RESUMEN
The central distribution of visceral primary afferent fibers from greater splanchnic nerve of the cat have been studied. Horseradish peroxidase (HRP) dissolved in distilled water was injected into the coeliac ganglion or greater splanchnic nerve unilaterally. The HRP was taken up by afferent fibers and transported across the spinal ganglia and then anterogradely as far as central terminals in the spinal cord and medulla. The HRP reaction-product within the central processes of the primary sensory neurons was detected ipsilaterally in the Lissauer's tract, dorsal funiculus and spinal gray matter. After entering the spinal cord via the spinal dorsal roots, the great majority of labeled fibers (viz. the central processes of primary sensory neurons) were found to run longitudinally within the zone of Lissauer, and only sparse fibers to ascend in the dorsal funiculus. The medial projection fibers (MPF) and lateral projection fibers (LPF) arose periodically from the labeled fiber bundle in the Lissauer's tract to form a thin shell surrounding both the medial and lateral sides of the dorsal horn. The terminal areas of the more prominent LPF were found at laminae I, V, VII and the region surrounding the central canal, whereas the MPF ended at the medial part of lamina V and lamina X. Some smaller fiber bundles from LPF were seen to enter the cell clusters of the intermediolateral nucleus, where these fibers divided rostrocaudally and ran parallel with the longitudinal dendritic branches of the intermediolateral cells. The few labeled fibers located at the dorsal funiculus were traced to the lower medulla and the distinct terminal area of them was situated in the ventrolateral part of the nucleus gracilis at the level below the obex.