A direct projection from the kidney to the brainstem.

The double-labeling, fluorescent dye technique was used in order to demonstrate the extent to which the central processes of renal afferent neurons directly project to the brainstem. One injection of a fluorescent dye was placed in the cortex of the left kidney of male rats, and a second injection of a different dye was placed into the lower medulla. The results demonstrate that some of the renal afferents directly project to the medulla but not to higher regions of the brain. A total of approximately 8% of renal afferents were typically shown to have direct projections.