Extrinsic innervation of the rat kidney: a retrograde tracing study

To determine the exact modalities involved in the innervation of the kidney, the present study used a nerve-tracing method with horseradish peroxidase-wheat germ agglutinin (HRP-WGA) as the tracer. Multiple injections of HRP-WGA were made in each of the left kidneys of 12 rats while another four had the HRP-WGA either dripped onto their intact renal mesothelial surface or injected intravascularly. After retrograde transport of the tracer to neurons of origin (i.e., 72-h survival), the rats were briefly perfusion fixed, tissue was removed, and cryostat sections were cut. The free-floating sections were reacted by the tetramethylbenzidine technique. Retrogradely labeled neurons were found in the celiac, bilateral inferior vagal (nodosal), and ipsilateral dorsal root (90% in T12-L1 DRG) ganglia. More labeled neurons were present in the combined vagal ganglia than in the combined DRG within each animal. This labeling was specific compared with the controls (HRP-WGA uptake via intraperitoneal or vascular routes). The celiac ganglion had many labeled neurons; however, no labeled neurons were seen in the dorsal motor nucleus of the vagus, nucleus solitarius, nucleus ambiguus, or any other brain stem structure after renal injections of HRP-WGA. This study has determined that the sympathetic nervous system (celiac ganglion) provides the only renal autonomic efferent (motor) innervation, and the nodosal (inferior vagal) ganglia appear to provide more renal sensory innervation than do the dorsal root ganglia.