Redistribution of acetylcholine receptors on developing rat myotubes

The mechanism of formation of acetylcholine receptor (AChR) clusters at developing mammalian endplates was investigated in vitro, using intercostal muscles from embryonic rats. The muscles were explanted in organ culture with the spinal cord attached, as described previously (Ziskind-Conhaim, L., and M. J. Dennis (1981) Dev. Biol. 85: 243-251). AChRs on the myofibers were labeled with [125I]-alpha-bungarotoxin shortly before clusters appeared and subsequently were cultured in unlabeled toxin for 1 day. Autoradiography of the cultured fibers demonstrated the presence of labeled clusters of AChRs indicating that the AChRs in the newly formed clusters arise from AChRs that had previously been uniformly distributed on the muscle surface.