Distribution of intramuscular nerves, motor endplates and muscle spindles of extensor digitorum longus in rabbits

Objective: To investigate the distribution of intramuscular nerves,motor endplates and muscle spindles of extensor digi-torum longus in rabbits. Methods: Modified Sihler's staining, acetylcholinesterase staining and hematoxylin and eosin staining were used. Results: The muscle fibers inserted into the second phalange occupied the proximal 1/3 of the belly; the rest fibers occupied the distal 2/3 of the belly. The nerve innervating extensor digitorum longus came from fibular nerve. Two extramuscular nerve trunk were seen; the upper one mainly innervated muscle fibers inserted into the second toe; the other trunk mainly distributed in the muscle fibers of rest toes. Motor endplate of all sections of extensor digitorum longus was a continuous band except coronary plane on which black staining particles diffused widely. Muscle spindle density of every part of extensor digitorum longus was as follows: the origin was 33. 95/g; the middle was 44. 76/g; and the insert was zero. Conclusion: Dense regions of intramuscular nerve branches has a large motor endplate and muscle spindle population. The extensor digitorum longus can be divided into compartments. Distributions of muscle spindle are asymmetric in extensor digitorum longus.