Montage of all-in-focus maximum confocal projections showing distribution of CGRP-IR nerve fibers in the right and left atrium of a FVB mouse.
A. A few large CGRP-IR axon bundles (indicated by large solid arrows) entered the right atrium from SVC and LP-CV. Then, they bifurcated into small bundles (indicated by large open arrows) and single axons (indicated by small arrows). Finally, these single axons covered all regions of the atrium with terminal networks (see Figures 2 and 3 for detail), including the auricle and the entrance area of IVC, SVC and LP-CV. In addition, CGRP-IR axons innervated multiple ICGs with varicose endings around individual cardiac ganglionic principal neurons as indicated by stars (see Figures 2 and 5 for detail). Inferior vena cava: IVC; superior vena cava: SVC; left precaval vein; LP-CV.
B. A few large CGRP-IR axon bundles (indicated by large solid arrows) entered the left atrium from left and right PVs. Then, they bifurcated into small bundles (indicated by large open arrows) and single axons (indicated by small arrows). Finally, these single axons covered all regions of the atrium with terminal networks (see Figures 2 and 3 for detail), including the auricle and the entrance area of PVs (Figure 4). In addition, CGRP-IR axons innervated multiple ICGs with varicose endings around individual cardiac ganglionic principal neurons as indicated by stars (see Figures 2 and 5 for detail). Pulmonary veins: PVs. Note: Since panels A and B are confocal montages which show the overall distribution of CGRP-IR axons, the detail structures of the axons and terminals are not visible at this magnification. The square frames A, B, and C and A1, B1, and C1 are the sampling windows where the detail structure of axon terminals will be presented in Figure 3.Scale bars: 500 μm. Note: If you are viewing the electronic version, please“zoom” in on these montages and view the details of axons, terminals and ganglia.