Figure 7

Anterogradely labeled single spinal afferent axons with several branches in the circular muscle of the (a) fundus and (b) corpus. (a, b) Contour of a representative fundus and corpus and the location of the single axon within the corresponding tissue. (a’, b’) Neurolucida tracing of these axons. (a’1, a’2, b’1-b’3) Partial projection photomicrographs of red boxes in (a’, b’) showed the axon frequently bifurcating into varicose branches at different points of its trajectory (a’1, a’2), making a “U” turn before termination (b’1), and forming a fork-like terminal ending (b’3). (a’2’) A higher-magnification photomicrograph of the black box in (a’2) depicted the close association of varicose branches with smooth muscles (unstained, imaged with DIC). Additionally, free terminals were observed (arrows). PA = parent axon. Scale bar in (a, b) = 3 mm, in (a’) = 250 μm, in (b’) = 500 μm, in (a’2’) = 20 μm, in (b’3) = 50 μm (also applies to a’1, a’2, b’1, b’2).