Reduction of renal nerve activity by volume expansion in conscious cats

In conscious cats with intact or denervated baroreceptors volume expansion of 5-15% of blood volume was performed with dextran and isotonic sodium chloride. Renal sympathetic activity (RSA), electroencephalogram (EEG) blood pressure (BP) and heart rate (HR) were recorded. RSA was reduced by 25-85% in 10 experiments out of 11 by volume expansion both with dextran and isotonic sodium chloride. Reduction of RSA could not be related to different states of wakefulness as indicated by the EEG, so could only be caused by volume expansion, although no quantitative correlation could be detected. No differences were observed between animals with intact and denervated baroreceptor. In most experiments BP and HR decreased during volume expansion up to -25 mmHg and up to -23 beats/min, respectively. The degree of BP and HR reduction could not be related to the degree of RSA reduction. The results suggest that changes in RSA might be involved in the renal response to volume expansion.