Synaptic depression and recovery were investigated by applying a train (1 Hz or 5 Hz) or a paired light stimulus onto the ventral nerve cord of the adult worms with expression of ChIEF in cholinergic motor neurons. (A, C) Example traces of 1 Hz and 5 Hz light train stimulus-evoked EPSCs (black, wild-type; red, unc-10(K77/79E) mutants). (B, D) Quantification of synaptic depression by normalizing the EPSC amplitude (EPSCi) to the first EPSC amplitude (EPSC1). (E) Evoked EPSCs triggered by a paired light stimulus with various intervals ranging from 0.05 s to 5 s. (D) Synaptic recovery calculated by the ratio of EPSC2 to EPSC1 (wild-type, 50 ms = 7, 100 ms = 8, 200 ms = 11, 500 ms n = 7, 1 s n = 18, 5 s n = 8; unc-10(nu487 K77/79E) mutant, 50 ms = 5, 100 ms = 7, 200 ms = 11, 500 ms n = 10, 1 s n = 14, 5 s n = 7). Data are mean ± SEM (n.s., non-significant when compared to wild-type; student’s t-test).