(A,B) 20 Hz stimulation (arrow) of the phrenic nerve from SOD1-G93A mice injected with the control antibody to GP120 led to a rapid and severe decline in the CMAP amplitude. In contrast, the CMAP amplitude decreased gradually and modestly in SOD1-G93A mice injected with the MuSK agonist antibody. After 5 s, the MuSK agonist improved CMAP amplitude by 13.6% in females and by 31.7% in males (n = 6–7; p<0.0001). The faint grey and blue lines indicate the SEMs. (C,D) 50 Hz stimulation (S, arrow) of the phrenic nerve in SOD1-G93A mice injected with the control antibody to GP120 led to frequent failures (F, arrow) to elicit a CMAP, whereas CMAPs were reliably elicited in SOD1-G93A mice injected with the MuSK agonist antibody, similar to the number of failures seen in wild type mice. The MuSK agonist antibody reduced the number of failures by 88% in females and 70% in males during 1 min of stimulation. The scatter plot shows the values for individual mice, as well as the mean values and SEM; *p<0.05, **p<0.01, ***p<0.001. The baseline CMAP amplitude data are as follows: anti-GP120-treated males, 5.95 ± 1.14 mV; MuSK agonist antibody-treated males, 5.93 ± 0.52 mV; anti-GP120-treated females, 4.95 ± 0.54 mV; MuSK agonist antibody-treated females, 5.81 ± 0.63 mV.