Structural alterations induced by botulinum toxin injection in juvenile versus adult rat muscle.

OBJECTIVE To investigate whether botulinum neurotoxin type A (BoNT-A) injections produce the same structural changes in juvenile and adult muscle. METHODS The present study was carried out in the Department of Anatomy, Faculty of Medicine, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia from October 2010 to May 2011. A total of 32 adult and 32 juvenile rats were used. Electron microscopy and immuno-histochemical techniques were used to conduct the morphological study. Neurofilament immunohistochemistry method was used. RESULTS The results indicate that the use of BoNT-A injections induced morphological changes in the form of muscle fiber atrophy, disorganization of the muscle fiber structure, extension of nerve terminal sprouts, and formation of new neuromuscular junctions. The same set of structural changes took place in both groups. However, the time scale of these changes occurred earlier in juvenile rats than adult muscle. CONCLUSION The injection of BoNT-A leads to morphological changes in juvenile and adult rat muscle. These changes were the same in both groups.