Effect of streptozotocin-induced diabetes on motoneurons and muscle spindles in rats.
This study examined the alterations in the number and size of motoneurons innervating the medial gastrocnemius (MG) and biceps femoris (BF) motor nuclei in diabetic rats (12 or 22 weeks after injection of streptozotocin) and age-matched controls using retrograde labeling technique. Additionally, morphological alterations of muscle spindles in BF and MG muscles were tested. Significantly fewer labeled MG motoneurons were found in 12- and 22-week diabetic rats as compared with age-matched control animals. In contrast, the number of BF motoneurons was preserved in each group. Compared to control animals, the ratio of larger motoneurons of MG and BF muscle were decreased at 12 weeks, and smaller MG motoneurons were drastically decreased at 22 weeks. Moreover, MG muscle spindle showed reduction of its number and increase of intrafusal muscle fibers; however, BF muscle spindles showed little or no difference from control animals. We conclude that there is an early loss of alpha motoneurons for both MG and BF muscles followed by a later loss of gamma motoneurons in MG muscle in diabetic animals. Moreover, loss of gamma motoneuron might induce atrophy of MG muscle spindles.
Department of Physical Therapy, Health Science University, Yamanashi, Japan. Electronic address: k.muramatsu@kenkoudai.ac.jp.
Ken
K
Muramatsu
Department of Occupational Therapy, Kyorin University, Tokyo, Japan.
Masatoshi
M
Niwa
Department of Physical Therapy, Health Science University, Yamanashi, Japan.
Toru
T
Tamaki
Department of Physical Therapy, Health Science University, Yamanashi, Japan.
Masako
M
Ikutomo
Department of Physical Therapy, Health Science University, Yamanashi, Japan.
Yujiro
Y
Masu
Division of Human Environmental Science, Mount Fuji Research Institute, Yamanashi, Japan.
Tatsuya
T
Hasegawa
Department of Occupational Therapy, Health Science University, Yamanashi, Japan.
Satoshi
S
Shimo
Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, Ibaraki, Japan.
Sei-Ichi
SI
Sasaki
D000818:Animals; D048429:Cell Size; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000473:pathology*; D003922:Diabetes Mellitus, Type 1 / Q000139:chemically induced / Q000473:pathology*; D008297:Male; D009046:Motor Neurons / Q000473:pathology*; D009470:Muscle Spindles / Q000473:pathology*; D017208:Rats, Wistar; D013311:Streptozocin
D013311:Streptozocin
Alpha motoneuron; Denervation; Diabetes; Diabetic neuropathy; Gamma motoneuron; Muscle spindle