Figure 4. sUNC-13 Weakens Synaptic Depression and Accelerates Synaptic Recovery.

Synaptic depression and recovery were investigated by applying a train (1 Hz and 5 Hz) or a paired light stimulus onto the ventral nerve cord of UNC-13L (blue) and sUNC-13 (red) rescue worms with expression of ChIEF in their cholinergic motor neurons.

(A) Example traces of 1-Hz light train stimulus-evoked EPSCs from UNC-13L and sUNC-13 rescue animals.

(B) Quantification of synaptic depression by normalizing the EPSC amplitude (EPSC_i) to the first EPSC amplitude (EPSC₁) (n = 19 for UNC-13L rescue and n = 16 for sUNC-13 rescue).

(C) Averaged depression τ of the normalized EPSC amplitude in (B).

(D) Example traces of 5-Hz light train stimulus-evoked EPSCs from the same genotypes as in (A).

(E) Quantification of synaptic depression by normalizing the EPSC_i to EPSC₁ (n = 13 for UNC-13L rescue and n = 9 for sUNC-13 rescue).

(F) Averaged depression τ of the normalized EPSC amplitude in (E).

(G and I) Averaged cumulative EPSC amplitudes during 1-Hz (G) and 5-Hz (I) trains.

(H and J) Quantification of the replenishment rates in (G) and (I), respectively.

(K) Evoked EPSCs triggered by a paired light stimulus with various intervals ranging from 50 ms to 5 s.

(L) Averaged synaptic recovery, calculated by the ratio of EPSC₂ to EPSC₁, in UNC-13L and sUNC-13 rescue animals (UNC-13L rescue, 50 ms n = 6, 100 ms n = 6, 200 ms n = 10, 500 ms n = 7, 1 s n = 11, 5 s n = 7; sUNC-13 rescue, 50 ms n = 7, 100 ms n = 9, 200 ms n = 7, 500 ms n = 6, 1 s n = 7, 5 s n = 6).

Data in (B), (E), (G), (I), and (L) are presented as mean ± SEM, and all other data are shown as box-and-whisker plots with both median (line) and mean (cross) indicated. **p < 0.01, ***p < 0.001 compared with UNC-13L rescue; Student’s t test for data in (B), (E), and (L); Mann-Whitney test for data in (C), (H), and (J). The number of worms analyzed for each genotype is indicated under each box.