Localization of sensory neurons traversing the stellate ganglion of the cat.

The distribution of sensory cells whose axons traverse the stellate ganglion and project via sympathetic cardiac nerves to the heart of the cat has been examined quantitatively. Horseradish peroxidase (HRP) injected at multiple sites in the right stellate ganglion, or applied to the middle cardiac nerve, labelled small numbers of cells in the thoracic dorsal root ganglia (DRG) from T1 to T8. These cells were most numerous between T2 and T5 and were consistently small (less than 40 micrometer) relative to other cells in the DRG. When HRP was applied to middle cardiac nerves, the numbers of labelled sensory cells always exceeded the numbers of myelinated axons counted in the same nerves from other cats. It is concluded that the distribution of the cells of cardiac sensory fibers is more extensive within thoracic DRG than has been previously reported, and it is suggested that such fibres travelling in the sympathetic cardiac nerves may be either myelinated or unmyelinated.