Figure 5.

CGRP-IR innervation of intrinsic cardiac ganglia (ICGs) in the atria of a representative mouse.

A. Schematic drawing of the left atrium with ICGs indicated by grey patches. The dotted frame encloses ICG plexuses. B. The ICGs at the left portion as enclosed in the dotted frame in panel A were shown at higher magnification. C. A confocal projection of the ganglion region indicated by the arrow above the dotted frame in panel B. CGRP-IR axons innervated ICG neurons (autofluorescence). Varicose CGRP-IR axons traveled in the connective between ICGs. Most of these varicose axons coursed through and passed by the ganglion, whereas some formed varicose terminals around cardiac ganglionic principal neurons (PNs). D. Higher magnification of the boxed area in C showing such axonal varicosities near PNs. Noticeably, none of PNs were CGRP-IR. E. All-in-focus projection image at the AV region of the right atrium. A ganglion is identified within the dotted frame. F. High magnification of the region with the dotted frame in panel E. G-H. Two different single optical sections showing that CGRP-IR axons formed varicosities around the individual PNs (arrows). Arrowheads in E, G, and H indicate CGRP-IR axons were passing by ICG PNs. Scale bars: 200 μm in panel B; 100 μm in panel C; 10 μm in panel D. 50 μm in panel E; 50μm in F for F-H.