The reno-renal reflex; evaluation from renal blood flow measurements.

Stimulation of the intact renal nerve bundle at a frequency of 5 Hz was found to affect not only the blood flow of the ipsilateral kidney, but also the contralateral kidney responded with a 15% reduction in its total and regional renal blood flow. If the nerves were cut proximal to the stimulation electrodes, the ipsilateral kidney, as before, responded with a reduction in its blood flow, but now the contralateral kidney remained almost unaffected. If, on the other hand, the nerves were cut distal to the stimulation electrode, meaning that only efferent nerve fibres will be activated, the contralateral kidney responded with the same 15% fall in its blood flow. If the afferent fibres of the ipsilateral kidney were stimulated as before, but the contralateral kidney was denervated, no reduction of the blood flow of the contralateral kidney could be established. It was furthermore noted that stimulation of afferent fibres resulted in a prompt rise in the systemic blood pressure with subsequent normalization after interruption of the stimulus. It is concluded that the general sympathetic tone is determined also by receptors within the kidneys. The signals reach the central nervous system via afferent fibres, and act to increase the sympathetic tone with concomitant rise in the systemic blood pressure and increased efferent renal nerve activity with subsequent reduction of the renal blood flow.