Renal afferents and hypertension.

The kidney and the autonomic nervous system are linked through renal nerves. Activation of efferent renal sympathetic nerves leads to changes in renal vascular resistance, renin release, and Na(+) and water retention. Evidence also exists indicating that the kidney is not just a target organ of sympathetic activity, but also acts as a sensor. Afferent renal nerves have been shown to carry information from renal chemoreceptors, which respond to changes in the composition of the interstitial fluid environment, and mechanoreceptors, which monitor hydrostatic pressure changes within the kidney, to the central nervous system. These afferent renal nerve inputs alter the activity of central integrative neuronal circuits that normally give rise to command signals that influence the function of effector organs. Renal receptors, through their connections at different levels of the neuraxis, are able to reflexly influence not only cardiovascular function through changes in sympathetic nerve discharge to a variety of vascular beds and the hypothalamic release of vasopressin, but also the function of the kidney. This increased sympathetic activity and hormonal release induced by activation of afferent renal nerves has been implicated in hypertension of diverse etiologies.