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. Author manuscript; available in PMC: 2022 Jun 1.
Published in final edited form as: J Physiol. 2021 Apr 18;599(11):2953–2967. doi: 10.1113/JP281182

Figure 3. Muscle spindle afferents of VGLUT1+/− mice have lower firing frequencies during static phase of stretch.

Figure 3.

Characteristic responses of muscle spindle afferents isolated from WT mice to static stretch (A & B). Normal stretch response in firing pattern of VGLUT1+/− mice during the ramp-and-hold stretch seen in 11 of 14 afferents (C). Three out of 14 afferents of VGLUT1+/− mice failed to consistently fire throughout stretch (D; afferent VGLUT1+/−1 shown in red and VGLUT1+/−2 shown in black; E afferent VGLUT1+/−3; same afferents shown in Fig. 4B). Boxplots of firing rates of muscle spindle afferents during IST (F) and FST (G) at all 3 stretch lengths. Line represents group median and bars represent maximum and minimum group values. Differences in average firing rates between the WT (black; n = 14) and VGLUT1+/− afferents (red; n = 14) during IST and FST significantly different as determined by a two-way ANOVA (main effect of genotype, IST p = 0.011 and FST p = 0.10). (H) Difference in firing at FST at the 7.5% Lo stretch and that of the 2.5% Lo stretch were compared between genotypes. The black line represents the mean for a given group. No significant group differences observed (p = 0.194; Mann-Whitney UTest), but 4 VGLUT1+/− afferents had values of 0 or less, something never observed in WT afferents.