Colocalization of SP-IR and CGRP-IR in axon bundles and ICGs.
A-C: Colocalization of SP-IR and CGRP-IR in an axon bundle. A large axon bundle entered the right atrium and most SP-IR (B, Red) fibers were found to have colocalization of CGRP-IR (A, Green), indicating coexpression of CGRP with SP (C,Yellow in the merged image). D-F and G-I: Two examples of colocalization of SP-IR and CGRP-IR in ICGs. Single confocal optic images show CGRP-IR terminal varicosities (D or G). Single confocal optic images show SP-IR terminal varicosites (E or H). The merged images of panel D (or G) withpanel E (or H) is shown in F (or I). PNs are in gray color. Most SP-IR varicose terminals show colocalization of CGRP-IR in their terminal varicosities. Colocalization of SP and CGRP in these terminals is signified by yellow in the composite image. Varicosities in pure green (CGRP-IR) color in panel F or I suggest that although most SP-IR fibers show colocalized CGRP expression, some fibers show exclusive CGRP immunoreactivity. Scale bars in A: 50μm for A-C, in D: 50μm for D-F, in G: 50μm for G-I.