Sigmastat v4

APs were recorded extracellularly using a low-noise AC differential amplifier (DAM 80, World Precision Instruments, Sarasota, FL). The activity was monitored on-line, filtered (0.3 to 10 kHz), amplified (x10,000), digitized at 20 kHz using a 1401 interface (CED, Cambridge, UK), and stored on a PC. APs were discriminated off-line using Spike 2 software (CED). The root-mean-square (RMS) value of pre-stimulus noise was calculated and 5 times that value was set as the detection threshold for AP spikes. The time at which the stimulus first exceeded the threshold was deemed as the onset of the AP. To avoid erroneous discrimination, we only studied single-unit APs temporarily separated from other neural activities by at least 3 msec in any record. CDs were measured as the time between the onset of stimulus artifact and the onset of recorded APs. CV was computed from the CD and the distance between stimulating and recording electrodes. Axial stretch was quantified by stretch ratio λ (i.e., the deformed nerve length divided by the in vitro nerve length at the zero-stretch state). The zero-stretch nerve length was measured as the distance between the proximal and distal ligatures (Fig. 7A). Data were presented as means ± standard error (SE). Statistical analysis was performed using SigmaStat v4.0 (Systat Software, San Jose, CA). Differences were considered significant when p < 0.05.

All the data are presented as mean value ± standard error of the means (SEM) unless otherwise noted. Following a test for normality, either Student’s unpaired t test (for two groups) or one/two-way ANOVA (for more than two groups) was used for normally distributed data (Figs 2, 3 and 7). Data with a non-normal distribution was analysed with a Kruskal-Wallis one-way ANOVA within each genotype (Ca²⁺ spark full width, half-maximum (FWHM), full duration, half maximum (FDHM) and amplitude, Fig. 4) or with Friedman’s repeated measures ANOVA across all groups (Ca²⁺ spark frequency, Figs 4 and 6) with a corrected Bonferonni post hoc test for multiple comparisons (SigmaStat v 4.1 (Systat Software, Inc., San Jose, CA, USA) and SPSS Statistics v 26 (IBM Corp., Armonk, NY, USA)).