The spinal course and medullary termination of myelinated renal afferents in the rat.

Myelinated afferent fibers, recorded in the left renal nerve of rats, were antidromically activated by discrete electrical stimulation of the cervical spinal cord and the caudal medulla. The lowest thresholds for activation of these fibers were found in the most medial portion of the ipsilateral fasciculus gracilis. This region of minimum threshold continued rostrad through the nucleus commissuralis. Based on threshold vs depth contours, fibers appeared to terminate in the ipsilateral nucleus gracilis and nucleus solitarius. Myelinated fibers could be activated by punctate pressure on the renal hilus. Action potentials generated by hilar pressure collided with antidromically-conducted action potentials elicited by electrical stimulation at cervical levels. We conclude that myelinated renal afferents carry information from intrarenal receptors, via the dorsal column system, to both visceral afferent and dorsal column nuclei.