Fig. 5: 3D analysis of the intramuscular innervation pattern during postnatal development.

a–c The spatial conformation of intramuscular motor nerves in a P0 cleidomastoid (a), P6 biceps brachii (b), and P3 gastrocnemius (c). d–f The segmentation of the nerve branches in a–c by 3D tracing using the Imaris software. The primary branches were noted as originating from the nerve branches entering the muscles and extending from proximal to distal, and they were numbered and marked with different colors. g–i The distribution of secondary branches in the 2^# primary branch of the cleidomastoid (g), 1^# primary branch of the biceps brachii (h), and 2^# primary branch of the gastrocnemius (i). j–l The quantification of the primary and secondary branches in the cleidomastoid (j), biceps brachii (k), and gastrocnemius (l) during postnatal development and adulthood (n = 3 independent animals for each muscle at each time point). Scale bar: 100 μm. All values are presented as the means ± SEM; statistical significance in j–l (n.s. represents not significant) was assessed using one-way ANOVA.