Figure 7.

Soleus muscle preparations from WT and Egr-1−/− mice were subjected to electrophysiological recordings. Twenty-one NMJs were recorded from five different WT mice, and 26 NMJs were recorded from five different Egr-1−/− mice. (A) Representation of spontaneous miniature endplate potential (MEPP) recordings from WT and Egr−/− mouse soleus NMJS. There was no significant difference in the mEPP frequency, (B) or amplitude, (C) in WT vs. Egr-1−/− mouse soleus NMJs. (D) Representation of Endplate potentials (EPPs) evoked by paired-pulse stimulation of the motor nerve (15 ms interval) from WT and Egr-1−/− mouse soleus NMJs. The EPP amplitude was similar in Egr-1−/− and WT mice, (E) but Egr-1−/− mice displayed an increase in quantal content (F,G). There was no significant difference in the paired-pulse facilitation (PPF) between genotypes. To analyze the electrophysiology results according to fiber type, each NMJ recording was sorted according to fiber type and analyzed. There were no significant differences in the mEPP frequency, (H) or amplitude, (I) between genotypes in type I or type IIa fibers. There was no significance difference in EPP amplitude in either fiber type (J–L), although the quantal content was increased in type IIa fibers (L,M). There was no significant difference in PPF between genotypes when sorted by fiber type. p-values were obtained using Student’s t-tests or 2-way ANOVA, respectively. *(p ≤ 0.05); **(p ≤ 0.01); ***(p ≤ 0.001); ****(p ≤ 0.0001).