Localization of sympathetic, parasympathetic and sensory neurons innervating the heart of the Beijing duck by means of the retrograde transport of horseradish peroxidase

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 locate d 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 ventri cle were more abundantly innervated by sympathetic neurons than the atrium. The left side of the heart was preferentially innervated by sympathetic po stganglionic neurons in the left side of paravertebral ganglia but the righ t side of the heart were equally supplied from the right and left ganglia. Within the medulla oblongata, the number of labeled vagal preganglionic neu rons 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 f ound in many ducks injected into the coronary sulcus. Cardiac sensory neuro ns were observed in the dorsal root ganglia C15 to T2 (highest in the gangl ion Tr) and in the nodose and jugular ganglia of the vagus nerve. These lab eled neurons probably form the afferent and efferent limbs of cardiac refle xes and control circulation in the Beijing duck.