Investigation of the nerve distribution pattern of leg muscles in rat

Information about the distribution of intramuscular nerve fibres within the skeletal muscles will enhance the understanding of their morphological structure and functions. This study was designed to examine the entire intramuscular nerve distribution pattern in rat leg muscles. The tibialis cranialis, tibialis caudalis, extensor digitorum longus, flexor digitorum longus, gastrocnemius, peroneus longus and brevis muscles were dissected from origo and insertion points under a surgical microscope in seven rats. These skeletal muscles from right hindlimbs were stained with Sihler's stain. The diameter of extramuscular and major nerve branches, number of major and minor nerve branches and anastomoses were measured and photographed under a stereomicroscope. In addition, serial sections were obtained from the left hindlimb muscles with S100 immunohistochemical staining and transferred to the computer to reconstruct images. A significant difference was found between the gastrocnemius and tibialis caudalis (p < 0.001), flexor digitorum longus and tibialis caudalis (p < 0.003), and peroneus longus and tibialis caudalis (p < 0.049) with regard to the diameter of major branches. The gastrocnemius was significantly different from the flexor digitorum longus, peroneus longus, extensor digitorum longus, tibialis caudalis and tibialis cranialis with regard to the number of minor nerve branches (p < 0.001). Knowledge of the branching pattern and some key landmarks, such as the number and diameter of major and minor nerve branches and the number of anastomoses between the nerve branches of skeletal muscles, is helpful in surgical or therapeutic interventions and botulinum toxin injections in areas of high extramuscular and intramuscular nerve density.