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Age‐related remodeling of neuromuscular junctions on type‐identified diaphragm fibers
Author(s) -
Prakash Y.S.,
Sieck Gary C.
Publication year - 1998
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(199807)21:7<887::aid-mus6>3.0.co;2-2
Subject(s) - neuromuscular junction , postsynaptic potential , phrenic nerve , anatomy , diaphragm (acoustics) , fiber type , acetylcholine receptor , biology , synapse , chemistry , neuroscience , respiratory system , medicine , receptor , skeletal muscle , physics , acoustics , loudspeaker
Previous studies have reported fiber‐type differences in the morphological adaptations of neuromuscular junctions (NMJs) to aging by comparing limb muscles consisting of predominantly type I or II fibers. A confounding factor in these studies is age‐related change in activity, which may differ between muscles. In the present study, we assessed age‐related changes of the NMJ in type‐identified fibers of the rat diaphragm muscle, which maintains consistent inspiratory‐related activation throughout life. In 6‐ and 24‐month‐old rats, a fluorescent triple‐labeling technique was used to visualize phrenic axons, presynaptic nerve terminals, and postsynaptic acetylcholine receptors (end‐plates) on type‐identified fibers. The NMJs were then imaged using three‐dimensional (3D) confocal microscopy. On type IIx and IIb fibers, nerve terminal and end‐plate 2D planar and 3D surface areas expanded, and the number of nerve terminal and end‐plate branches increased, indicating fragmentation of the NMJ with aging. On the other hand, NMJs on type I and IIa fibers displayed little adaptation. These morphological adaptations may be geared toward maintaining the efficacy of inspiratory‐related activity of the diaphragm muscle, but may affect the functional reserve of the aging diaphragm. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:887–895, 1998.