[Study on the distribution of muscle spindles in the rat extensor digitorum longus muscle]

The distribution of muscle spindles (MS) in the extensor digitorum longus (EDL) muscle of the rat hind limb was morphologically studied on a series of longitudinal cryostat sections. The intrafusal muscle fibers were brownishly stained with the acetylcholinesterase reaction, and the mucopolysaccharide contained in the equatorial periaxial space was stained with alcian blue. This double-staining method made it easy for us to find the MS and to decide the equatorial portion and the whole extension of MS. From a series of camera lucida drawings the distribution of all MS was reconstructed on a sheet of paper and three-dimensionally imaged on a personal computer using image reconstructing software. The MS were distributed mainly in the superficial and lateral part of EDL muscle. Additionally, an ATPase reaction was employed to detect the red muscle fibers, and it was confirmed that their distribution of them is similar to that of MS.