SPONTANEOUS OPENING OF THE ACETYLCHOLINE-RECEPTOR CHANNEL IN DEVELOPING MUSCLE-CELLS FROM NORMAL AND DYSTROPHIC MICE

Single-channel activity was recorded from cell-attached patches on ske letal muscle cells isolated from wild-type mice and from mice carrying the dy or mdx mutations. Spontaneous openings of the nicotinic acetyl choline receptor channel (nAChR) were detected in virtually all record ings from either dy/dy or dy/+ myotubes, but only infrequently from wi ld-type or mdx myotubes. Spontaneous openings were also present in mos t recordings from undifferentiated myoblasts from all of the mouse str ains studied. The biophysical properties of the spontaneous activity w ere similar to those of the embryonic form of the nAChR in the presenc e of acetylcholine (ACh). Examination of the single-channel currents e voked by low concentrations of ACh showed a reduced sensitivity to the agonist in the dystrophic dy and mdx myotubes, but not in wildtype my otubes. The results suggest that alterations in nAChR function are ass ociated with the pathogenesis of muscular dystrophy in the dy mouse. ( C) 1995 Wiley-Liss, Inc.