Nerve terminal contributes to acetylcholine receptor organization at the dystrophic neuromuscular junction of mdx mice.
Changes in the distribution of acetylcholine receptors have been reported to occur at the neuromuscular junction of mdx mice and may be a consequence of muscle fiber regeneration rather than the absence of dystrophin. In the present study, we examined whether the nerve terminal determines the fate of acetylcholine receptor distribution in the dystrophic muscle fibers of mdx mice. The left sternomastoid muscle of young (1-month-old) and adult (6-month-old) mdx mice was injected with 60 microl lidocaine hydrochloride to induce muscle degeneration-regeneration. Some mice had their sternomastoid muscle denervated at the time of lidocaine injection. After 10 days of muscle denervation, nerve terminals and acetylcholine receptors were labeled with 4-Di-2-ASP and rhodamine-alpha-bungarotoxin, respectively, for confocal microscopy. In young mdx mice, 75% (n = 137 endplates) of the receptors were distributed in islands. The same was observed in 100% (n = 114 endplates) of the adult junctions. In denervated-regenerated fibers of young mice, the receptors were distributed as branches in 89% of the endplates (n = 90). In denervated-regenerated fibers of adult mice, the receptors were distributed in islands in 100% of the endplates (n = 100). These findings show that nerve-dependent mechanisms are also involved in the changes in receptor distribution in young dystrophic muscles. In older dystrophic muscles, other factors may play a role in receptor distribution.
Marques
Maria Julia
MJ
Department of Anatomy, Institute of Biology, State University of Campinas, São Paulo, Brazil. marques@unicamp.br
Taniguti
Ana Paula Tiemi
AP
Minatel
Elaine
E
Neto
Humberto Santo
HS
D000367:Age Factors; D000818:Animals; D004195:Disease Models, Animal; D008012:Lidocaine / Q000494:pharmacology; D051379:Mice; D018101:Mice, Inbred mdx; D018613:Microscopy, Confocal; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation / Q000378:metabolism* / Q000503:physiopathology; D009137:Muscular Dystrophy, Animal / Q000378:metabolism* / Q000503:physiopathology; D020388:Muscular Dystrophy, Duchenne / Q000378:metabolism* / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D011940:Receptor Aggregation; D011950:Receptors, Cholinergic / Q000378:metabolism*; D012038:Regeneration / Q000187:drug effects
D011950:Receptors, Cholinergic; D008012:Lidocaine