Do renal afferent fibres modulate the function of the contralateral kidney?

Denervation of one kidney has been shown to induce a prompt decrease in sodium and water excretion from the contralateral kidney. The present study was designed to clarify whether this response is due to suppression of a tonic inhibitory renorenal reflex. Experiments were performed in anaesthetized cats in which the renal nerves of the left kidney were transiently blocked by cooling and the effects of this blockade on either kidney were studied in three different groups of animals. The decrease in sodium and water excretion from the contralateral (right) kidney observed in the sham-operated group (intact dorsal roots) was still present, and substantially unchanged, in the second group of animals in which the ipsilateral (left) dorsal roots from T9 to L4 were cut. In the third group of cats, bilateral dorsal root section entirely abolished the response of the contralateral kidney to renal nerve cooling. These experiments demonstrate that the contralateral decrease in sodium and water excretion is due to the block of afferent renal nerve fibres which project bilaterally to the spinal cord.