Inhibition of HB-GAM bead-induced dispersal of pre-patterned AChR clusters by NSC-87877. R-BTX-labeled muscle cells were stimulated overnight with HB-GAM beads in the absence (A, B) or presence of 1 μM NSC-87877 (C, D). In control cells only bead-induced AChR clusters were present (B; asterisks) but in the NSC-treated cells both bead-induced (D; asterisks) and pre-patterned AChR clusters (arrows) were detected. The number of pre-patterned AChR clusters in bead-stimulated cells and the fraction of beads that induced new AChR clusters were quantified from multiple experiments using 0.1 or 1 μM NSC and the results were normalized relative to cells maintained in control medium (E, F). NSC-treatment inhibited the dispersal of pre-patterned AChR clusters but did not significantly affect the induction of new AChR clusters by HB-GAM beads. Control, n = 95; 0.1 μM NSC, n = 115; 1 μM NSC, n = 129; *p < 0.05, 1 μM NSC relative to control.