Figure 2.

Macrophotographs of the rabbit heart base to illustrate the location and the structure of the nerve plexus of heart hilum (NPHH) in the rabbit heart stained histochemically for acetylcholinesterase. The boxed area in (a) outlines the area on the rabbit heart that is enlarged in (b). The boxed area in (b) outlines the area on the rabbit right neuronal cluster that is enlarged as the inset (c). Black arrows point the access of extrinsic cardiac nerves into the heart through the venous part of the heart hilum. White arrowheads indicate some ganglia within the neuronal clusters. Black arrowheads point to some subplexal nerves extending to the innervation regions, while the white solid arrows in the inset (c) point to some intrinsic cardiac neurons within the right neuronal cluster (RNC). Asterisks indicate some commissural nerves that connect the neuronal clusters within the venous part of the heart hilum. Dashed line demarcates the heart hilum. DRA, dorsal right atrial subplexus; FP, fat pad under interatrial septum; FP at BPT, fat pad at bifurcation of pulmonary trunk; LNC, left neuronal cluster; RCV, root of caudal vein (inferior caval vein); RLPV, root of left pulmonary vein; RMPV, root of middle pulmonary vein; RNC, right neuronal cluster; RRCV, root of right cranial vein (superior caval vein); RRPV, root of right pulmonary vein; TS, terminal groove; VRA, ventral right atrial subplexus.