Experimental design of ligand treatment using label-swap. Neuroblastoma BE(2)-M17 cells were treated with 10 μM pilocarpine for 5 min (A), with 10 ng/mL EGF for 10 min (B), or with 10 μM muscarine for 1, 5, and 20 min (C). In replicated sets, labeled conditions of treatment and control were swapped in both SILAC doublet and triplet.