The ultrastructural localization and quantitation of cholinergic receptors at the mouse motor endplate

Porter, Carl W.; Barnard, Eric A.; Chiu, Tsung‐Hong

doi:10.1007/bf01868086

Cited by 36 publications

(24 citation statements)

References 29 publications

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“…The affinity of the muscle receptor for d-TC found here is an agreement with that estimated pharmacologically by a null-point method: 3.9 X 10m7 M (at 30°C) for innervated hamster diaphragm [22]. Since the denervated muscles show in situ a lower apparent affinity for d-TC [21], possibly a change in the direction of increased affinity for this antagonist occurs upon solubilization.…”

Section: Resultssupporting

confidence: 81%

“…In contrast, in the intact innervated muscle, 50% of the toxin-binding sites at the endplates are readily protected by d-TC [ 11. The d-TC-insensitive fraction is only 35% in the intact denervated mouse diaphragm muscle [21] . As 80% of the total BuTX-binding sites are solubilized by detergent [4] it is possible that the d-TC-insensitive fraction remains insoluble, or is a different compcnent that is not purified with the true ACh-binding receptor.…”

Section: Resultsmentioning

confidence: 91%

See 1 more Smart Citation

Affinity of cholinergic ligands for the partially purified acetylcholine receptor from mammalian skeletal muscle

Dolly¹,

Barnard²

1974

FEBS Letters

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 91%

Affinity of cholinergic ligands for the partially purified acetylcholine receptor from mammalian skeletal muscle

Dolly¹,

Barnard²

1974

FEBS Letters

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“…Morphometric analysis was performed on postsynaptic structures formed at the site of the original endplate in the absence of the nerve or at an ectopic position of the regenerated myofiber by interaction of the nerve and muscle . Although variation in the depth of the primary cleft occurred, there was little difference between the overall structure of regenerated postsynaptic structures and that of endplates of uninjured muscles.The density of acetylcholine receptors (AChR) at innervated motor endplates of skeletal muscle has been determined by both physiological (23, 25) and morphological (16,28,30,(33)(34)(35) means. Various studies (for review see reference 12) have shown that the number of AChR at endplates in mice (2), rats (14, 31), frogs (31), and humans (13) is quite similar.…”

mentioning

confidence: 99%

“…Various studies (for review see reference 12) have shown that the number of AChR at endplates in mice (2), rats (14, 31), frogs (31), and humans (13) is quite similar. Electron microscope autoradiographic studies have demonstrated a relatively constant density (16,28,30,(33)(34)(35) and distribution (16,(33)(34)(35) of AChR at endplates of vertebrate skeletal muscle .When skeletal muscle grafts are made, the neuromuscular junctions are disrupted by the degeneration of the myofibers and the nerves that supply them (7,10,29,37, and footnote 1).' Carlson, B. M., P. Hnik, S. Tucek, R. Vejsada, and D. Bader. …”

mentioning

confidence: 99%

Density and distribution of α-bungarotoxin-binding sites in postsynaptic structures of regenerated rat skeletal muscle

Bader¹

1981

The Journal of Cell Biology

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Acetylcholine receptors (AChR) are organized in a discrete and predictable fashion in the postsynaptic regions of vertebrate skeletal muscle . When muscle is damaged, nerves and myofibers including muscular elements of the endplate degenerate, but the connective tissue elements survive. Muscle fibers regenerate within the basal lamina of the original myofiber . Postsynaptic differentiation in regenerated mammalian skeletal muscle can occur in different ways : (a) at the site of the original endplate in the presence or absence of the nerve, or (b) at ectopic regions of the regenerated myofiber in the presence of the nerve when the original endplate is not present. The present study used '251-a-bungarotoxin (1251 -a-BuTX) and EM autoradiography to examine the density and distribution of AChR in postsynaptic structures regenerated at the site of the original endplate in the absence of the nerve and at ectopic sites of the myofiber in the presence of the nerve when the original endplate was removed . In regenerated myofibers, the density of a-BuTX-binding sites fell within the range of densities observed in uninjured muscle whether postsynaptic differentiation occurred at the site of the original endplate in the absence of the nerve or at an originally ectopic position of the regenerated myofiber . In addition, the distribution of a-BuTX-binding sites within the regenerated postsynaptic regions closely resembled the distribution of a-BuTX-binding sites in uninjured muscle . Morphometric analysis was performed on postsynaptic structures formed at the site of the original endplate in the absence of the nerve or at an ectopic position of the regenerated myofiber by interaction of the nerve and muscle . Although variation in the depth of the primary cleft occurred, there was little difference between the overall structure of regenerated postsynaptic structures and that of endplates of uninjured muscles.The density of acetylcholine receptors (AChR) at innervated motor endplates of skeletal muscle has been determined by both physiological (23, 25) and morphological (16,28,30,(33)(34)(35) means. Various studies (for review see reference 12) have shown that the number of AChR at endplates in mice (2), rats (14, 31), frogs (31), and humans (13) is quite similar. Electron microscope autoradiographic studies have demonstrated a relatively constant density (16,28,30,(33)(34)(35) and distribution (16,(33)(34)(35) of AChR at endplates of vertebrate skeletal muscle .When skeletal muscle grafts are made, the neuromuscular junctions are disrupted by the degeneration of the myofibers and the nerves that supply them (7,10,29,37, and footnote 1).' Carlson, B. M., P. Hnik, S. Tucek, R. Vejsada, and D. Bader. 338It has been established that synapses are formed in the regenerated muscle of amphibians (29, 37) and mammals (1,3,10). Marshall et al . (29) have shown that, in regenerating frog muscle, neuromuscular connections are almost always at the site of the original endplate . Burden et al . (7) have demonstrated that postsyna...

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“…At the motor endplate of vertebrate skeletal muscles acetylcholine (AcCh) is known to bind specifically to receptor molecules, which logically should be in the postsynaptic membrane (1-3). The only direct determination of receptor distribution at the endplate (4,5) and for the electroplaque (6), has been by autoradiography in the electron microscope of tissues treated with a radioactive a-neurotoxin, such as a-bungarotoxin (I3uTX), which reacts specifically and essentially irreversibly with cholinergic nicotinic receptors (7)(8)(9)(10). Thus, an average density of 8500 AcCh receptor active centers per pgm2 of postsynaptic membrane has been determined for mouse diaphragm endplates (5).…”

mentioning

confidence: 99%

The Density of Acetylcholine Receptors and Their Sensitivity in the Postsynaptic Membrane of Muscle Endplates

Albuquerque

Barnard

Porter

et al. 1974

Proc. Natl. Acad. Sci. U.S.A.

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authors have requested readers to note that a p-D-glutamyl residue rather than the p-LIglutamyl residue, implied in the text, was used for the calculations. The conclusions drawn in the paper are correct, since the D and L configurations of the p-glutamyl residue adopt almost identical conformations in thyrotropin releasing factor (TRF). It is possible to use the results in Tables 2-4 of the original paper to obtain the lowenergy conformations of TRF by simply reversing the sign of {,. The conformations thus obtained will not be the exact energy minima, but will represent all of the low-energy conformations closely. In order to illustrate this point, the calculations of Table 2 in the original text (for "p-D-glutamyl" TRF) were repeated using a p-L-glutamyl residue, and the minimum-energy results are given below ( Table 1). The dihedral angles for all conformations are essentially the same except that the sign of {l is reversed. It should be noted that the N8 conformer of structure D is now only 0.1 kcal/mol higher in energy than conformer NE of structure A. The similarity of the "p-D-glutamyl" and "p-L-glutamyl" TRF conformations suggests that the former should be active as a thyrotropin releasing factor.

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The ultrastructural localization and quantitation of cholinergic receptors at the mouse motor endplate

Cited by 36 publications

References 29 publications

Affinity of cholinergic ligands for the partially purified acetylcholine receptor from mammalian skeletal muscle

Affinity of cholinergic ligands for the partially purified acetylcholine receptor from mammalian skeletal muscle

Density and distribution of α-bungarotoxin-binding sites in postsynaptic structures of regenerated rat skeletal muscle

The Density of Acetylcholine Receptors and Their Sensitivity in the Postsynaptic Membrane of Muscle Endplates

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