with no apparent long-term consequence. However, most of the degenerations of myoneuronal junction were still present in 8 weeks post-injedtion. Comparing myotoxic effects according to rabbit age, the botulinum toxin seems to make more severe histologic damage in the fibers of the two-month old than six-month old or older. AchE activity of injection group is mildly decrease in number of positive fibers rather than control group, which was not statistically significant in the quantitative analysis. In conclusion the early vacuolization and degeneration of the sarcoplasmic structure, and degeneration of the postjunctional folds after toxin injection in the muscles are most likely due to a direct myotoxic effect of BtA.

Keyword

Acetylcholinestrase; Botulinum toxin type A; Myoneuronal junction; Myotoxic

MeSH Terms

Botulinum Toxins*
Botulinum Toxins, Type A
Muscles
Myofibrils
Botulinum Toxins
Botulinum Toxins, Type A