SDN-1 controls AChR synaptic content. (A) Schematics of neuromuscular innervations in C. elegans. Inset: Excitatory (cholinergic) and inhibitory (GABAergic) synapses innervating a muscle cell. DNC, dorsal nerve cord; VNC, ventral nerve cord. (B) Confocal detection and quantification of cholinergic active zones using the CLA-1-BFP marker under control of the Punc-17 promoter. (C and D) Confocal detection and quantification of L-AChR (UNC-29-RFP knock-in; C) and N-AChR (ACR-16-wrmScarlet knock-in; D) fluorescence. (E and F) Representative traces of isolated L-AChR (E) or total AChR (F) synaptic currents evoked by a 10-ms optogenetic stimulation (arrowheads) of cholinergic motoneurons. Isolation of L-AChR currents was achieved by blocking N-AChR with DHβE. (G and H) Representative traces and quantification of peak currents evoked by pressure application of 0.1 mM levamisole (G) or nicotine (H) on muscle cells. Arrowheads mark the 100-ms application onsets. Individual values are shown as dots in E and F. In this figure and all other figures, confocal images are sums of Z-stacks acquired along the dorsal nerve cord by a spinning disk confocal microscope; anterior is to the left. Scale bars, 10 µm (B–D). For the quantification of fluorescence levels, data were normalized to the mean value of the control group. In this figure and all other figures, data distribution in each group is presented as violin plots showing lower and upper quartiles (dotted lines) and median value (blue line). The number of animals analyzed is indicated on the violin plot. See also Fig. S1.