Presence and Colocalization of Type-1 Cannabinoid Receptors with Acetylcholine Receptors in the Motor End-Plate of Twitch Skeletal Muscle Fibers in the Frog

Na current density and membrane capacitance were studied with the loose patch voltage clamp technique on rat fast- and slow-twitch skeletal muscle fibers at three different regions on the fibers: 1) the end plate border, 2) greater than 200 microns from the end plate (extrajunctional), and 3) on the end plate postsynaptic membrane. Fibers were treated with collagenase to improve visualization of the end plate and to enzymatically remove the nerve terminal. The capacitance of membrane patches was similar on fast- and slow-twitch fibers and patches of membrane on the end plate had twice the capacitance of patches elsewhere. For fast- and slow-twitch fibers, the sizes of the Na current normalized to the area of the patch were as follows: end plate greater than end plate border greater than extrajunctional. For both types of fibers, the amplitudes of the Na current normalized to the capacitance of the membrane patch were as follows: end plate approximately end plate border greater than extrajunctional. At each of the three regions, the Na current densities were larger on fast-twitch fibers and fast-twitch fibers had a larger increase in Na current density at the end plate border compared with extrajunctional membrane.

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Defective Acetylcholine Receptor Subunit Switch Precedes Atrophy of Slow-Twitch Skeletal Muscle Fibers Lacking ERK1/2 Kinases in Soleus Muscle

Scientific Reports ◽

10.1038/srep38745 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 5

Author(s):

Shuo Wang ◽

Bonnie Seaberg ◽

Ximena Paez-Colasante ◽

Mendell Rimer

Keyword(s):

Skeletal Muscle ◽

Acetylcholine Receptor ◽

Soleus Muscle ◽

Muscle Fibers ◽

Neuromuscular Synapse ◽

Fiber Morphology ◽

Skeletal Muscle Fibers ◽

Slow Twitch

Abstract To test the role of extracellular-signal regulated kinases 1 and 2 (ERK1/2) in slow-twitch, type 1 skeletal muscle fibers, we studied the soleus muscle in mice genetically deficient for myofiber ERK1/2. Young adult mutant soleus was drastically wasted, with highly atrophied type 1 fibers, denervation at most synaptic sites, induction of “fetal” acetylcholine receptor gamma subunit (AChRγ), reduction of “adult” AChRε, and impaired mitochondrial biogenesis and function. In weanlings, fiber morphology and mitochondrial markers were mostly normal, yet AChRγ upregulation and AChRε downregulation were observed. Synaptic sites with fetal AChRs in weanling muscle were ~3% in control and ~40% in mutants, with most of the latter on type 1 fibers. These results suggest that: (1) ERK1/2 are critical for slow-twitch fiber growth; (2) a defective γ/ε-AChR subunit switch, preferentially at synapses on slow fibers, precedes wasting of mutant soleus; (3) denervation is likely to drive this wasting, and (4) the neuromuscular synapse is a primary subcellular target for muscle ERK1/2 function in vivo.

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Arpp, a New Homolog of Carp, Is Preferentially Expressed in Type 1 Skeletal Muscle Fibers and Is Markedly Induced by Denervation

Laboratory Investigation ◽

10.1038/labinvest.3780459 ◽

2002 ◽

Vol 82 (5) ◽

pp. 645-655 ◽

Cited By ~ 62

Author(s):

Yoshiyuki Tsukamoto ◽

Takao Senda ◽

Toshiya Nakano ◽

Chisato Nakada ◽

Takehiko Hida ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Fibers ◽

Skeletal Muscle Fibers

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The ultrastructure of peripheral nerve, motor end-plate and skeletal muscle in patients suffering from spinal muscular atrophy with respiratory distress type 1 (SMARD1)

Acta Neuropathologica ◽

10.1007/s00401-005-1056-y ◽

2005 ◽

Vol 110 (3) ◽

pp. 289-297 ◽

Cited By ~ 24

Author(s):

Alexander Diers ◽

Marcel Kaczinski ◽

Katja Grohmann ◽

Christoph Hübner ◽

Gisela Stoltenburg-Didinger

Keyword(s):

Skeletal Muscle ◽

Peripheral Nerve ◽

Respiratory Distress ◽

Spinal Muscular Atrophy ◽

Muscular Atrophy ◽

End Plate ◽

Motor End Plate

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Heterogeneity of type 1 skeletal muscle fibers revealed by monoclonal antibody to slow myosin

Muscle & Nerve ◽

10.1002/mus.880070507 ◽

1984 ◽

Vol 7 (5) ◽

pp. 380-387 ◽

Cited By ~ 61

Author(s):

Saiyid A. Shafiq ◽

Teruo Shimizu ◽

Donald A. Fischman

Keyword(s):

Skeletal Muscle ◽

Monoclonal Antibody ◽

Muscle Fibers ◽

Slow Myosin ◽

Skeletal Muscle Fibers

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Effect of agrin on the distribution of acetylcholine receptors and sodium channels on adult skeletal muscle fibers in culture.

The Journal of Cell Biology ◽

10.1083/jcb.115.3.765 ◽

1991 ◽

Vol 115 (3) ◽

pp. 765-778 ◽

Cited By ~ 14

Author(s):

M T Lupa ◽

J H Caldwell

Keyword(s):

Skeletal Muscle ◽

Acetylcholine Receptors ◽

Muscle Fibers ◽

Postsynaptic Membrane ◽

Na Channel ◽

High Concentration ◽

Achr Cluster ◽

Adult Skeletal Muscle ◽

Skeletal Muscle Fibers ◽

Alpha Bungarotoxin

We used the loose patch voltage clamp technique and rhodamine-conjugated alpha-bungarotoxin to study the regulation of Na channel (NaCh) and acetylcholine receptor (AChR) distribution on dissociated adult skeletal muscle fibers in culture. The aggregate of AChRs and NaChs normally found in the postsynaptic membrane of these cells gradually fragmented and dispersed from the synaptic region after several days in culture. This dispersal was the result of the collagenase treatment used to dissociate the cells, suggesting that a factor associated with the extracellular matrix was responsible for maintaining the high concentration of AchRs and NaChs at the neuromuscular junction. We tested whether the basal lamina protein agrin, which has been shown to induce the aggregation of AChRs on embryonic myotubes, could similarly influence the distribution of NaChs. By following identified fibers, we found that agrin accelerated both the fragmentation of the endplate AChR cluster into smaller patches as well as the appearance of new AChR clusters away from the endplate. AChR patches which were fragments of the original endplate retained a high density of NaChs, but no new NaCh hotspots were found elsewhere on the fiber, including sites of newly formed AChR clusters. The results are consistent with the hypothesis that extracellular signals regulate the distribution of AChRs and NaChs on skeletal muscle fibers. While agrin probably serves this function for the AChR, it does not appear to play a role in the regulation of the NaCh distribution.

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