Not much focus has previously been placed on the afferent sensory innervation of the kidney and its physiological importance in the cardiovascular regulation compared to the efferent sympathetic innervation of the kidney. However, recent studies in man showing long-term depressor effects following renal nerve ablation, which reduces both ERSNA and afferent renal nerve activity (ARNA), have highlighted the afferent renal nerves and their possible role in hypertension. The first part of the chapter on the afferent renal nerves will be focused on the afferent renal nerves and their role in cardiovascular regulation in healthy animals. As will be discussed in more detail below, in healthy animals, activation of the renal sensory nerves elicits an inhibitory renorenal reflex response consisting of increases in ARNA, the nerve signals going from the kidney to the neuraxis, causing decreases in ERSNA, which in turn result in natriuresis (Figure 6.1). As will be discussed below, in many pathological conditions, the nature of the renorenal reflexes is switched from being of an inhibitory to an excitatory nature.

FIGURE 6.1

Increasing renal pelvic pressure stretches renal pelvic wall tissue and activates renal mechanosensory nerves. The resultant increases in afferent renal nerve activity decrease efferent renal sympathetic nerve activity which in turn increases urinary (more...)