Renin and the sympathetic nervous system

Upright tilting and intravenous furosemide seem to be very effective stimuli for sympathetic release of renin, and fruitful models by which to identify the afferent and central pathways involved. The renal nerves probably form the efferent branch of a reflex system whose afferents lie in the vagus nerve and whose receptors are stretch receptors in the cardiopulmonary area. The operation of the reflex is such that decreased stretch of the heart results in increased activity of sympathetic nerves, especially the renal nerves. This system with its probable ability to increase the release of renin and thereby to increase aldosterone production, provides an attractive, though as yet speculative, monitor and regulator of blood volume.