Renal sympathetic nerves reach nearly all nephron segments and renal vascular elements to regulate Na+/electrolyte balance, renin release, autoregulation of renal plasma flow (RPF) and glomerular filtration rate (GFR) in normal and stressed conditions. Disordered brain regulation of renal function may cause chronic salt retention and hypertension, and may contribute to acute kidney injury, when shock and sepsis markedly augment sympathetic activity, cutting RPF and GFR. Although we know much about the renal actions of sympathetic nerves and catecholamines, we know little about the brain neural circuits which control sympathetic output to the kidney.