European Journal of Anatomy

Official Journal of The Spanish Society of Anatomy
Cover Volume 16 - Number 1
Eur J Anat, 16 (1): 33-42 (2012)

Site-dependent difference in the density of sympathetic nerve fibers in muscle-innervating nerves: a histologic study using human cadavers

Tadashi Nakao1, Kwang Ho Cho2, Masahito Yamamoto1, Shigeki Yamane1, Gen Murakami3, Yoshinobu Ide1, Shin-ichi Abe1,4

1Department of Anatomy, Tokyo Dental College, Chiba City, Japan 2Department of Neurology, Wonkwang University School of Medicine, Jeonbuk Regional Cardiocerebrovascular Disease Center, Institute of Wonkwang Medical Science, Iksan, Korea 3Division of Internal Medicine, Iwamizawa Kojin-kai Hospital, Iwamizawa, Japan 4Oral Health Science Center hrc-8, Tokyo Dental College, Chiba City, Japan

ABSTRACT The autonomic nerve supply of skeletal muscle has become a focus of interest because it is closely related to the adaptation of energy metabolism with aging. However, there is no comprehensive information concerning the sympathetic nerves present in muscle-innervating nerves (muscle-nerve). At the point of entry of muscle-nerves into 8 striated muscles (the soleus, extensor carpi radialis, infraspinatus, genioglossus, extra- ocular medial rectus, temporalis, lateral pterygoid, and digastricus anterior belly) in 15 cadavers of elderly people, we counted both tyrosine hydroxylasepositive nerve fibers (TH- fibers) and motor nerve fibers to estimate the ratio of THfiber/ motor fibers. The 3 limb muscles were found to have a high ratio (soleus, 58%; infraspinatus; 45%; extensor, 36%), whereas the 4 head muscles (digastricus, 23%; genioglossus, 15%; temporalis, 10%; lateral pterygoid, 6%; medial rectus, 1%) had relatively low ratios. The site- dependent characteristics of the THfibers seemed to reflect their commitment to muscle activity. However, some discrepant characteristics were noted: 1) In spite of the tonic and continuous activity required for both the genioglossus and infraspinatus, the proportions of TH-fibers were quite different between the tongue and the shoulder muscles; 2) Likewise, the soleus and extra-ocular rectus showed a considerable difference, even though rapid and phasic contraction is essential for both muscles. Rather than reflecting the influence of postnatal functional demand, these site- dependent characteristics might develop as a result of differences in sympathetic innervation of the striated muscles during fetal development, i.e., a short course along the arteries feeding the head muscles, or a long course along the muscle-nerves to the limb muscles.

Keywords: Tyrosine hydroxylase-positive nerve fibers, Sympathetic innervation, Striated muscles, Feeding artery, Muscle hilus

European Journal of anatomy
ISSN 2340-311X (Online)