Neuronal organization and cell interactions of the cat stellate ganglion

The functional structure of the cat stellate ganglion (SG) and, in particular, its extra- and intraganglionic connections and neuronal organization, were investigated using histochemical, immunohistochemical, morphological and histological methods. Retrograde axonal transport of horseradish peroxidase was used to determine most of the extraganglionic interactions. Of the targets tested, the most extensive efferent connections of the SG were with the sternocleidomastoid muscle, trachea, esophagus and heart. Neurons of the SG also send a small number of postganglionic efferents to the thyroid and stomach. Furthermore, ganglion cells send axons to the spinal ganglia. Several afferent connections of the SG were determined. Sympathetic preganglionic neurons of segments C8–T10 of the spinal cord, sensory neurons of C8–T9 spinal ganglia, intramural ganglia of the thoracic viscera and the reticular formation of the medulla oblongata send their axons to the SG. Intraganglionic interactions of interneurons with principal ganglionic cells were assumed to occur, based on the presence of interneurons immunoreactive to GABA and substance P. GABA- and substance P-immunoreactive fibers located around a small number of postganglionic neurons were also identified. Morphological study revealed asymmetry between the left and right ganglia: the right ganglion is larger than the left and contains more cells. This asymmetry was also reflected in basic structural parameters of neurons, such as average neuronal area and average diameter of cell somata. The present data has been used to develop a scheme for the basic inter- and intraneuronal connections of the cat SG. This ganglion is a true nervous center, with postganglionic neurons, some of which might be performing sensory functions, and interneurons. The ganglion is connected not only with the spinal cord and spinal ganglia, but also with neurons of the intramural ganglia and, by direct links, with efferent neurons of the medulla oblongata. Thus, the SG may play an essential role in viscera-visceral reflexes.