1. In anaesthetized cats, reversible nenal nerve denervation (cooling of the renal nerves on one side at 4°C for 16 min) was performed and its effects on haemodynamic and excretory functions of the ipsilateral and the contralateral kidneys were studied. 2. Renal nerve cooling did not cause any change in arterial pressure. Slight increase in blood flow, no change in glomerular filtration rate and a large increase in water and sodium excretion occurred in the ipsilateral kidney; simultaneously, no change in blood flow, a slight and transient decrease in glomerular filtration rate, and a significant decrease in diuresis and natriuresis were observed in the contralateral kidney. 3. Ipsilateral and contralateral renal changes were equally evident in the early (minutes 0 to 8) and late phases (minutes 8 to 16) of the cooling period. 4. When renal nerve cooling was repeated after surgical denervation of the contralateral kidney all contralateral effects were abolished.
1. Anaesthetized cats were subjected to two 10 min trials of head-up tilting spaced 30 min. Arterial pressure, heart rate, blood flow to an innervated kidney and to the contralateral denervated one, and renin release from both kidneys were measured. 2. The same haemodynamic changes and comparable increases in renin release from innervated kidneys occurred during both episodes of tilting when cats were subjected to sham cervical vagotomy between the two tilting trials. 3. Bilateral cervical vagotomy, performed after the first episode of head-up tilting, did not affect the haemodynamic response to the change in posture, but significantly and markedly reduced the increase in renin release from the innervated kidney. 4. After sino-aortic denervation a marked and sustained arterial hypotension occurred during tilting, and the postural increase in renin release from the innervated kidney was even greater. 5. In no condition, even during the marked fall in blood pressure in sino-aortic denervated cats, did head-up tilting increase renin release from the denervated kidney. 6. It is concluded that maintenance of arterial pressure during tilting is mainly due to sino-aortic reflexes, whereas vagal reflexes are mostly responsible for the postural increase in renin release.