1. Four Macaca fascicularis monkeys were bilaterally sympathectomized by removing the thoracic sympathetic chain from the middle cervical ganglion to the T-6 sympathetic ganglion. This was done chronically, allowing adequate recovery time. While under light pentobarbital anaesthesia, the animals were then subjected to blood volume expansions with isotonic, isooncotic dextran or to head-out immersions. Seven immersions and seven volume expansions were carried out.

2. With immersion, there were significant increases in blood pressure, central venous pressure, urine flow, sodium excretion, potassium excretion, glomerular filtration rate, percentage of filtered sodium excreted and free water clearance. Although blood pressure and central venous pressure initially increased during the first immersion period, heart rate continued to increase with the immersion, while blood pressure and central venous pressure remained constant. Volume expansion caused an increase in central venous pressure, urine flow, sodium and potassium excretion, osmolar clearance, free water clearance, percentage of filtered sodium excreted and glomerular filtration rate.

3. Since these results with both the immersions and volume expansions were not qualitatively different from those observed in control animals, it is concluded that cardiopulmonary sympathetic afferents are not necessary for the renal response to head-out immersion or blood volume expansion in the non-human primate.

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