Experiments were performed to determine the specificity of Il25I]a-bungarotoxin binding to skeletal muscle. In adult rat diaphragm, [1251]a-bungarotoxin was found to bind almost exclusively to those regions of the muscle that contain endplates and are known to be sensitive to acetylcholine. In contrast, chronically denervated adult muscle and muscle from neonatal rats, both of which are sensiti...