RESUMEN
The chemical nature of spinal ganglionic neurons, the peripheral processes of which project divergently to the somatic and visceral areas, has been identified by means of tri-labeling method of combining fluorescein tracing and immunocytochemistry. Ten rats were used. First, 2?l of 2% fast blue (FB) were injected into the left coeliac ganglion. Two days later, 2% nuclear yellow (NY) was injected into left 9-11th intercostal nerves(l?l for each). On the 4th day, animal was perfused with 10% formalin in 0.1mol/L phosphate buffer.The left Th9-11 spinal ganglia were removed and cut into sections by cryostat. The sections were observed under fluorescence microscope and photographed. The results showed that there were three kinds of neurons in the spinal ganglia: (1) single FB labeled cells with blue fluorescent cytoplasm accounted for 38.8% of total labeled cells; (2) single NY labeled cells with yellow fluorescent nuclei accounted for 52,7%; (3) FB and NY double labeled cells accounted for 8.5% and mostly were small or medium in size. Then, the double labeled cells-containing sections were further processed by substance P-demonstrating PAP immunocytochemical staining. The immunostain and fluorescent photographs in the same section were compared and identified each other. We have found that the labeling ratio of SP/NY was 1.4%; SP/FB was 7% and SP/NY+FB was 28.8%. Present study has not only identified the convergence of somato-vesceral sensation in spinal ganglia but also detected the chemical nature of these neurons(substance P) for the first time. In addition, this result has provided a morphological basis for the mechanisma of referred pain and somato-visceral reflection.