ABSTRACT. Distributions of the cardiac plexuses and cardiac ganglia were gross-anatomically and histologically studied in eight Beijing ducks. The cardiac plexuses consisted of two components, the cardiac nerve arising from the sympathetic trunk and the cranial and caudal cardiac nerves arising from the vagus. Branches of these nerves made the cardiac plexuses on the epicardium. The cardiac plexuses could be divided into the six plexuses, that is, the right and left coronary plexuses, pericardiac transverse sinus plexus, caudal cardiac plexus, and right and left superior cardiac plexuses. There were small ganglia in the caudal cardiac plexus and the right and left coronary plexuses. These ganglia containing multipolar neurons were found like a linking chain in a single nerve. -KEY WORDS: Beijing duck, cardiac ganglion, cardiac plexus.J. Vet. Med. Sci. 59(5): 409-411, 1997 anastomosing with each other. The trunk of the left sympathetic cardiac nerve (Fig. 1a, b-1') ran caudomedially to the surface of the left cranial vena cava (Fig. 1a, b-F'), and ramified into two or three branches. These branches anastomosed with the left caudal cardiac nerves of the vagus (Fig. 1a, b-4'). The right sympathetic cardiac nerve ( Fig. 1c-1) gave off two branches after arrival at the base of the heart. One branch ran along the dorsolateral surface of the right cranial vena cava (Fig. 1c-F). The trunk of the right sympathetic cardiac nerve ran obliquely and caudally along the caudal vena cava (Fig. 1c-G), and anastomosed with the right caudal cardiac nerves of the vagus (Fig. 1c-4). On the other hand, each vagus nerve trunk gave off the left or right cranial cardiac nerve near the nodose ganglion. The left vagal cranial cardiac nerve ( Fig. 1d-3') received branches from the left sympathetic cardiac nerve, and reached the right coronary sulcus through the arterial cone. The right vagal cranial cardiac nerve ( Fig. 1d-3) descended along the dorsal surface of the right pulmonary artery (Fig. 1d-C). Further descending, the continuation of the vagus nerve trunk (Fig. 1a, b-2', 1c-2) formed a ring of the nerve near the pulmonary vein (Fig. 1a, b-E', 1c-E) through the base of the heart. The caudal cardiac nerves (Fig. 1a, arose from the ventral branch of the ring of the vagus nerve or from the vagus nerve trunk more caudally. They anastomosed with the sympathetic cardiac nerve of each side (Fig. 1a, b-1', 1c-1).The caudal cardiac plexus (Fig. 1a, b, c-5) was formed by the sympathetic cardiac nerves (Fig. 1a, b-1', 1c-1) and vagal caudal cardiac nerves (Fig. 1a, b-4, 4', 1c-4) of both sides on the dorsal surface of the atrium. It lay on the right and left atriums and basal parts of the right and left ventricles. The left superior cardiac plexus (Fig. 1b-6') was formed by the left sympathetic cardiac nerve (Fig. 1b-1') and left caudal cardiac nerves (Fig. 1b-4') of the vagus. It was distributed on the dorsal surface of the left atrium. The right superior cardiac plexus (Fig. 1b, c, d-6) was formed by three branches: one branch from the...

ABSTRACT. Sympathetic, parasympathetic and sensory neurons were labeled by injections of horseradish peroxidase into various regions of the heart in 33 Beijing ducks. Sympathetic postganglionic neurons innervating the heart were located in the paravertebral ganglia C15 (C16 is the last cervical segment in the duck) to T3, especially in the ganglion T1. The coronary sulcus and ventricle were more abundantly innervated by sympathetic neurons than the atrium. The left side of the heart was preferentially innervated by sympathetic postganglionic neurons in the left side of paravertebral ganglia but the right side of the heart were equally supplied from the right and left ganglia. Within the medulla oblongata, the number of labeled vagal preganglionic neurons in the nucleus ambiguus was much greater than that in the dorsal motor nucleus of the vagus nerve. Labeled neurons of the nucleus ambiguus were found in many ducks injected into the coronary sulcus. Cardiac sensory neurons were observed in the dorsal root ganglia C15 to T2 (highest in the ganglion T1) and in the nodose and jugular ganglia of the vagus nerve. These labeled neurons probably form the afferent and efferent limbs of cardiac reflexes and control circulation in the Beijing duck.-KEY WORDS: autonomic nervous system, Beijing duck, heart, parasympathetic neuron, sympathetic neuron. 1999 parasympathetic preganglionic neurons innervating the heart of the pigeon were located in the nucleus ambiguus [4]. Recently, distributions of the cardiac plexus and cardiac ganglia were gross-anatomically studied in the Beijing duck [5]. Six cardiac plexuses and cardiac ganglia arising from the sympathetic trunk and the vagus nerve made the particular pattern of the autonomic nerve networks on the heart of the duck. However, few transport studies have been carried out in the duck. The present study aims at elucidating the precise anatomical distribution of sympathetic postganglionic, parasympathetic preganglionic and sensory neurons innervating each cardiac region of the Beijing duck using retrograde axonal transport of HRP. MATERIALS AND METHODSThirty-three Beijing ducks (Anas platyrhynchos var. domesticus) weighing 1-2 kg (1-2 months old) were used in this study. Under anesthesia with 30% solution of urethane (0.8 g/kg, i.v.), the heart was exposed and 20% HRP (Sigma, Type VI) was injected into the subepicardium in 1 or 3 regions of the right and left atriums, right and left ventricles and right coronary sulcus (Table 1). Injections of HRP were performed at 5 points (5 µl/point) in each cardiac region for 10-25 min. After a postinjection survival time of 30-36 hr, ducks were deeply anesthetized with 30% solution of urethane (1 g/kg, i.v.) and perfused with 0.75% saline (40°C) through the left ventricle, followed by the fixative consisting of 2% paraformaldehyde and 1.25%In the heart of birds, like that of mammals, heart rate is set by the interplay of sympathetic and parasympathetic influences on the pacemaker. Stimulation of the sympathetic cardiac nerve typically i...