title: Quantitation of junctional and extrajunctional acetylcholine receptors by electron microscope autoradiography after 125I-alpha-bungarotoxin binding at mouse neuromuscular junctions.
abstract: The distribution and quantitation of 125I-alpha-bungarotoxin (alpha-BTX) binding sites and thus acetylcholine receptor (AChR) were determined in mouse sternomastoid muscle by electron microscope autoradiography. We found that a valid criterion for receptor saturation at the neuromuscular junction was the complete elimination of neurally evoked tetanic muscle contractions, since, when such a criterion was used for the endpoint of toxin incubation, alpha-BTX was bound to approximately 90% of total available endplate sites. When, without implying localization, the presynaptic axonal membrane was used as a convenient reference structure, the concentration of alpha-BTX relative to this membrane was determined to be 46,000 +/- 27% sites/mum2.
mesh_terms: D000109:Acetylcholine; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D008566:Membranes / Q000648:ultrastructure; D051379:Mice; D008954:Models, Biological; D009132:Muscles / Q000294:innervation / Q000648:ultrastructure; D009469:Neuromuscular Junction / Q000378:metabolism / Q000648:ultrastructure*; D011955:Receptors, Drug; D013570:Synaptic Membranes / Q000648:ultrastructure
chemical_list: D011955:Receptors, Drug; D000109:Acetylcholine