The renal afferent pathways in the rat: a pseudorabies virus study.

Retrograde tract tracing studies have indicated that dorsal root ganglion cells from T8 to L2 innervate the rat's left kidney. Electrophysiology studies have indicated that putative second-order sympathetic afferents are found in the dorsal horn at spinal segments T10 to L1 in laminae V-VII. Here, the spread of pseudorabies virus through renal sensory pathways was examined following 2-5 days post-infection (PI) and the virus was located immunocytochemically using a rabbit polyclonal antibody. Two days PI, dorsal root ganglion neurons (first-order sympathetic afferents) were infected with PRV. An average of 1.2, 0.8, 2.1 and 4.4% of the infected dorsal root ganglion neurons were contralateral to the injected kidney at spinal segments T10, T11, T12 and T13, respectively. Four days PI, infected neurons were detected within laminae I and II of the dorsal horn of the caudal thoracic and upper lumbar spinal cord segments. The labeling patterns in the spinal cord are consistent with previous work indicating the location of renal sympathetic sensory pathways. The nodose ganglia were labeled starting 4 days PI, suggesting the involvement of parasympathetic sensory pathways. Five days PI, infected neurons were found in the nucleus tractus solitarius. In the present study, it was unclear whether the infected neurons in the nucleus tractus solitarius are part of sympathetic or parasympathetic afferent pathways or represent a convergence of sensory information. Renal denervation prevented the spread of the virus into the dorsal root ganglia and spinal cord. Sectioning the dorsal roots from T10-L3 blocked viral spread into the spinal cord dorsal horn, but did not prevent infection of neurons in dorsal root ganglion nor did it prevent infection of putative preganglionic neurons in the intermediolateral cell column. The present results indicated that renal afferent pathways can be identified after pseudorabies virus infection of the kidney. Our results suggest that renal afferents travel in sympathetic and parasympathetic nerves and that this information may converge at the NTS.