Figure 10

Anterogradely labeled single spinal afferent axons that arborized extensively in the corpus circular muscle. (a) Contour of a representative corpus and the location of a single spinal axon within the corpus. (a’) Neurolucida tracing of this axon. (b–d) Partial projection photomicrographs of red boxes in (a’). Panels (b, c) illustrated the arborizing feature of this axon and numerous spherical puncta-like varicosities distributed along the nerve fibers. (b1–c1) Higher-magnification photomicrographs of black boxes in (b) and (c) showed the close association of varicose branches with smooth muscles (unstained, imaged with DIC). Occasionally, large (arrowhead) and small (arrow) varicosities could be identified on the branches (c1). PA = parent axon. Scale bar in (a) = 3 mm, in (a’) = 500 μm, in (d) = 50 μm (also applies to b, c), and in (c1) = 20 μm (also applies to b1–b2).